Moving towards PCBs and SMDs

Next I took a proto board and built a row of 16 LEDs which I would control with the Discovery board. Soon I noticed that the loosely hanging wires from the Discovery board were a compete mess. They were highly irritating to work with. I had to integrate the microcontroller onto the proto board to get rid of some of the mess.

Since the Discovery board used ARM Cortex M4 microcontroller, made by ST, I decided to stick with those for now and browsed through their catalogue. I wanted to have a microcontroller with fewer pins and lower price point, so I wouldn't feel so much mental pain whenever I managed to destroy one of those chips. After several nights of research my choice ended up being STM32F373CBT6. It is maximum of 72 MHz and has 48 pins and all the peripherals and features I might need. This includes additional touch sensor support, if I ever wanted to experiment with it (which I did want to but didn't have the time to do it). This microcontroller has only 24KB of SRAM and 128KB of flash, but that should be enough for what I'm doing with it.

I soldered the chip onto one of those small green adapter boards which enabled me to use it with a standard proto board.

The picture to the right shows two brown proto boards. The one on the left has the MIDI input and output circuitry as well as the 3.3V regulator feeding the microcontroller with proper voltage. The board on the right is the one containing the row of LEDs as well as the microcontroller. I even added an 8 MHz crystal next to the green adapter board, but I was a bit too optimistic thinking it would actually work so far away from the microcontroller. The four digit LED screen was something I also was going to get up and running, but before I managed to do that, I already had the next revision of the board in the works. I ended up running this iteration of the board in 8 MHz, which was driven by the microcontroller's internal clock. I used the STM32F4Discovery board's SWD output connector to program this board.

The middle picture on the right shows a close up view of the adapter board with the STM32 soldered on it. The last picture shows a closeup shot of the MIDI I/O circuit.

At this point I cursed the dark gods of electronics because of how quickly those proto boards fill up. Also the issue with excessive amount of wires was still there, even though not as prominent. It was time to move into using surface mount devices and printed circuit boards…