Thanks to www.chibios.org, I’ve just learned of two low-cost development boards based on the STMicroelectronics STM32F07 microcontroller. You might be interested in these boards because one costs $15.57 and the other sells for 39.95€. The lower-cost board is from STMicroelectronics and is called the STM32F407-Discovery kit. You can buy it from Arrow Electronics in the US and they had 84 boards in stock when I wrote this post.
The other board based on the STMicroelectronics STM32F07 microcontroller is called the Olimex STM32-E407 and it is available direct from the vendor.
Both boards employ versions of the STM32F07 microcontroller. The version on the STMicroelectronics’ dev board is the STM32F407VGT6 microcontroller with 1Mbyte of flash memory and 192Kbytes of RAM. The Olimex STM32-E407 is based on the STM32F407ZGT6 microcontroller with the same complement of Flash and RAM. The big difference between these two microcontrollers, according to the STM32F07 data sheet, is the number of I/O pins and the number of analog channels for the on-chip, 12-bit A/D converter.
Consequently, there are some I/O differences between these two boards. The STMicroelectronics STM32F407-Discovery kit includes a MEMS motion sensor and 3-axis, digital output accelerometer; a MEMS audio sensor (omnidirectional microphone); eight LEDs; two pushbuttons, and USB OTG (On the Go), and unpopulated headers using an STMicroelectronics proprietary footprint. The somewhat more expensive Olimex STM32-E407 dev board includes an Ethernet port, a USB Host port, a USB OTG port, an SD card socket, LEDs, pushbuttons, and unpopulated Arduino-footprint headers.