LK402-12 RS232 query and no response

[gvines]

We use LK402-12 displays in a product and have several units that after setting the serial number the lcd stops sending information back. Setting the serial number may not be relevant.
Our test program sets up the serial port, then reads the module type and determines the configuration. After we receive this one byte response, all subsequent commands (such as request version, serial number or even requesting the module type a second time) result in nothing being sent back. Our code times out after 100ms, which we have increased to 1 second. We also tried checking for extra bytes but see nothing amiss until it stops.

This code is used in our product and we have many units that work fine. Is there any reason why the unit would stop responding to queries?

Thanks!

[gvines]

This seems to be just the request serial number function (which I notice was dropped in the updated LK402-25 product) and the request firmware version (for which the 402-25 product says only works in TTL mode) Were these features dropped prematurely? These particular units were near the end of the -12 product life. We will probably change our product to not use these as we are migrating to the new display anyway, but we would like to understand the cause.

[Raquel]

Hello gvines,

Thanks for your post.

The displays should continue replying to query commands. Can I please get you to try the succession of commands you send to the display using uProject? Please let me know if the display acts the same.

As per the changes in Read/Write Serial Number commands, we have actually expanded this to Read/Write Customer data. Instead of two bytes, there are now allotted 16 bytes of whatever information the customer wants to store in the display's memory (non-volatile), this can of course include the serial number as before.

Thanks,

[gvines]

Unfortunately we no longer have the units. We changed our app to not query the LCD and shipped the units. We now only have the newer displays in stock...