Simple STM32 based USB to DMX512 Interface
A simple and compact USB to DMX512 interface based on the STM32F042F6 microcontroller (20 pin TSSOP) is presented. The main intention for this project was to check out the DMX capabilities of STM32 microcontrollers.
DMX commands and power supply are provided via USB. It is seen by a host PC as a MIDI interface or as a virtual COM port.
Assembly of the simple STM32 USB to DMX interface (top and solder side view). Compact board size 43x30mm.
The USB interface is "full speed USB2.0" grade. The host sided USB class selection between MIDI and virtual COM port is made by a jumper on the SWD connector (may be extended to a switch). The 5V supply (total current no DMX load ca. 20 mA, with terminated DMX bus up to 50 mA) is scaled down by a linear low drop regulator to 3.3V which supplies the microcontroller.
In MIDI as well as in ASCII mode,
When USB works as virtual COM port, a special setup mode is available to configure the basic MIDI channel and user specific USB Vid/Pid. The user setup is stored nonvolatile in the microcontroller flash.
Because no RS-232 interface is installed on the board, the board is programmed (and debugged) via SWD ("Serial-Wire Debug") interface, preferably with ST-LINK, which is connected to the 3 pin socket next to the USB connector.
The firmware was developed with EmBitz 1.11. This source code is quite well suitable as a template for further own development, especially concerning DMX and USB. It is programmed directly on register level, no external libraries or drivers are used.
PCB layout for the STM32-UsbDmx board (1:1 TIF format, mirrored view "from component side" for PCB reproduction)
Firmware "stm32-usbdmx13.hex" for the STM32-UsbDmx interface (Version 1.3 , 13 October 2017)
Source code "stm32-usbdmx13.zip" for the STM32-UsbDmx board (status 13 October 2017)
* State of information October 2017.
* Right of technical modifications reserved. Provided 'as is' - without any warranty. Any responsibility is excluded.
* This description is for information only. No product specifications are assured in juridical sense.
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