Despite making a template to ensure fitment I made a mistake with orientation/footprint of the 30pin connector, and it is already in production so it is too late to change. It should be fine for testing, I will have to mount the connector backwards.
Month: July 2020
AT050TN22 via VGA
I have done this previously, but this another run with the AT050TN22v1 and its matching VGA driver connected to the external VGA of the PC110 docking connector. Display is slightly cut off because the screen is just in there temporarily. This just to remind myself and demonstrate again that the screen is in fact okay and has good contrast and can properly display all the colours.
These are just captures from the external VGA port of the modetest outputs, it is useful as quick reference when looking at the outputs when generated on the LCD without switching back and forth while changing XR values.
PCB V2 Planning
I had attempted previously to try and identify the values for each pin manually with a logic analyzer and colour bands same as Mr.Taka has attempted previously, but as we both suspect this leaves room for error. Additionally the assignments can change based on XR values for colour width and other settings so this makes documenting even harder when it is not certain which mode is active sometimes.
I tried another approach which maybe was already tried. I attempted to work backwards from the OEM display Citizen pin-out comparing the recommended connections with C&T for similar screens and take those as the assumed pins and then move forward to the TFT15 values.
On PCB V1 only line line for sure was bad. I noticed that usually RED was showing as Yellow, and Red+Green=Yellow, so I realized that one of the RED pins on PC110 has to be connecting to Green pin on VGA. Identified it as PC110#21 to VGA#25 (G2). I cut the trace on the PCB and I now had no cross mixing of colours, but they were still very wrong, likely because if misorder MSB to LSB as well as missing lines.
My approach purely from documentation and not practical testing leads me to believe that PC110#21 is RED2, which is consistent with the issue I was having.
PCB v1 Results
The only immediate issue was that I forgot to connect VCOM pin 46, so I had to put a jumper on. Pin6 VCOM was okay. Based on previous issues I believe each one supports alternating lines.
As expected there are some issues with the colour, it seems that it may be specific to red but requires some more investigation. I consider the test successful though in that I did not see any “noise”, the picture was perfectly stable with no flicker.
The physical fitment was also good, however I wrecked my last 30pin connector so I had to use one salvaged from the old CSTN which is why I have the screen positioned strangley.
I got the correct adapter in and I have successfully dumped the contents of the flash. As expected the video bios is there. I am certain I could modify the XR registers in the vbios binary just like C&T BMP and it would work. The challenge now is how to flash from software.
Analyzing the contents of the flash should help me confirm I am reading it correctly through the flash chips CUI (Command User Interface), which is something I am still working on, based on the dissassembly of xpatch.exe
I did not get the [email protected] from this yet, it had a sticker that said REV0.33
BIOS – Initial Look
To make the TFT conversion complete, we need to modify the ROM bios to have the correct configuration values for the new display.
After some research I learned of the BMP (Bios Modification Program) provided to OEM’s by Chips&Technology for customizing the CT65535 video bios. It is simply a program that allows you to customize the bios binary. I was not able to find the BMP file for a CT65535 only a CT65545, however it was easy to see what it was doing and confirm that I had located the correct bytes within the video bios I had dumped from C000h.
I am expecting to find a copy of this video rom on the intel flash chip. I do not have the correct TSOP-40 for my ChipProg-40, however I will receive it next week and will dump the contents of the flash to confirm its contents and locations.
For my purposes I am fairly confident I will be able to edit the values, reprogram and put the chip back on. This is not ideal though so the goal is to flash/patch it with a program. I have been reviewing the xpatch.exe to understand how this is possible. I will not attempt anything until I have verified I can backup and program the chips off the board.
This is a disassembled version generated by Sourcer. This is VERY preliminary. I am also investigating with IDAPro 5.0 Free, which properly opens a MZ executable.
As I have previously mentioned, at times I was having what I suspect were signal integrity issues due to the messy wiring through the adapters, wires, breadboard etc running at 25mhz. I wanted to get a proper connection in place and know the signal quality is okay before investing time in trying to perfect the image on the display.
I am inexperienced with PCB design, and I was being impatient and wanted to get SOMETHING quickly so I was certainly sloppy with this layout and made a gamble on the colour wiring. I am fairly confident the MSB’s are correct, so at a minimum I can cut the other traces to at least use it to see if signal quality has improved and work on physical placement. The pin header is to power the led backlight and tft gate drivers (vcom/vgl/vgh) externally until I can verify what we need to put on the PCB itself. The boards are on the way and will be delivered in a couple days.
Some progress with connecting the AT050TN22 v1. As with previous tests, this only has the MSB for each colour connected. I will be sending out for a pcb prototype this week to test further. It looks quite good in person, and there is no flickering.
The style is very sloppy, this was put together in a rush very late to debug the chip. I may improve it later on as it did prove helpful. The assembly version written at https://garakutaen.sakura.ne.jp/ is excellent, however my assembly knowledge is not strong enough to make some of the changes I needed so it was easier to write in C.
The current values configured are for the AT050TN22 V.1 but are not confirmed to be correct.
You can use this program at your own risk. If you have any questions leave a comment.
UPDATE 2020/07/18: I have found some of the original OEM tools for debugging so the need for these custom programs for debugging may be no longer. I am going to maintain a page of all the tools I can find HERE.