We are using the LCD in a battery operated embedded system and eventually if the batteries become low and if we attempt to write an image or upload fonts and the write fails (due to battery brownout) any subsequent attempts to repeat the process will fail even with a restored good battery.
In other words, when writing an image or uploading a font to the LCD and a brownout occurs, any future attempts to write an image or font to the LCD will also fail. I can reproduce this behavior using your GMod# application using a variable power supply. In my application when the LCD is in this failure state attempting to write an image or upload fonts will results in the watchdog timer going off and I get the FE D4 so it appears the LCD is going off in the weeds and resetting due to a corrupted directory structure or some other invalid internal state error.
Note that most of the LCD commands are functional, controlling LEDs, turning off/on the back light, even writing text to the LCD all are functional. Only commands that directly change the directory structure cause the LCD to reset. Uploading Fonts/images for example cause the LCD to reset. In our application we must be able to upload images to the LCD thus causing updates to the LCD directory structure.
My questions are;
1) Can you use the steps provided below and reproduce the problem and suggest a work-around or provide a firmware fix?
2) There are commands to get the size and to get the directory structure. Is there another command (perhaps undocumented) that can verify the directory structure is not corrupted?
3) Other suggestions?
Steps to reproduce the problem;
1) Using MogD# and a variable power supply and communicating to the LCD via a serial port.
2) Delete the Directory structure.
3) Upload 1 font to slot 1.
4) Write out text with Font in slot 1 to verify correct operation. "hello world" for example.
5) Start the upload of another font into slot 2 and while it is upload cause a brownout by adjusting the power supply down till the LCD resets. Yes - the command will fail.
6) Readjust power supply to 5V - Turn power off and back on.
7) Attempt to write font again. Get "There was a problem uploading the font to the device". In my application I am getting the watchdog timer reset and also note that MogD# is also getting the FE D4 from the LCD. See the Serial trace below.
So from what I can tell the LCD Directory Structure is corrupted and now any commands that would write to the directory will cause the LCD to reset and issue an FE D4. The only way I have found to overcome this is by deleting the current directory and starting all over.Please feel free to contact me via email or phone and we can discuss in more detail if you like.
Below is a serial comm trace from the MogD# application once the LCD is in this failure state. Note the FE D4 at the end.
Thanks for taking a look,
Mark.
Note : I have added an attachment with a serial trace of the MOGD# app attempting to upload a font once the memory of the LCD is corrupted.