Matrix Orbital Corp

We have been using the VK202-25 display in several applications for the past year, with some issues along the way. Several displays have been sent back for repair after they stopped responding, with no explanation of what was found to be wrong with them. This latest issue is one that I have the most clear understanding of the circumstances that preceeded the problem:

Display set to 19200 baud. External 5V power supply connected via the DB9 connector.

We were actively writing text to the display when the communication lines were opened. When the communication lines were re-connected, the display showed garbage, but the garbage changed at the times I would expect the text on the screen to change. This led me to believe that the baud rate the display was set to may have inadvertantly changed. I installed a jumper on pins 5 and 6 of the keypad connector and I was then able to display text on the screen normally.

However - 4 of the 5 horizsontal bargraph characters were no longer correct. I checked our software to make sure that we were sending the bargraph initialization command (0xFE 0x68). I then performed the following experiment: I changed one of the custom characters, then displayed a bargraph. The custom character I created showed up in the bargraph. I then sent the bargraph initialization command and displayed another bargraph. The original garbage character showed up in the bargraph. This would lead me to believe that the display firmware has incorrect characters that it is copying over to the custom character set whenever I call the bargraph initialization command.

My questions, then:
1) Can I leave the jumper on pins 5 and 6 of the keypad connector permanently to prevent the baud rate from ever being re-set?
2) Are the characters that became garbage in fact stored in the firmware, or are those really just another set of user-definable characters? The manual is a bit confusing on this - Page 14 shows bargraph charactes at 0x10 - 0x18, although it says the user-defined characters are at 0x00 - 0x07.
3) How was I able to change the bargraph characters in the firmware?
4) How do I restore the bargraph characters stored in the firmware to their original settings?
5) If I was able to corrupt the bargraph characters, what else could be accidentally corrupted? Can the PIC firmware be re-written via the RS232 port? And if so, what protections are there against doing so?

Thank you.

Hello...

Any functions that are related to memory chip allocation can be "permanently saved" if a memory chip lockdown is performed. This will not allow any write access to the EEPROM. The problems you are experiencing with the display may be related to "noise" type scenarios. If noise is interfering with the data sent it is very possible that bits are being dropped or even changed, thus "garbage values" appear. To be perfectly honest the bargraph problems you are experiencing are something I haven't seen before. Since custom characters are stored in the memory and most of the problems you are encountering are directly related to the memory chip, maybe the memory chip is faulty?? If you wish to email me directly regarding some of the problems you are experiencing, please feel free. My direct email address is myero@matrixorbital.ca If llok forward to hearing from you.