axe033 board and Raspberry Pi

[gran_dad]

Hi,

Maybe this isn't quite the forum to answer this, but I have scoured around the interweb trying to find answers. So I offer my apology first.

I have an axe033 display board which works well with the little 08 Picaxe projects I have made; SO I thought I would try getting it to display info from one of my Raspberry Pi.
I am attaching it to the Pi serially using just power/ground/TXD with level shifting on TXD up to 5v Now I know the board works at 2400, 8 bits no parity and 1 stop bit.
Try as I may, I cannot get the board to display anything sensible. I've tried sending it 0xfe, 0x31 followed by a delay to clear the screen (or ASCII 254,1) which sometimes results in either garbage on the display, or "This Is Message x", or even "Serial / LCD Display" (I think) on line 2, with what looks like placeholders for time and date below on line 1
It seems to be that either some/all of the port settings are not correct, or I am completely barking up the wrong tree.

Can anyone shed more light on the port setting I should use, also the command bytes in the manual are in ASCII i.e. 254 , 1 Should I send ASCII 254,1 or hex values i.e. 0xfe, 0x31?

Any constructive help would be most welcome 'cos I can't afford to lose any more hair

TIA
Martin

 

[Technical]

Welcome to the forum.
level shifting and polarity inversion may well be required - the TX signal from rpi must be idle low.

decimal or hex doesn't matter - it is the same number to rpi, just the way us humans read them that varies!
They are not ASCII, so 254,1 means two bytes - value 254 then value 1.

 

[gran_dad]

Welcome to the forum.
level shifting and polarity inversion may well be required - the TX signal from rpi must be idle low.
<snip>

Thanks for the info Technical.
I have tried using polarity inversion (sounds like some thing Dr Who would say ) using the circuit attached, but to no avail

I believe it should do the job, but I am still getting garbage. I have tried various combinations of resistors; nothing seems to work.
Have you any further words of wisdom which may help?
The program I am attempting to write is in Python, so probably not appropriate here.
TIA
MArtin

 

[gran_dad]

Ahhhh! OK,
I have now tried "minicom" on the Pi, and it talks to the axe033 board fine; just got to work out how to send the board the control characters it requires now.
So it is as I suspected; my programming skills have let me down (again!)
Sorry to waste your time Technical
Martin