Using CFA634 V2.2 with a Raspberry Pi


New member

I've got an old CFA634 V2.2 that I'm trying to interface to a Raspberry Pi v2.0. The Pi is able to supply 5v to power the LCD (via J2) but after hooking up the Pi's transmit line to the 634's DATA_IN (J2), the display shows seemingly random characters when the Pi sends data. I'm pretty sure I've configured the Pi's serial parameters to the right baud rate and I've closed jumper JPE. I've tried jumper JPB both open and closed with similar results. In trying to understand the possible causes, I found the following statement in the 634 module specification document:

Logic (+5 volts):
Supplied through J2: 4.75 volts minimum, 5.0 volts nominal, 5.25 volts maximum
Supplied through DB9 connector using the on-board regulator: 9 volts minimum, 15 volts maximum

Is this statement referring to the voltage needed on DATA_IN? As I understand it, the Pi only supplies 3.3v on the transmit line. Could this be the cause of the behavior I'm seeing or should I be looking elsewhere?

Would greatly appreciate advice and/or pointers
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CF Support2

The CFA634 really likes it's baud rate to be as close to it's selected input as possible. My understanding is that the RasperyPi is pretty good at outputting the baud rate that you tell it.

The "high" on the serial line of 3.3v is most likely the problem. The module is not seeing a high as a high - you'll need to get the logic level up to 4.5 ~ 5.0 for it to interpret the input signal correctly.
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