Problems with CFA635-TFE-KU h1v2 u2v0


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I have a problem with a few pieces of CFA635-TFE-KU h1v2 u2v0. It seems related to this thread.


  1. OS is Linux
  2. Device is detected correctly, VID/PID match. This implies USB communication is OK.
  3. Your original program from this page works partially:
    • Program starts, displays welcome banner
    • Sets port and baudrate correctly (/dev/ttyUSB0 @ 115200)
    • Displays 4 "Timed out waiting for a response." messages on console in place of the ">>>This is line 1<<<" up to ">>>This is line 4<<<" on LCD
    • Enters readkey loop
    • Displays keypresses correctly.
  4. What's interesting, clear parameter works correctly - it does clear the screen, but still does not display lines of text.
  5. My own software hangs waiting for complete frame, I'm rewriting it do dump data on-the-go in both directions.
  6. Any operation other than clear seems to restart LCD (backlight goes off,LCD contents disappears for a fraction of second, backlight goes on)

All Pre-Rockworks CFA635 work fine for me.

Anything I can do to fix it?

----- EDIT ------

I did some debugging & tracing with delays between commands:

  1. Cmd 0x06 works, reply comes. LCD blanks.
  2. Cmd 0x0E works, reply comes, backlight changes.
  3. Cmd 0x1F does not work, no single byte of reply comes, LCD resets to factory defaults (C-F banner & full backlight)

Old version of LCD works as expected.

----- EDIT ------

Cmd 0x16 works, so I'm able to eventually write something to LCD...
Hope this helps.
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USB LCD Displays - Graphic and Character LCDs with a Keypad


New member
----- UPDATE -----

After being off for 1 day, display refuses to execute Cmd 0x16 (LCD does not update, CFA sends no reply, LCD does not reset to defaults) on the very same program that worked during my last post... Now I'm stuck completely.

What's interesting, after stuck cmd 0x16, controller stucks on every other command until I powercycle it. Then again 0x06 works, 0x0E works, 0x16/0x1F stuck. 0x16 just stucks, 0x1F resets LCD & stucks.
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CF Support3

Sorry to hear that you are experiencing difficulty!

It is important to remember that since the Rockworks controller has been implemented into this product, any use of command 22 (0x16) will need to take this note in to account:

"Any command sent specifically to the controller Samsung S6A0073 will need to be reviewed / modified for
the commands / registers of the Rockworks RW1067. Please contact the Crystalfontz Engineering Support
Team at for the RW1067 datasheet."

It is concerning tho that the module is not functioning at all now as expected. It is difficult to make an assessment or diagnose the module in the field, but if you would like to have our Engineers here examine it as part of an RMA we would be happy to do so. Simply complete the RMA request form at the link below:

This will create a support ticket with our engineering support staff and we will be able to better assess your concerns from there!

If you have questions, please don't hesitate to send an inquiry to for further assistance.

Thank you and have a great day.