shmups.system11.org • View topic - GBS 8200/8220 CFW Project http://shmups.system11.org/viewtopic.php?f=6&t=52172 shmups.system11.org Shmups Forum FAQ Search Register Login It is currently Tue Nov 10, 2015 9:56 pm View unanswered posts Board index » Shmups » Hardware View active topics GBS 8200/8220 CFW Project Page 1 of 9 [ 242 posts ] Go to page 1, 2, 3, 4, 5 ... 9 Next Print view Previous topic | Next topic Author Message dooklink Post subject: GBS 8200/8220 CFW Project Posted: Tue Nov 11, 2014 9:01 am Here is a project that I've been working on for the GBS scaler boards. I'm not well versed in posting these kinds of things, so this could be a bit confusing for the moment. I'm also new to the forums but have been reading a lot of information on here and getting into CRT retro gamming as I mentioned in the introduction thread . Joined: 07 Nov 2014 Small Summary Posts: 85 I have created some code for a Raspberry Pi running Rasbian to interface with Location: Australia any GBS board (8200 or 8220). This programs the register settings in the scaling chip, the TVIA Trueview 5725, directly via I2C at 3.3V. The on board MTV230GMV microcontroller, sometimes going by rebadged labels such as GBS800MV, is bypassed by shorting the jumper on Port 8 (P8). This puts it into In System Programming (ISP) mode, which means it can't interfere with the custom settings being programmed. Here is a short list of the improvements I have been able to get working thus far: Pure line double mode, allowing correct 30Hz drop shadows with no interpolation YPbPr component output, with Sync on Luma included Resolution changes, including 576p50Hz Correct 50Hz input, this works on some versions of the original firmware and not others Finer control of the scaling and image position Control of the image processing chain to adjust all sorts of image quality settings Over sampling of the output using 4x oversampling of the pixel/dot clock I have created some python and bash scripts that allow for a black and white interactive menu from the Raspberry Pi's composite acting as pure Luma. This has allowed me to create, save and recall settings for 240p and 480i RGB to 480p YPbPr, as well as 288p and 576i RGB to 576p YPbPr. I am in the process of documenting my code for posting on GitHub. In the meantime I'll post more information to see what interest others have in this work. This is a picture of my testing setup at the moment: 1 von 14 10.11.2015 23:00 shmups.system11.org • View topic - GBS 8200/8220 CFW Project http://shmups.system11.org/viewtopic.php?f=6&t=52172 Raspberry Pi (Raspbian) gbs-control example code For Release v0.3 Probably the last version I will make. This adds colour correction, dynamic de-interlace, extra video modes and component sync level adjustment. For Release v0.2 An updated version is now avaliable with 1080p 60Hz RGBHV and YPbPr modes added. All YPbPr modes should now use a correct sync level. See the change log below or on github for a small summary. For Release v0.1 I have finally put together a package that can be easily installed on a fresh install of Raspbian on a Raspberry Pi. This is to allow others to try out the settings I have made if they want. I'm not sure if I will be able to update this at all, I'm now going to concentrate on reading and writing to the GBS micro. I'm sure the quality of the code is very poor seeing as this is my first time doing this sort of thing. My GitHub repo is here: https://github.com/dooklink/gbs-control Installation: The readme on the GitHub page should cover how to use this. All you should need to do is install Raspbian on a Raspbery Pi and run the following command while connected to the internet: Code: curl https://raw.githubusercontent.com /dooklink/gbs-control/master/install- gbs-control.sh | bash Connections: There are four things required for this to work: 1. Composite video port connected to Green RCA Luma input of the GBS board 2. I2C SDA, SCL & GND connected between the Pi and Port 5 of the GBS board (Do not use port 6!!) 3. A usb keyboard, wireless is fine 4. P8 jumper shorted on GBS board Here is a pinout diagram for the rev2 and later boards: http://pi.gadgetoid.com /pinout/i2c Compatibility Notes: For Release v0.3 2 von 14 10.11.2015 23:00 shmups.system11.org • View topic - GBS 8200/8220 CFW Project http://shmups.system11.org/viewtopic.php?f=6&t=52172 Shouldn't cause and issues with any models, but bug reports are welcome For Release v0.2 I've added code to detect rev1 Model B boards. This should allow for direct installation on these boards, but I haven't testing this myself. For Release v0.1 I was trying to make sure the scripts would work with any version of the raspberry pi, but I have given up on that for now. This means you will need a rev2 Model B or any other raspberry pi. I believe only the very early rev1 Model B use the old i2c port, most should use the new port. Also, the user needs to be the default "pi" as I have assumed the home directory is "/home/pi". Change Log: SPOILER: SHOW Component Video Sync Levels (edit: added 13/06/2015) As you may know RGB signals are normally 0.7v pk-pk. A component luma signal (or SOG) have an added 0.3v sync level underneath, making the signal 1.0v pk-pk total. The GBS board has a resistor that sets the maximum output range of the video DAC. This is set to create 0.7v pk-pk signals only, which explains the issues with component thus far. Version 0.3 of gbs-control has a sync level setting to adjust this to attempt to get the best compromise between sync stablility and brightness levels for a standard GBS board set for a 0.7v signal. A value of 194 should achieve 0.3v sync levels, but with reduced video range. However, there is a hardware mod to get correct 1.0v pk-pk output. The formula in the programming guide is: Vout = (1.25 * 2046 * Rout) / (846 * Riref) Where Vout is the max voltage level before double termination, that is 0.7v * 2 to get 1.4v. Rout equals the output resistance, 75 ohms. And Riref is the setting resistor, normally 150 ohms on the PCB. This give a value 0f 1.48v pk-pk max for the normal GBS boards, which is slightly above the expected 1.4v pk-pk. If the total series value of the Riref resistance can be changed to around 111 ohms, then the output voltage would be 2.0v pk-pk, or 1.0v pk-pk when terminated. I have fitted a switch to one of my boards with a 430 ohm (100 + 330) resistance that can be switch in parallel with the PCB 150 ohm resistor. This gives the option of 150 ohm for 0.7v signals, or 111 ohm for 1.0v signals. So those that want better component output can try this. Use the default sync level of 146 in the menu for 0.3v sync with this mod. The Iref resistor is shown below, it is connected to the sixth pin along, and then to ground. 3 von 14 10.11.2015 23:00 shmups.system11.org • View topic - GBS 8200/8220 CFW Project http://shmups.system11.org/viewtopic.php?f=6&t=52172 Hardware Information & Comparison 4 von 14 10.11.2015 23:00 shmups.system11.org • View topic - GBS 8200/8220 CFW Project http://shmups.system11.org/viewtopic.php?f=6&t=52172 Original Firmware Problems The original firmware had many issues for use with low res gamming content, particularly for us PAL 50Hz users. I have seen and read about lots of these issues before I started work on my custom settings. The most obvious is the deinterlacing applied to progressive 15Khz sources. I have been able to get around this issue with an odd glitch. I have not been able to get 240p input working without using the deinterlacer, but It can be tricked into doing an exact line doubling. And by disabling the vertical scaling engine and setting the output resolution to exactly double the input the results are very sharp. The most frustrating for myself, was the 50Hz performance. I knew this board was hit and miss with 50Hz, but fagins YouTube video review of the SLG-In-A-Box shows that the unit can work with a 50Hz Megadrive. But that's when my trouble started. I bought a GBS board locally from a PC & Arcade shop. The first board I bought worked with 50Hz input, but had insane amounts of noise in the image. Here are some images from that board with Sonic spinball on the Megadrive. 50Hz Noise: 50Hz Noise, with just sync signal: 5 von 14 10.11.2015 23:00 shmups.system11.org • View topic - GBS 8200/8220 CFW Project http://shmups.system11.org/viewtopic.php?f=6&t=52172 And yet here it is in 60Hz: I got that board exchanged for a replacement. The new board was better, but not by much.