ST Micro-electronics Device Firmware Upgrade (DFU/DfuSe) from C#

• Download example source code - 29.2 KB

Introduction

ST Micro-electronics STM32F series micro-controllers have the possibility to be programmed via USB using ST's DFU protocol. Some of their micros have the DFU module in ROM and all can have it in FLASH. DFU is a very handy way to program a micro-controller, particularly when it is in the micro's ROM, but all the example code from ST is in C++ and is somewhat complicated and buggy. ST's version of DFU is called DfuSe (Device firmware upgrade STMicroelectronics Extension).

Using this code, I have been able to implement a scheme whereby the C# application which is communicating with the ST micro-controller based hardware, is able to automatically update the hardware's firmware. So when the C# application is updated, the firmware gets updated too.

Background

ST provides a C++ demo application, which includes the Windows drivers for the DFU device and two DLLs which this application requires (STDFU.dll, STTubeDevice30.dll). I'm not sure of the redistribution terms of the DLLs so you should download them directly from ST by downloading and installing ST's demo package (see below). Then copy the two DLLs into the main solution directory, from where they will be copied into the appropriate bin directory when the solution is built.

• ST's demo installation package also contains some useful documentation
• ST also provides a protocol description (AN3156) here 

ST provides a STDFU library specification (UM0384) and file format document (UM0391) as part of the demo package.

Some of the USB communications has been borrowed from an excellent article on USB HID programming that I found here.

ST's application uses another two DLLs, STDFUFiles.dll and STDFUPRT.dll. These perform higher level functions which are either not performed by my example, or done by the C#. I just wanted to write as much of the code in C# as possible, and minimise time spent trying to decode DLL function calls. I also haven't bothered to implement any more functionality than the bare minimum I needed, but I hope this will provide a starting point for people wanting to do more.

DFU files can be generated from HEX or S19 files by an application which is included in ST's demo package. So you can take the HEX file output from your compiler (e.g., Keil's MDK-ARM) and convert it into a DFU file which can then be programmed into a micro-controller using this application. Normally, this is something you would do with released code, rather than during software development. Using the DFU avoids the need for the production department or service engineer to have a JTAG programmer, and the need to directly access the target hardware as long as the USB port is accessible.

Using the Code

The supplied code is a demo application plus my FirmwareUpdate class which does the hard work of communicating with the hardware. My intention is more that it provides an example of how to implement DFU programming in your own test harness than that it be used standalone. I don't claim to be an expert in USB or P/Invoke, what I am presenting has been patched together by running the C++ demo under a debugger and experimentation.

IFirmwareUpdate is of course an interface class to the FirmwareUpdate class. To do a firmware update, first hook the OnFirmwareUpdateProgress event to an event handler, then call UpdateFirmware with the path of the DFU file. You make like to use ParseDFU_File beforehand to obtain the intended VID and PID of the DFU file so you can check that they are correct for the target hardware.

This code has been tested against a STM32F207's ROM bootloader, a STM32F103 running a FLASH DFU module (as copied from ST's example) in the bottom $3000 bytes to load an application into the FLASH from $08003000 onwards, and another STM32F103 running a slightly different version of ST's DFU example. I have built the project both "x86" and "x64". You will need to install the correct version of the DFU driver, as supplied in the form of an installer EXE file in ST's demo package.

You may notice a function called FindAndDetachHID. This is for use with a HID device (Human Interface Device, such as keyboard or joystick, but also one of the easiest USB classes to use for any kind of low data rate I/O device) which supports the "HID detach" feature. This is basically a special message telling the device to stop being whatever it is, disconnect from the computer, and then re-connect as a DFU device. ST's demo app supports this feature.

History

• 19/2/2013: First posted.