Happy Happy Joy Joy!
The mailman brought a new display. Cheapskate I am I took the display with the most bang for the buck – at least I thought. The display here is a 0.96inch 128×64 OLED blue/yellow with 3(!) interface options: 3wire SPI, 4wire SPI and 2 I2C. And then the problems began…
I wanted I2C mode because I’m a little limited on i/o’s on the FeatherFona. The boards factory setting is 4wire SPI and for the other modes you’ll need to resolder a tiny 0 Ohm SMD resistor on the back (or just bridge the two pins). Did that and connected VCC, GND, SDA/DIN, SCL/CLK and fired up the Fona. Nothing.
Also waveshare has actually a wiki with a spec-sheet of the SSD1306, a schematic and a user manual for the module it’s of no use for people like me. They only mention 4wire mode and with not a single word that you actually have to connect 7 wires for a 2 wire I2C.
And I usually don’t have the time to go through all the specs nor the deep electrical knowledge.
So a bit of research, a bit of fiddling and long story short – the pinout:
GND - GND (obviously) VCC - 3.3V (spec says somewhere 5V via dc/dc regulator but I'm not sure if there is one and I don't have 5V anyway) DIN - SDA CLK - SCL CS - GND D/C - GND RST - 5V or #4 (actually the SSD1306 spec says: keep HIGH during normal op, pull LOW for reset)
For the reset pin I’ll see what happens if I just wire this to VCC and never pull LOW. I mean: I never want to reset the display controller. I reset/power down the whole FONA which should also reinit the display controller, amirite?
So module is working and now I finally know what a blue/yellow display is. b/y doesn’t mean you can freely choose color. b/y means theres a row of yellow pixels at the top and the most part of the screen is blue. This is a kind of odd design but one could argue that you’ll often have some menu title in the top anyway.
So that’s for the display. I now have 2 options to choose from which was important for me to be more flexible with the actual design of the phone. Speaking of design I now have a fairly good idea which direction I’m going. Time for some electro etching 🙂
Besides all this I’ve got a job opportunity so I think I’ll need to get my hands dirty with some java frameworks in the next few days.