Quote:
Originally Posted by _dx
Hi guys!
I gonna participate in custom firmware development for GBS8200.
The main question is: where is i2c registers information in datasheet http://file.yizimg.com/420856/2013041613555642.pdf
Somebody have the information about configuration registers of Trueview5725?
May be someone have another(full) version? |
You need the programming manual, there's a link here:
http://shmups.system11.org/viewtopic...52172&start=30
The TVIA 5725 uses I2C address $2E. Using the Raspberry Pi I2C commands, they support a 7 bit I2C address (as bit 0 is read/write indication) so you divide the address by 2 to get $17 for the device. If, like me, you have a rev 1 RPi, use I2C bus 0 not 1 in the commands/scripts.
The TVIA5725, like other video devices requires multiple banks, you write to offset $F0 the bank address, 0-5, each bank has a set of registers.
The manual is scattered. Some related settings are on different banks so you need to bank switch.
With regard to how to configure the device, that has no easy answer. Look at the number of functional blocks in the device.
I think we need to concentrate on a few blocks:
- ADC sampling and sync recovery
- Scan rate conversion for 50-60 Hz
- De-interlace (Bob/weave selection)
- 3D noise reduction
- Scaling
- Video enhancement (maybe)
I'm concentrating on item 1, The falling edge of the sync is absolutely critical for timing of a video device. Any jitter screws up the whole chip. It's used for standard identification, clock generation and sampling of the video. I currently use a 680 ohm resistor to couple the sync in, it works but it slows the sync signal, I will convert the Amiga 5V CMOS signal to LVTTL soon.
The Amiga and a number of other consoles, the Megadrive was mentioned, have Dc coupled video outputs. Black level is 0.6-1V approximately. Most devices expect black level to be 0V. A 100nF capacitor at the ADC helps but you can get droop issues. Coupling the video output with 220uF capacitors can help but you can adjust black level clamping
Once the device is synchronised, and correctly samples the video, I can move on. There will be an element of 'suck it and see'.