I have made a small PCB with an STM32F4 microcontroller and a TI CC2520 radio transceiver. There are many mote modules available already, but I wanted one optimized for performance as opposed to power consumption. I also wanted to try making a PCB with some RF-parts since I haven’t done that before.
These are the 2-layer PCBs ordered from OSHPark:
This article will describe how to debug the STM32F4 microcontroller using the zylin eclipse plugin. The following setup will be used:
The result will look something like this:
You can:
I have not written any new post for a while, so here is one more project for the stm32f4 discovery. I prepared this post a long time ago, but for some reason I never posted it, so here goes:
Based on one of the examples provided by ST, I have written a program for the STM32F4 Discovery board that plays MP3 files from an USB memory stick. You can download it here.
If you use a usb-host cable such as this one you can connect an USB memory stick (with fat32 file system) with mp3-files to the micro-usb port of the stm32f4 discovery. The files should then be played one by one. The user button can be used to skip to the next file.
If you follow this tutorial you should be able to build and upload the provided files right away.
The main.c-file has many comments, so hopefully you can figure out how it works. Using a USB-memorystick for logging is quite easy with this program as a basis. Only the two usb-pins, 5V and gnd are required to connect it to any stm32 with USB support, so hw-wise it’s even easier than using an SD-card.
Based on this, I have written a small program for the STM32F4 Discovery that uses the USB-CDC class to show up as an virtual serial port. I’m using the USB stack provided by ST, however, there is also another project that uses libopencm3 that can be found here. I have routed the write system call to use this port, so the stdio printf function will print directly to this serial port.
If you don’t have the necessary toolchain to build and upload programs to the STM32F4, you can have a look at this post. Otherwise, the following steps should be sufficient:
The current program runs some floating point operations and prints the elapsed time on the USB-CDC serial port. The float parameters in the makefile can be changed to see how the FPU affects the speed (and there is a lot of difference). Remember to run clean after changing the float parameters, as the object files are not compatible between hardfloat and softfloat builds.
Update: I also have a project that plays mp3 from an USB memory stick with a fat32 file system here.
I have written a simple program for the STM32F4 Discovery board that plays a short mp3 file from flash memory. For the decoding, the fixed point version of the Helix mp3 decoder is used. The audio output driver is the one used for the Peridiummmm demo, modified to use the peripheral library provided by ST.
The audio driver has two DMA buffers and a callback function that asks a user-provided function to fill one buffer with audio data when it runs out, while the other DMA buffer is streamed to the audio CODEC. This user function decodes one MP3 frame and forwards the raw audio samples to the audio driver. As this is interrupt driven, the main function can still be used for other things.
If you don’t have the necessary toolchain to build and upload programs to the STM32F4, you can have a look at this post. Otherwise, the following steps should be enough to test it:
That’s it! It should be quite easy to modify the code to play mp3s from, for instance, an external SD card.
The the mp3_data[] in src/mp3_data.c is just the raw data of a normal mp3 file. I used this perl script to convert the mp3 file to a c array. After you unzip the perl script, you can use it like this:
chmod +x bin2hex ./bin2hex MP3FILE.mp3 1 > mp3_data.c |
Where MP3FILE.mp3 should be replaced with the mp3 file you want to convert.
Remember that the mp3 file has to be small enough to fit on flash memory of the STM32F4. You can use Audacity to trim/re-encode mp3 files. You should also clear the ID3 tag if possible, as this saves space. As it is now, stereo files with 44.1 KHz sample rate (and any bitrate, even VBR) can be played. When the number of channels or the sample rate differs, the playback speed will become incorrect. This can of course be fixed easily, but I wanted to keep this example as simple as possible.
On Ubuntu, you can install audacity with:
sudo apt-get install audacity |
Updated 2014-04-03
This tutorial describes how to set up a complete and free toolchain for STM32F4xx microcontrollers, including how to use hardware floating point support. It is mostly aimed towards beginners with ARM microcontrollers, however, experienced developers could probably find something useful here as well. It is assumed that the reader is a bit familiar with the C programming language and the Bash terminal.
At the end of this tutorial, the reader should be able to build and upload programs to the STM32F4** using the STLinkV2 interface (such as the one found on the STM32F4 Discovery board). This is done using Ubuntu Linux in this tutorial, however, the instructions should be general enough to make this work on any Debian-based GNU/Linux distribution.
The following hardware/software will be used: