March 9, 2025

Olimex STM32-E407

I found one of these on Ebay and won the bid for $20.00 (and $5.97 shipping) on 11-18-2020. This board is based on the STM32F407 chip (specifically a STM32F407ZGT6, which has 1M of flash and 192k of ram in a 144 pin package. The processor is an ARM Cortex-M4. They are sneaky about the actual clock rate, saying only that it delivers 210 DMIPS (whatever they might be). The CPU probably runs at 168 Mhz, maybe 192 Mhz.

It has a barrel connector for power and they say any DC voltage from 6 to 16 will work. I use a 12 volt supply and it works fine.

One end of the board has a 20 pin JTAG connector. It works just fine to connect only 3 wires to a SWD type ST-Link gadget, making the connection as follows: 

pin 7 (TMS) to blue wire (STlink SWDIO)
pin 9 (TCK) to yellow wire (STlink SWCLK)
pin 14 (GND) to green (GND)
STlink orange (3v) not connected

The board has a bunch of pins available via headers that you could solder on. Alongside the 20 pin JTAG connector is what Olimex calls a UEXT connector

The board has an ethernet connector. And it has a micro-SD slot!

The board has two USB connectors. Both are mini-USB. 

USB-OTG1 is FS (closest to ethernet connector).
USB-OTG2 is HS

Where is the serial console?

This is not available in a handy way that I can find yet. On CON3 we have: 
D0 = PB7 = usart1_rx
D1 = PB6 = usart1_tx
Usually pins A9 and A10 are used, but B6 and B7 are an eligible alternate location, we will just have to set up the GPIO settings accordingly in software. Searching the schematic, I find that A9 and A10 have been dedicated to USB OTG signals, so that is that.

CON4 nearby has a labeled GND.

Note that CON3 and CON4 have two rows of pins, but the rows on both are connected together. The same is true of CON1 and CON2

Feedback? Questions? Drop me a line!

Tom's Computer Info / tom@mmto.org