I’m just about done with my OLED display. I bought it for about £15 a while back for a Raspberry Pi project. It promised to be a great high tech, but cheap[ish] solution for running the Pi near headless with just a two line glow in the dark text display. Useful … for … something.

Anyhoo, I managed to sodder[sic] the thing together and, to cut a long story short, it cracked into life on the Pi’s 5 volt rail. The default message offering a welcome. Brill.

Now, to get other text out of it. For this I needed to program the Pi’s UART to output a nice serial signal … But it is IDLE high whilst the PICAXE is idle low. To make matters worse the Pi is 3.3v logic compared to the PICAXE expecting 5v. Problem? Not for a budding hardware hacker.

Or so I thought. I shoved the signal through a buffer, checked it on my xlabproto’s UART snooper (“hello world” looked good), inverted the signal using a spare NAND gate, jacked it up to 5v using a purchased converter board. Result: nowt. ARSE!

I thought if I could change the PICAXE to IDLE high then all would be well. It’s involves changing one character from ‘N’ to ‘T’. But this required the PICAXE proprietary serial cable. £15+p&p for the USB version. All that to change one character. To hell with that.

I tried using a USB to rs232 cable cobbled with an Rs232 to 3.5mm jack but no joy. Either the thing is broken or requires exactly the right cable. However, it is cheaper to just order an LCD display and ditch this. What a pain. Just because they charge £15 for a £2 cable.

So I’ve been a bit crest fallen as this was my first hack project. I’ve been feeling like giving up. Bit today I remember I’d ripped a mobile phone to bits and extracted the binary dot matrix display. It’s generally reasonably well documented online. Probably a good thing to tinker with. It will be a magnificent achievement if I get it running. But I’d feel more confident if I’d got this lousy OLED working first.

Anyway I’ll try documenting progress here. I know you’re just dying to hear all about it.


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