Firmware 1.6 problem on CFA-635


We have detected a problem in our system that have been introduced with the new firmware 1.6 in the CFA-635 USB display.
I do not know why, but the display is not working properly with our software.

Is it possible to buy this display with the old firware version?
Or is it possible for us to downgrade to the 1.4 firmware?

This would buy us some time to change the software to fit the new firmware.

Thank you


John Melin
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CF Support2

The v1.6 firmware has a slower clock speed. This was done to make the CFA635 series more robust in terms of power supply fluctuations. We have seen where code does not follow the recommended methods of packet reconciliation, there are issues being encountered. Particularly when the supporting code is all timing based.

It is possible to order the CFA635 series loaded with the v1.4 firmware. There is an additional charge as there is a component that needs loaded. You can send an email to for pricing and ordering information.
USB LCD Displays - Graphic and Character LCDs with a Keypad


New member
I had this problem too. It turned out to be a bug in my code which was tolerated by 1.4 but not 1.6.

My code uses ping packets to resynchronize if a packet is lost or gets an error response. I read in the datasheet that packet data is limited to 22 bytes but didn't notice that ping packets are limited to 16 bytes of data. I was sending ping packets with 22 bytes of data and this worked just fine with 1.4 but 1.6 was returning errors (or ignoring them, I don't remember now).

Changing my ping packets to 16 bytes fixed this.

Note: the datasheet always restricted pings to 16 bytes, it just wasn't enforced in 1.4. It was my mistake missing that in the datasheet.

Maybe this will help you.