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The STM32F407 is currently one of the most powerful MCUs on the market and ChibiOS/RT offers an excellent device driver support for this platform. Now just a detail remains to be decided, which board to buy. Let's compare two cheap boards, the already popular STM32F4-Discovery and the newly released Olimex STM32-E407.
Both boards have a lot to offer and share an important detail: both are really cheap and there is plenty open source support for them, including ChibiOS/RT of course.
|Physical Dimensions||97 x 66 mm||101.6 x 86 mm|
|MCU||STM32F407VGT6 (LQFP100)||STM32F407ZET6 (LQFP144)|
|Crystals/Oscillators||8MHz HSE, LSE not fitted||12MHz HSE, 32768Hz LSE, 50MHz RMII|
|Flash / RAM||1MB / 192kB|
|Power Supply||5V USB or 5V from connector||6-16V or 5V USB|
|Debugger||On-board ST-Link||Standard ARM JTAG connector|
|USB Ports||1 OTG (micro AB)||2 OTG (mini AB)|
|User LEDs / Buttons||4 LEDs and 1 button||1 LED and 1 button|
|Other LEDs / Buttons||4 status LEDs, reset button||1 power LED, reset button|
Both boards have their own specific strengths being fitted with special features not present in the other one.
The Discovery board is apparently more oriented to showcase the Cortex-M4 DSP capabilities and its peripherals clearly show this. The Olimex STM32-E407 is more focused on communication capabilities and is a better platform for developing applications for the upcoming Internet of Things.
An important point about the STM32-E407 that is worth mentioning is that this board is open source hardware released under Creative Commons Attribution-Share Alike 3.0 United States License. I really like the openness aspect.
It would not be fun without a winner so let's go into details. Of course this comparison represents just my point of view, please feel free to contact me to address possible errors.
This is the hardest one, I own a dozen of different discovery kits and none of them had any defect however one of the three STM32F4-Discovery board I own had a partially unsoldered I/O connector, the board was still functional and I just re-soldered the connector but this is clearly a quality issue. I also own a dozen of different Olimex boards and I can't really complain about any of them. Also, my STM32-E407 is one of the two prototypes and it is still very good, no added wiring or other corrections.
Both boards have plenty available I/O pins but the Olimex board has an MCU with a huge LQFP144 package vs the LQFP100 found on the Discovery so it has a clear advantage in this area. Other strong points of the STM32-E407 are:
The STM32F4-Discovery can only be powered through the debug USB board or by providing 5 Volts through the I/O connectors, this is OK for a development board but not does not offer much flexibility. On the other hands the Olimex STM32-E407 mounts two efficient DC/DC converters and can be powered through a dedicated connector using any voltage from 6 to 16 volts DC, the power line is also protected by a robust 600 Watt Transient Voltage Suppressor (SMBJ16A) and filtered with a 470uF Capacitor. There is also the option to feed the board through OTG1, OTG2 or JTAG.
As mentioned before the two boards seem to target slightly different applications so a comparison cannot be done in this area.
LEDs and buttons are always useful for demos and debugging, the STM32F4-Discovery kit has more of them. Users at “my first flashing LED” level will appreciate this
The STM32F4-Discovery offers an on-board debugger implemented with an extra STM32, this is a huge bonus for a simple development board, the Olimex STM32-E407 is more oriented to “advanced” users who, most likely, already have a JTAG probe integrated with their “normal” development environment.
I think that the downward facing connectors on the STM32F4-Discovery board are annoying because they tend to scratch any surface I am using for work, also, I could want the connectors face upward, the Olimex STM32-E407 can mount rubber pads (included) and the connectors are not mounted.
The Olimex STM32-E407 has its two LEDs very close to its two small SMD buttons, I don't have a perfect sight and simply I don't see the buttons when the LEDs are lit, the STM32F4-Discovery has two nice and BIG buttons of different colors, I always know which is the reset one
Both boards are widely available but something that should be considered is that the Discovery kits are probably subsidized by ST and could no more be available when the STM32F4 will no more be the latest and the greatest, Olimex still stocks its old boards even those based on obsolete devices.
Last but not least the price. Both boards are really cheap, the STM32F4-Discovery can be found around 17€ from various distributors, the Olimex STM32-E407 is priced 39.95€ for a single unit but the price goes down for quantities.
The STM32F4-Discovery kits are cheap and great and I really love them, but this Olimex STM32-E407 is a really solid development board, it has almost everything done right.
Overall Winner: STM32-E407