Actual date: 2018-12-17 and 2018-12-18
Since my USB device efforts have not led anywhere so far, I diverted my efforts to get an OLED up and running, still on the STM32L4 platform. Eventually, it will be nice to have a Solo key with an integrated display!
Scott Mabin recently added I2C support to his HAL, so I got everything ready quickly. It DID NOT WORK!!!!
Well. First, I bought a very cheap soldering iron and did a horrible job (first solder experience in over two decades) of attaching the pins to my 0.91" 128x32 OLED (with an SSD1306 chip). Still, did not work!
Then, I discovered the 0.96" 128x64 OLED with the same chip was already pre-soldered... again, DID NOT WORK!
The next day, I finally followed both Conor's and Scott's advice in trying different I2C addresses. A quick search suggested using
0x78 (which is 2*
0x3c, which all the data sheets mention) for cheap Chinese clones such as mine, and ta-daa! Success!