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Year 2017 - Synthesis

Written by cafealpha no comments
Synthesis ... this is the kind of blog article posted at the end of December in normal blogs, but since this is not a normal blog, and that I can't respect any schedule for it, let's prepare this article at the beginning of January

Last year started well with an order of Gamer's Cartridge from IGK, who is administrator of Dezaemon DB homepage. More than administrating Dezaemon DB, he is also a dezaemoner who (among other titles) developed Biometal Nemesis, which deserves its youtube link in this blog :)
Biometal Nemesis - Click above if you like shmups

I really like the style of this Dezaemon game ! Thank you very much IGK for creating such gem

Thanks to IGK, it was possible to finish support of Saturn Floppy Disk Drive on Save Data Manager : initialization of this device is slightly different than with internal backup memory and backup memory cartridge, and consequently was causing troubles on various configurations such as no backup memory cartridge inserted, but floppy disk connected, etc. Fixing all possible patterns wouldn't had been possible without kind help and beta testing from IGK. Thank you


Save Data Manager (version around 2017/01/30)
Configuration when this screen was taken was no "backup memory cartridge inserted, and floppy disk connected", which was causing troubles because among other things, unavailable device in the middle of devices table wasn't supported.

Additionally, this was the occasion to add virtual floppy disk support on Gamer's Cartridge, making Saturn considering a floppy disk drive is available, even if not physically connected.
Main purpose of this feature is to add 5 more save and load slots in Dezaemon 2, which, in addition of the 5 slots on backup memory cartridge, makes possible to manage up to 10 saves into a Dezaemon 2 session directly from a single SD card 
I don't remember exactly what was the trigger which started the addition of this feature, but I think that a suggestion from IGK like "it would be cool if floppy disk would be supported by Gamer's Cartridge too" and me "Ah yeah, that's a nice idea ... how many save slots do you want ?"

After that, IGK continued to surprise me by asking his friend beebaraka to draw a Dezaemon 2 themed label for Gamer's Cartridge ... As a result, I received images for two labels, which I personally consider as the masterpieces among Gamer's Cartridge label collection
My preference goes to the white-themed label, but I suppose it's just a matter of personal taste.

Dezaemon 2 themed Gamer's Cartridges
Like shooting games ? Like DIY ? Theses cartridges are designed for you

In parallel of theses Dezaemon 2 adventures, generous contributors helped in dumping firmware of some exotic Saturn cartridges, and were successfully added to Pseudo Saturn Kai Save Data Manager.
Most relevant dumps were for X-Terminator cartridge, and Urawaza Dataro cartridge : first one is a cartridge with extended support for cheat codes, especially with extra controller allowing in-game search of cheat codes. Later one provides special save data for several (around 34 IIRC) Japanese games. Special thanks to Madrom for providing dump of this cartridge !

All the points below contributed to prepare the "20170423" release of Pseudo Saturn Kai. Warm thanks to all contributors who could make it possible !


Second half of the year mostly concerned cheat codes addition to Pseudo Saturn Kai. It started in June (or May ... I don't remember correctly) from a Gamer's Cartridge user asking when cheat codes will be available in Pseudo Saturn Kai ... this reminded me I still had to finish that until next release


First working version of cheat codes
hander, with USB transfer support
It's not visible on this picture, but many polygons weren't
drawn because of performance issues.

Unlimited time cheat code working : it took me around
one month to fix missing polygons, because of unoptimized
implementation of cheat codes handler), but I did it
 
Cheat codes kept me busy for six solid months, basically in understanding to manage cheat codes in a similar way as is it done on Action Replay firmware, optimizing critical code, importing codes list, finishing cheat codes related interface, testing several games, etc.
That's honestly a hard work, but this was also an occasion to add in-game USB transfer via USB dev cart. Thanks to this, the basis in order to fix or improve cheat codes is ready  Proper PC software for cheat codes detection is still missing, but hopefully this will be done someday.

Akumajo Dracula-X illustration with Maria's inifinite jump cheat code.
This game was a nasty one regarding cheat code support, with very
tight CPU and RAM left for cheat codes handler. This was an occasion
to develop many cheat codes debug features

Summer was also the occasion for me to officially end manufacturing and support of USB dev cart : after 5 years involved in this adventure, I considered it was enough, because :
 1. USB dev cart interests basically nobody
 2. In the rare cases USB dev cart interests somebody, it is usually used for closed-source projects
(But there are notable exceptions where USB dev cart contributed to Saturn open source projects. Big thanks to theses concerned peoples for making Saturn homebrew scene brighter )



I'm hesitating about the timing for next Pseudo Saturn Kai release : should I take some extra months in order to get proper cheat codes support for most popular games ? Or should I release it under few weeks with minimal cheat codes support (around an handful of games are currently tested and working), and hope to receive some feedback from users, so that I will eventually know which games need their cheat codes to be fixed ?

That's a very difficult choice : cheat codes is a niche feature (as everything else regarding Saturn !), so I shouldn't hope a lot of feedback. On the other hand, adding a cheat codes edition screen, and allowing cheat codes input on user side is (IMHO) a mistake too : maybe a motivated user would fix and/or add codes for some games, but rarely theses codes will be publicly available for everybody else, and in the other cases, user will simply consider Pseudo Saturn Kai cheat codes as a broken feature.
Let's see ... I honestly don't have any precise idea when next release should be done. Any suggestion regarding this is welcome in the comments

Generally speaking, I'm tired about Pseudo Saturn Kai maintenance : I started it around two years ago (yes, largely over than nine thousands hours !!!), edit: that was around three years ago (I though we were at the beginning of year 2017 ), am finally seeing the end of my TODO list to realize that ... majority of users shifted to hardware ODE, or simply left the scene without any last final word ...

Well, whatever it may be, I continue development of Pseudo Saturn Kai because I went too far to stop so near of the end (that's quite a pragmatic argument, sorry), but also (and that's the most important), because that's a nice hobby, which is important in order to keep a balance between private and work

Also, my first steps in Pseudo Saturn Kai maintenance were made during my hospitalization for cancer, and keeping such hobby during theses hard times was worth gold. I don't know (and don't want to know) how things would had turned without my Saturn hobbies.

BTW, things concerning my health are getting well : I'm still undergoing periodical screening, which all were OK last year  Last year was the celebration of 3 years all right after surgery, which is not bad for a cancer with 50-60% 5 years survival rate

Pokemon Go still not allowed in hospital.
Fortunately, usage Saturn dev laptop isn't forbidden



To finish this article on a rant note (sorry if you went here for some final positive note ), I would like to say "thank you for nothing" to Rhea/Phoebe development team rmenu author. (← updated on 2018/06/20)

Why ? Reason is that I would like to add a rmenu equivalent to Pseudo Saturn Kai, but don't have any technical information to implement it, and it's not like I didn't asked about theses informations, but simply didn't received any relevant reply from concerned developer(s).
For a semi-commercial product, I can understand to keep schematics, source codes and other development resources private. But I don't request disclosure of theses resources, and just want some minimal information for interoperability, which isn't publicly available, and that's a pity.

Why is that a pity ? Because some cheat codes will certainly not work by having rmenu running between Pseudo Saturn Kai and Saturn game. I know there's the solution to use rmenu's full boot, which does a system reset of nearly everything (except Rhea/Phoebe, obviously) after selecting a game, so that cheat codes can be enabled after that ... but I really don't know anybody motivated to do this messy setup : everybody is using the rmenu's quick boot solution, right ?


Pseudo Saturn Kai's rmenu, dated 20151214.
Latest version have some major improvements,  such as
scrolling title of select game, etc
Because of lack of Rhea/Phoebe API, this feature is disabled.


I'm personally (and honestly) not concerned about this problem : my modded Saturn + USB dev cart are enough for my development needs, and I don't want to pay for a device costing an arm and a leg (plus a kidney when buying from ebay ...) and then having to do the reverse-engineering job for it after that ! So unless I got external help, clean support for Rhea/Phoebe will be done ... without me

From what I could found from static analysis of rmenu itself, version is checked by seeking to the last available data sector of the CD track, and game is selected by seeking to sectors just before that last available one.
After that's it's difficult to guess what data should be expected from Rhea/Phoebe without testing on real hardware. And reverse-engineering is usually a sluggish and hard work (I estimate the remaining as around a two weeks course ... and hope this to be a pessimistic estimation), and really would like to spend this time to other projects funnier.

2018/06/20 update : there will be proper support of Rhea/Phoebe image selection in Pseudo Saturn Kai, and consequently an user-friendly way of enabling cheat codes when using theses ODE
Very big thanks to Deunan Knute for the great job, providing the technical informations and everything else
And also I would like to thank privateye for contacting Deunan, his patience and great help in beta testing

Read more Year 2017 - Synthesis

Pseudo Saturn Kai 6.074 released !

Written by cafealpha 2 comments
Pseudo Saturn Kai 6.074 released ... more than three months ago  Sorry for the late news, but that's still some quite acceptable delay in comparison to frequency I post articles in this blog

The release was initially announced on SegaXtreme forums, because it is my favorite forums for Saturn things (more than 11 years I registered to it !
Big thanks to the forum moderation/maintenance/support team for their steady good work ). Also the news was announced on SegaXtreme first ... because writing an article there takes less time than writing an article on my blog
So since I'm a lazy person, let's slightly arrange this article from what I wrote on SegaXtreme forums !


What's new in this version ? Well, there's basically, not a lot of major features (sorry !), but fix of a critical bug affecting Gamer's Cartridge, and addition of some "minor, but that I wanted to add someday" features.

______________
Features for Gamer's Cartridge users

Indirect Dump
: Dump cartridge (boot cartridge, or official memory cartridge, or any other cartridge) by compressing its contents to internal backup memory, and then extracting it to SD card when Gamer's Cartridge is inserted.
Because of small size of internal backup memory, it may be required to repeat the "insert memory cartridge → Indirect Dump → Turn off Saturn → Insert Gamer's Cartridge → Indirect Dump → Turn off Saturn" cycle several times, but at the end cartridge is dumped
Requires some motivation and free time on user side (It took me 45 minutes in order to dump my good old very first official memory cartridge), but this way of dumping doesn't requires to unsolder cartridge memory chips, which is the most important for me !
Note : if you are the lucky owner of Saturn FDD, then floppy disc is used instead of internal backup memory, and consequently dump is significantly faster and simpler.


Left : Screen display after compressing dump data
to internal backup memory
Right : Screen display after writing dump data from
internal backup memory to SD card
Theses pictures were taken on Indirect Dump's first successful test

One extra application of this feature was to dump ROMs from legacy cartridges such as X-Terminator, Satellite, ST Key and "8MEG memory cartridge". Curious people wanting to test theses cartridges theses ROMs can found them available for flashing (at your own risks) in Pseudo Saturn Kai Save Data Manager.
Special thanks to A Murder Of Crows, AtariBorn and SaturnGuru who dumped their cartridges ... and reported many bugs from early versions of Indirect Dump feature 

 
Indirect Dump development : the cut scenes
Left : dump data corruption (see below for details)
Right : Dump file CRC check error. Fortunately, only dump
computation routine was buggy, and dump feature itself was working


Save Data corruption bugfix : This corruption problem concerns saves on Saturn internal memory, with save data size making save sector allocation table finishing exactly at the end of a sector. Very few games are concerned, and the only example I could find so far is Albert Odyssey.

I found this problem when testing Indirect Dump : data compressed then written to internal save memory wasn't then correctly read and decompressed to SD card.
I initially thought this problem to be caused by Indirect Dump itself, because at the time I had this problem, I just finished to mess with data alignment error when preparing indirect dump's compressed data, so thought that this was the next bug to fix regarding Indirect Dump
Quick investigation showed that contents of read data wasn't as expected, with a small portion of data being same as data at unrelated offset ... so maybe a problem when compressing and adding header etc to Indirect Dump save data ? It took me then a around one hour of testing and code review until I was sure that culprit was actually not Indirect Dump itself, because re-read of save data didn't matched with written save data !
Then, testing Indirect Dump with same input data and virtual memory cartridge disabled worked as expected, which 99% confirmed that problem was located on virtual memory cartridge side !

So yes, "virtual memory cartridge" actually manages save data handling for all backup devices (internal save memory, memory cartridge, and even Saturn FDD too) : this is possible because Gamer's Cartridge hooks Saturn backup library at relatively high software level.
In comparison with 1:1 hardware emulation of save memory cartridge, this has the advantage of being free of capacity limitation inherent to memory cartridge's chips, and also allows to store save data individually on SD card (two files per save, vs big file containing all saves for 1:1 cartridge emulation). On the other side, all the save data handling software has to be re-written, so care has to be taken when re-implementing it

So, this is quite an uncomfortable bug I have to face : save data are corrupted when being written to internal save memory, and Gamer's Cartridge was released around 6 months before, with consequently cartridges potentially corrupting save data in the wild.
Fortunately, while being hard to find, the bug wasn't hard to fix  Basically, this was a timing error when updating current save data block ID, as described below :


Internal Save Data corruption related source code
Left : before fix
Right : after fix



Since I really didn't want to fix half of the bug (and having to fix the remaining half on other release), next step is to add a test bench tool for internal save data memory access !
"Test bench" is a program that automatically tests a lot of patterns for a given function or module. Ideally, all major modules should have their test bench, but in the real world, making test bench programs takes time, so programs are usually manually tested with 2 or 3 patterns, and then developer prays for all other patterns being bug-free 
... And to tell you the truth, this test bench was the largest one I wrote so far  It's not impossible a bug to be still hidden in an untested pattern, but anyway I'm quite confident about the reliability of internal save data support now 

Here is how test bench screen looks like on my dev environment :

SatLink and Yabause couple showing test bench screen.
SatLink and Yabause : my best friends when testing Saturn programs


Screen copy above was taken after fixing internal save data support, and I forgot to take a similar screen copy when bug wasn't yet fixed ... latest Save Data Manager CDROM's + Gamer's Cartridge with firmwave 6.037 should display error in test bench screen, so it would be funny to try it ... maybe someday 
BTW, Test Bench is still available in Save Data Manager CD-ROM (it took me a bit of time to add test bench screen, so didn't wanted to remove it after fixing internal save data corruption bug !), but this test bench screen requires a trick in order to be accessed : did you found it ?

That's all about internal save data corruption : I fixed it, and checked a lot of patterns about internal save data access, so similar problem shouldn't happen in the future !
Additionally, I didn't received any feedback from users about this bug, so let's hope it didn't corrupted game saves elsewhere than on my dev laptop



Autodump : Automatically dump saves from internal backup memory to SD card, so that they can be restored in the case they are lost because of depleted CR2032 battery, or save data manipulation error, etc.
With this feature, you won't have to say anymore "I lost all my saves because of that $%QTY@!#% CR2032 battery" 
Since this feature uses SD card, it is available on Gamer's Cartridge only. And no, I won't write save data into Action Replay's cartridge flash ROM : flash ROM chips are not designed in order to be written frequently, hence using flash ROM as read/write storage area may prematurely brick your Action Replay cartridge.
If you're not convinced about flash ROM limited write cycles, I can make some "cartridge self destruction" feature that would continuously write and erase random data to flash ROM, but don't claim that your cartridge no longer boots after that


An alternate solution in order to keep internal save data change the chip holding internal save memory to a FRAM one that doesn't requires battery to retain saves data, as detailed in db-electronics.ca.
(there are maybe other alternate solutions, so please let me know in the comments if I missed one)

The advantage of this FRAM mod is that saves are not lost when CR2032 battery is depleted. There are however several disadvantages :
 - This is an hardware mod, which requires to remove a chip, then solder another one, hence quite difficult to do.
 - CR2032 battery is still required in order to keep clock and language informations.

For being the developer of Pseudo Saturn Kai and Gamer's Cartridge, my opinion is a bit biased, but autodump is a better solution, because autodump is not an invasive mod (plug cartridge vs change chip on Saturn motherboard), and the FRAM solution doesn't allows to dump save data to modern media device. Anyway, I don't force you to like my projects, so if you don't like autodump, then don't use it


Virtual Floppy Disk Drive. Simulate Saturn Floppy Disc Drive (FDD) behavior, with save data stored on SD card.
This feature Worked fine with Dezaemon 2, which can now handle 10 saves at once (5 saves from cartridge, and 5 other saves on FDD ), but I didn't tested for other games using FDD, so any feedback is welcome.
This is a feature available on Gamer's Cartridge only too. Thanks to this feature, floppy disk access is available without having to plug any floppy disk drive to Saturn 



______________
Features for Action Replay and Gamer's Cartridge users

Proper support of FDD in Save Data Manager : Save Data Manager now supports both two partitions of Saturn floppy discs for all common operations such as copy, move, delete, import, dump, etc.
Special thanks to Dezaemon DB for big assistance in beta testing


Backup devices informations from Save Data Manager :
First device is internal backup memory : the easiest to handle
Second device is backup memory cartridge,
unconnected (zero partitions detected) in this picture
Third device is FDD : two partitions, wrong unit ID returned,
and always set at third position in devices information
array, even when cartridge is not available.
Basically, FDD is a real trouble-maker when trying to handle backup devices



Save Data Manager development cut scenes : trying to format FDD
(format for both two partitions is displayed in a single picture)
Don't worry about the horrible display of error
messages : it's (finally) improved in version 6.074


Soft Reset Patch
: Change the "A+B+C+Start key combo" soft reset from "exit to multiplayer screen" to system reset. This idea is not from me, but from neuroacid (rmenu developer).


More saves to import from Save Data Manager
. The most noticeable addition is saves from Urawaza Dataro cartridge, containing quality saves for Japanese games. Special thanks to Madroms for dumping the cartridge, and providing me its dump file 


Other
: Fixed many bugs, and added other bugs ... the usual routine 


(Not a software feature, but) future users of Gamer's Cartridge may appreciate the couple of new labels, designed by beebaraka-sensei (twitter) for artwork itself and Dezaemon DB (twitter) for the final editing of the labels. Many thanks to them for the very good work !


Dezaemon-themed labels ... could you find out the odd label ?

The design on theses labels is themed on Dezaemon 2, and as you can see, the Dezaemon character on the game cover grew in the right way 
I personally do appreciate the white themed one





Before being asked "where are the cheat codes ?", please let me reply :)
Cheat codes support is still under development. Menu in order to select game and its cheat codes is 90% done, but the bit of code in order to apply codes is still TBD. I didn't touched this feature for around half a year mostly because of lack of free time, motivation, and being busy in developing other features. I plan to finish this for "next-next release" however.
Update three months after writing the explanation above : cheat codes on Pseudo Saturn Kai are working on few games !! 
There are many things remaining until reaching an "OK to release" state, but at least the cheat codes core feature seems to work, which is quite a relief for me :)

By the way, there's a trick cheat codes selection menu in Pseudo Saturn Kai 6.074 : did you found it ? It won't do anything else than showing games list and cheats for each games, so it's not worth spending more than 10 minutes in looking for the appropriates key(s) combo and timing however.


Yes, this release have (at least) two Easter eggs available Coincidence with release timing during Easter period ? I think not


Apart from cheat codes, there are many other things scheduled for future releases : I initially planned to release everything at once, but had to make this intermediary release in order to fix the save data corruption bug on Gamer's Cartridge, so stay tuned


PS : Special thanks to Stac for beta testing  All the features above wouldn't exist without his help !!!

Read more Pseudo Saturn Kai 6.074 released !

Bit shift in Saturn minimalistic C program

Written by cafealpha 4 comments
While making a Saturn program running directly from ROM, constraint is usually to have program as small as possible. Why ? Because I would like to make Pseudo Saturn Kai continue supporting Action Replay, which have limited ROM size

So, in that situation, I use homemade, minimalistic stdlib, containing usually only memcpy and memset functions, and everything goes well.
But for some reason, current program was begging for __ashlsi3 and __ashrsi3 functions.
... What's these things ? __ashlsi3 is an assembly function doing left shifts of data, and as you probably guessed, __ashrsi3 does the same, but with right shifts

No problem, let's ask my friend google, and copy & paste theses functions without minding about their contents Theses functions are standard functions provided by C library, so sources can be found here and there.


An example of what __ashrsi3 function looks like

A day after that, here comes the time to do basic testing of this ROM code
Let's first start with simple things such as screen display ...


Text display ... not as expected ?!

Hrm, it's probably a problem in my printchar routine ?

printchar source code : this is the core thing
behind text display in my programs


But that's a very long time I didn't touched this routine, which works well on Pseudo Saturn Kai, and works even better in vdp1ex from Charles MacDonald sample programs, because all my printchar routines come from there
But just in case of, let's try to tune one " <<3 " into " *8 " in the code above, and see if that changes something. Theses two operations are equivalent, so this should give the same result, but ... Saturn screen becomes all black

Okay, there's definitely something weird regarding that printchar, but I just re-used it as-is from other project, so what's going wrong with my it ?!
[...]
And then (finally) a light-bulb above my head appears Maybe there's something wrong regarding the __ashlsi3 and __ashrsi3 routines ?
And, yes there was something wrong regarding theses routines ... I wrote a paragraph about them on the first half of this article, so it would be surprising the problem came from somewhere else

In more accurate words, routines are OK, which is normal since they are written by people smarter than me But the calling convention of __ashrsi3 was not as my gcc was expecting ?
Well, that's just a guess from the display results, because it seems to display the same pixel 8 times on each row of a given character, which may happen when ignoring shift parameter in __ashrsi3 function.

Anyway, rather than finding in details what's wrong, let's fix the problem First, with assembly by hand, in desperately trying to change input parameter handling ... I don't remember exactly what I wrote, but that was something like pushing a register to stack, moving parameter to it, finally restoring register, putting nop instructions everywhere, etc ... nothing difficult, but over my extent in assembly programming

The result is ... a mixed success :

Trying to modify __ashrsi3 routine by hand ... well, it seems that
some shift values are not correctly handled


Okay, so let's re-ask google about that __ashrsi3 routine ... and a different implementation arrives in search results. Let's try it


__ashrsi3

And the execution result :

Execution result with second version of __ashrsi3 function

Yeah, it works this time !!! And don't ask me why, because I didn't took time in understanding what's different in that second version of __ashrsi3 function
And, rather than understanding why it works ... let's close that assembly pandora box before some other mystic bugs pop from it

I will probably see about this in the future, but that was absolutely out of the scope of today's programming, and in software world, too much digression leads to freeze of projects, which I would like to avoid in order to go forward to next pending project 

As a example, I started to adapt yeti3d engine to Saturn in 2010 (7 years ago !), and this ended in ... developing a SD card based memory cartridge for Saturn !
The point above is is not a joke : menus used in my yeti3d adaptation are the origin of menus used in Pseudo Saturn Kai, which shows the continuity (co-consanguinity ? ) in my projects. And after getting yeti3d working a bit, I really would like to load levels from something else than CD-ROM, which was from PC (via adequate link cable) on a first time, and which will (should ?) then evolve to SD card.
That would be cool to make a Saturn game not requiring to burn CD-ROM somedays, but before that I need to finish neighboring side quests


Evolution of my Saturn projects

To conclude this article, let's say it was terribly fun to see some bits of the internals behind C language
By the past, I remember I did something similar with my yeti3d adaptation, but remained at "C language level" : optimization done at that time was (IIRC, ) to avoid 4 bits shifts, because theses are not available in a single SH-2 CPU instruction. Avoiding 4 bits shifts was simply done by merging two fixed point operation in a single one (or something like that : I did this 7 years ago !), and this actually gave some improvements in 3D scene rendering Theses were the good times ... I sometimes think "I'm Getting Too Old For This Shit", but that's only to motivate to finish my old projects

But before that, Pseudo Saturn Kai, and then Kicad and Quartus are waiting for me


BTW, in the case you wondered about what was today's programming session, you probably guessed it was about exception handler addition to Pseudo Saturn Kai. This not a new feature, since it was available in Pseudo Saturn 0.83x ... in fact, I grabbed some sources from Pseudo Saturn 0.83x in order to implement this exception handler (thank you CyberWarriorX !) This exception handler will be available as a small add-don to cheat codes feature in Pseudo Saturn Kai next major release.

Read more Bit shift in Saturn minimalistic C program

[Dev journal] Pseudo Saturn Kai game loader weird bug, and its bugfix

Written by cafealpha 3 comments
(Note : this bug was fixed something like 3 months ago. Pseudo Saturn Kai I first released last month works well  )

First : of course, old versions of Pseudo Saturn (versions up to 0.832) work
But who knows what may happen when doing software engineering (and any other engineering in fact) : it's very common to break something without directly modifying anything to it !

So it happened : in December 2015, Pseudo Saturn Kai beta tester reported that it wasn't possible to load CD-R game.

data/images/20160325_loader_bug.tb.jpg
What game loader bug looks like.
disc_type=0x0003 means that CD-ROM authentication failed


As usual, I first asked if something was wrong on tester side  "Bad game dump ?", "Bad burn to CD-R ?", "Did you do something else bad ?", etc.
(I know that's a bad habit to suspect beta testers doing something wrong, but it sometimes help in fixing problems)

Beta tester was actually doing his job well, and bug couldn't be reproduced in next beta version, so I though it was caused by outdated intermediate file in build process (this happens, for example when I modify header file only : I'm too lazy to fix makefiles about this ) : cleaning up whole project and rebuilding everything prevents such kind of problem.

But I wasn't satisfied with such "half-baked" bugfix, and actually could hear it saying to me "I'll be back"


And, two months after that time, I receive same bug report from same beta tester ...
Well, at least, I didn't had to re-ask him if he tested correctly or not : it was clear that this was December 2015 bug returning back.


First, let's verify do simple things and try to reproduce the bug here : my "main" dev Saturn is a modchipped one that plays CD-R, even when firmware is reported not working. Trying with a "plain" (unmodded) Saturn actually reproduces the bug : cartridge boots, but definitely doesn't want to play CD-R.
In same conditions, let's try with an old version of the firmware : oh, it can play CD-R

So I could "feel" the bug, and its capricious nature.
"Typical" capricious bug is "uninitialized global variable" one, that reproduces after doing the same action twice, or after going to a given screen, returning back to another screen, and doing a given action.
Saturn has relatively few RAM available, and I don't want to use dynamic memory allocation on such "low specs embedded device", so such "uninitialized global variable" happens from time to time.

But this bug was even more capricious than "uninitialized global variable" one : same action reproduces the bug with a given firmware, but can't reproduce the bug with another firmware

First, since I have no idea about the cause of such bug, I added some debug screen that displays few details (= the return values of each functions called when unlocking the CDROM unit), and also some text-based logs, plus RAM dumps stored SD card : that was one of the reasons why I made SD card-based cartridge for Saturn : it allows to prepare bug report on user side

So I "just" have to wait until bug is reproduced with next versions, and beg for logs/dumps/etc on that time.
Of course, the bug reproduced, and of course ... logs/dumps/etc didn't helped a lot

data/images/20160408_sakura_6008.tb.jpg
Game loader failure screen.
Basically, it shows that something is wrong after
calling cd_move_sector_data_cd_auth function.


Fortunately, there are some explanations about Pseudo Saturn CD unlock exploit on assembler forums :
1. Use the Put Sector Data command to put a whole bunch of sectors into the CDB - all with FAD 150, Mode 2 in their headers.
2. Call End Data Transfer to push them into the selector.
3. Call Copy Sector Data, starting a copy of all those fake sectors into the selector that the Authenticate Disc command will be using.
4. Immediately (like 15 microseconds later immediately) call the Authenticate Disc command, specifying the same selector.


"Immediately" : firmware have to be fast on step 4.
And what changes in CD-ROM unlock code from a firmware beta version to another is basically its execution start address.
So I started to think : "maybe CD-ROM unlock code will work better if loaded from a constant address ?" : to do this, I moved all CD-ROM code to a separate stub, loaded from a constant address (0x06004000).

And bug didn't reappeared so far

Okay, this way of fixing things without a proper verification is a bit dirty
But it works, and that's the most important
(I suspect the cause of this bug related to SH2 cache : if SH-2 have to refresh cache during time critical section of CD-ROM exploit, code takes too long to execute, and CD-ROM exploit fails ... it's just a guess, and I realized about it after fixing it.)

Special thanks to Stac, Shazz and A Murder of Crows for beta testing
And special thanks to jhl and CyberWarriorX for detailing Pseudo Saturn's CD-ROM exploit ! This helped a lot in fixing this bug

Read more [Dev journal] Pseudo Saturn Kai game loader weird bug, and its bugfix

Pseudo Saturn Kai development : USB dev cart support

Written by cafealpha 7 comments
It's a long time USB dev cart is supported on Pseudo Saturn Kai, but it wasn't tested seriously elsewhere than my development environment.
... Until now

(Well, in fact, it was "until a couple of months ago", because I didn't had time to write this article earlier.)


So, a USB dev cart new user (Shazz) wanted to do some Saturn development : great


USB dev cart demo
USB dev cart demonstration video (youtube).
I used Shazz's USB dev cart to make this video,
in order to be sure it worked well before sending it to him.



His dev PC runs under Linux ... I personally use Windows only, so I can't guarantee USB dev cart + Pseudo Saturn Kai will work correctly.
"Maybe it will run fine with antime's ftx tool".
"Maybe"
Of course, it didn't worked

My first suggestion was "please use an old PC with Windows installed lol", but Shazz don't like such half-concession, and really wanted his USB dev cart to work directly on his Linux dev PC.
As an USB dev cart manufacturer, I agree with him.
As a programmer already busy with other projects and real life, I disagree ^^

But, Okay, Shazz is actually a cool and chatty guy, and sharing same mother tongue with me, so I will do it for him


The cause of the problem happening when using Linux + USB dev cart with Pseudo Saturn Kai is actually still unclear.
With original USB dev cart firmware (nicknamed as "blinking screen", or sometimes "epileptic screen"), executing a Saturn program with "ftx" utility works fine.
However, with Pseudo Saturn Kai installed, the same operation didn't worked and Pseudo Saturn Kai main screen was freezing (? or continuing doing menu things ? I already forgot about details about this bug  It's really time to write it on this blog before I forget it completely ...) instead of switching to uploaded program.

I suspected Pseudo Saturn Kai ignoring two successive commands from USB dev cart ("executing" a program is actually sending an "upload" command, then "execute from specified address" command), especially because Pseudo Saturn Kai can't check for USB I/O continuously : it "just" does it once every frame.

Since I really couldn't understand why this could cause that "upload, then execute" problem, I decided to countermeasure it by adding a new "upload and execute" USB dev cart command.
And on the same occasion, I also added the "à la carte" reset flags in this command : "one stone, two birds", as people in Japan would say ... I suppose that other people would rather say "one USB dev cart command to rule them all" :D


One more problem about this "Linux + USB dev cart + Pseudo Saturn Kai" problem was that I couldn't verify if everything is working fine or not.
Shazz was OK to do some beta testing, but he can only upgrade his USB dev cart via USB link, so "breaking" USB transfer would brick his development cartridge.
Around software development, I experienced enough Murphy's law and its corollaries to be sure it won't work on first try :
 - "If it can break, it will break"
 - "The less you test, the more likely it will fail on basic pattern"
 - "The more you test, the more likely it will fail on unexpected pattern"

So I added Pseudo Saturn Kai "demo" version
As its name suggests, it actually doesn't do anything special else than showing menus, but that's enough in order to test communication with PC.
Additionally, I also displayed some debug messages to screen when doing USB related stuff.

data/images/20160324_usb_test3.tb.jpg
Pseudo Saturn Kai demo version
showing USB activity logs on screen
First two lines logs USB dev cart firmware version
verification : even if used with old (not Pseudo Saturn Kai)
version of firmware, transfer utility works

After testing many buggy versions of the firmware, Shazz tried the "20160323_test4" test pattern with his "parallax" test program, and ...

data/images/20160324_usb_test4.tb.jpg
Could upload and execute libyaul example program
from Linux via USB dev cart and Pseudo Saturn Kai !



Thank you Shazz for testing Pseudo Saturn Kai + USB dev cart Linux support !


USB debug port related support is always a hell for me and cartridge users (may not work on a given OS, etc), hence there are no plan to add it in release version of my cartridges.
But even if it requires drivers and custom transfer software on PC side, debug USB connectivity is a must have when developing things on Saturn, so rather than dropping USB debug port, I plan to make a "USB + SD card interface" cartridge for Saturn developers only.
And of course, I still continue to manufacture USB dev cart

Read more Pseudo Saturn Kai development : USB dev cart support

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