STM32F373 Breakout

STM32F100 Breakout

STM32F373 Breakout Board V0.4

What is it?

This is a small (1" x 2") board with an STM32F373CCT6 MCU, 3.3V regulator, reset button, power LED, user GPIO LED, JTAG header, USB Device socket and most I/O pins brought out to SIP headers suitable for use in a solderless breadboard. With this board one can easily prototype small ARM Cortex M4F applications with minimum effort and expense.

What it isn't

This is not a full development system - you'll have to gather your own programming tools, power supply, I/O devices, etc. This is not an Arduino clone with all the low-level stuff already done for you. If you want to get by on the cheap you'll have to be familiar with setting up an ARM GCC toolchain as well as how to build your own copy of the latest OpenOCD JTAG downloader.



Software Development

The STM32 family of parts are supported by a variety of commercial IDEs, all of which are available in low-cost or limited free versions from the ST website.

I prefer to use open-source tools, so I've set up a development environment based on the GNU C compiler for ARM, available for free from Codesourcery or the Launchpad project. For downloading to the target I use either an STM32 Discovery board with stlink V2, or the excellent Black Magic Probe. To accelerate development I also use the STM32 Standard Peripheral Library as a starting point for my code and then optimize out the heavyweight functions as required. Links to all of these are here:

Design Resources



Testing of the boot mode flash loader on the STM32F3 Discovery boards suggested that the F3 bootloader was similar to the BID 4.1 type functionality found in many of the earlier STM32 parts, including USART1, USART2, CAN and USB DFU modes. After assembling the F373 breakout board it was seen that only USART1 appears to work (RX on PA10, TX on PA11). USART2 and USB DFU modes do not seem to be present (the 8MHz HSE crystal is never even started up). Checking the IDs in the USART1 mode shows BID 5.0 which is not detailed in the AN2606 Bootloader appnote at the time of this writing (12-12-12).

(01-04-13) We've conducted a disassembly of the STM32F373 system memory and confirmed that the bootloader in that device does not support USB DFU mode. Comparison vs the system memory in the STM32F303 (which does support USB DFU) shows that the code is about 1/2 the size and never accesses any of the registers associated with the USB peripheral. This represents a fairly significant deviation from the capabilities that are specified in the data sheet and reference manual for the STM32F373. So far, has not responded to questions about this so we have to wait for an updated AN2606 document for further details.

(05-01-13) ST did finally acknowledge that an early batch of STM32F373 parts was programmed with the wrong bootloader during the manufacturing test process back in Q3 2012. Those parts have apparently been cleared from the distribution chain and any new parts bought during 2013 should have the correct USB DFU-capable bootloader programmed into the system memory area. I have not confirmed this personally, but I have been told that it works by others who have bought parts more recently.

(09-19-13) I bought recent batch of STM32F373 parts and built up another breakout board. This one works just fine with USB in bootloader mode. Here's a table of what the markings and functionality are:

Purchase DateMarkingUSBSerial
Late 2012STM32F373CCT6 GH22T 9U CHN230 BNoYes
Mid 2013STM32F373CCT6 GH21P 9U CHN244 BYes???


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Eric Brombaugh

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