(Note, checkout CSTroN for a more complete writeup)
Looking back to the all 23+4 #LetsDriveLCD posts, I have covered positive and negative STN, positive and negative FSTN, color TFT, Eink, color CRT, bicolor LED matrix, and micro LED segment. Obviously there are lot of other type of screens that are not covered, like Plasma, EL, PNLC, etc. This time I am going to take a look at a common type of screen that hasn't been featured yet: CSTN.
CSTN is basically STN with color filter. Then I could just drive them like how I used to drive monochrome screens, right? Not quite. Mainstream processors no longer has native support for STN/CSTN interface, unless I go and use an older processor. I have been using STM32 + bitbang to drive STN. It's kind of good enough for STN, but not quite for high resolution CSTN. It's simply not fast enough. USB/ SD bandwidth, GPIO speed, and complications like FRC + dithering, they are all issues.
The solution is straightforward, use an FPGA. So here we are. VGA input, DDR2 buffering, FRC to 5bpc (32768 color), finally output to CSTN.
Checkout the videohttps://www.youtube.com/watch?v=hsehw-7-VTM
- Model: SX21V001
- Type: Color passive dual-scan dot-matrix
- Mode: CSTN Negative
- Resolution: 640x480
- Greyscale: None
- Controller: None
- Size: 8.2"
CSTroN GitHub: https://github.com/zephray/CSTroN
Screen datasheet: /uploads/blog/2018/1535734517689-sx21v001-z4.pdf