Some simple STM32 programs to explore analog output via the Microchip MCP4822 dual 12-bit DAC.
The programs are in C and may be compiled with 'arm-none-eabi-gcc' on Linux. They generate ELF and BIN output files which are suitable to program into STM32 chips for testing purposes.
The 'Makefile' also has targets for the STM32 programming tool 'stlink'.
At present, there's only support for the STM32F411 on the Black Pill development board. The main reason for this choice of chip is that I have dev boards for those chips that I can use for testing. Also, the STM32F411 has a hardware floating-point unit (FPU) which may prove to be useful for these programs.
The programs have been compiled, linked and tested using a Linux version of the 'arm-none-eabi-gcc' toolchain. This can be installed directly or as part of the Arduino IDE.
The compiler, linker, and programmers are invoked from the Makefile in the usual way. Various parameters in the Makefile may be altered to suit the development setup, e.g. the type of programmers used and the ports that they connect to. The full pathname to the toolchain is also configured in the Makefile.
Special targets in the Makefile are provided to invoke the programming device(s) and write the BIN files into the Flash memory in the chips. These targets are called 'prog' and 'progdds'.
There's a Makefile target called 'clean' that deletes the object code files and the ELF and BIN binary files. It leaves the source code files untouched, of course.
I have tested the code with an 'ST-LINK V2' programmer.
Blinking LEDs, of course! The LED should blink at 1Hz (500ms on, 500ms off). This frequency may be measured as a means of verifying correct clocking of the STM32 chip.
On the STM32F411, a 500Hz square wave should be generated on pin PC14. There's also a scope sync or trigger pulse on PB12 that is in phase with the signal generated by the DDS.
PC13 is the 1Hz LED.
Analog signals are read via ADC1 on ADC1_IN1 and ADC1_IN8. More ADC inputs to be added later.
The serial port(s) should transmit a message at 9600 baud.
Serial input is accepted on UART0.
To select different waveforms, the chips accept 's' for a sinewave, 'q' for a squarewave, 't' for a triangle wave, and 'w' for a sawtooth. This may change to become voltage-controlled in a future version.
- Implement external op-amp connected to MCP4822
- Implement active low-pass filter on MCP4822 output
- Make waveform selection voltage-controlled
- Add more waveforms
- Store waveforms in Flash memory
- Add more control voltage (CV) analog inputs
- Test with other ARM chips (e.g. STM32F103 on Blue Pill)