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CForth with STM32F042 Nucleo32 on support PCB

An early predecessor of this project was designed with a more conventional ASCII and MIDI based command set without possibility to create some kind of time-based action flow.
For better DIY reproduction, a very similar version with STM32F042 on TSSOP20 breakout board plus Veroboard support PCB design was developed.

Firmware exists for the conventional command set as well as for CForth. CForth with STM32F042 is much easier applicable for complex user specific projects and allows timeline-based user functions with program flow automatically modified by sensor input, e.g.

The intention to provide additionally a STM32 Nucleo-F042K6 support board is to make DIY furter more easy, especially when only partial features - peripheral I/O or USB/USART data transfer - are needed.
The main terminal interface is USB-COMM via the built-in ST-Link.

Specific features of CForth on STM32F042 Nucleo support board:

the firmware is almost the same as standard CForth for F042. CPU clock=48MHz. Two User Projects are available. Commands: "0 LOAD", "1 LOAD", "2 LOAD", "0 SAVE", "1 SAVE", "2 SAVE". by default the HSI clock (CPU internal RC oscillator) is used. in case of instablility, the ST-Link crystal oscillator is used (HSE). For the "USART" firmware a male subD connector and a MIDI input is on the PCB. It also provides PWM1, PWM2 and SPI. by default CForth is loaded. If jumper J1 is set, module starts as USB Comm <-> RS232 interface. USART baudrate is 115200KBaud or the one stored together with CForth project#1. Three times sending "CTRL_T" (dec.20) from terminal switches immediately to CForth. CForth command "11 SPLIT" switches immediately into USB/RS232 mode. Back to Cforth: 3x "CTRL_T". CForth command "13 SPLIT" switches immediately into transparent USBComm <-> USART MIDI interface with MIDI baudrate. Data format is bidirectional 1:1 byte streaming, differing from "3 SPLIT". Back to Cforth: 3x "CTRL_T". If no external communication via USART is needed, "Motor" firmware is recommended. Additional kernel ops for DC and stepper motor are implemented and some support for direct CPU register access: REGR, REGW, BSET, BCLR, BTST. Jumper J1 is ignored then. PA12 is available for user I/O, but must be in H-state at power-on. Else AUTOEXE is ignored

Downloads:
The subsequently downloadable material is copyrighted (c)2020-25 by Wolfgang Schemmert.
Assembly of the devices, programming and use of the software is permitted for free by everybody for any purpose ("freeware"). For commercial use, restrictions of third-party software contributors (Segger GmbH, STM) must be respected.
All information is based on best knowledge, but "as is" and without any warranty. Any responsibility is excluded. Use for dangerous, life-threatening and medical applications is forbidden.

Firmware "CForth-F042Nucleo-HSI-USART.hex" for RS232 or MIDI I/O via Usart.
SysClock = 48MHz HSI (CPU internal RC oscillator)
(02 April 2025 - hardware and features updated)

Firmware "CForth-F042Nucleo-HSE-USART.hex" for RS232 or MIDI I/O via Usart.
SysClock = 48MHz HSE (derived from ST-Link crystal oscillator. Nucleo HW modification necessary)
(02 April 2025 - hardware and features updated)

Firmware "CForth-F042Nucleo-HSI-Motor.hex", with additional user I/O.
SysClock = 48MHz HSI (CPU internal RC oscillator)
(02 April 2025 - hardware and features updated)

Firmware "CForth-F042Nucleo-HSE-Motor.hex" with additional user I/O.
SysClock = 48MHz HSE (derived from ST-Link crystal oscillator. Nucleo HW modification necessary)
(02 April 2025 - hardware and features updated)

Source code "CForth-F042Nucleo-v2.zip"
(state 02 April 2025) This source code is provided as complete "Segger Embedded Studio" project (ZIP file, 509 kB).
Parts published by Segger GmbH are under license of Segger&|Rowley, parts published by STM are under license of STM, parts programmed by me are provided under GNU GPL3 license.)

Some hints for best configuration of STM32F042 Nucleo32:
At state of delivery, there is no connection between the 8 MHz clock provided by ST-Link (SB4). Then source code "HSI" must be burnt. Problems with RS232-communication are possible, but tests with several CPUs used here were uncritical. In case of problem (or for longtime use under rough conditions), connect SB4 with a dot of solder (it is not necessary to unsolder SB6) and burn "HSE" code.
At state of delivery, PA6 with PB6 and PA5 with PB7 are interconnected. This is not extremely critical, but one of these connected pins should always be kept as input. A better solution is to remove SB16 and SB18. If you don't have an SMD unsolder tool, this can be handled carefully with 2 small solder pens. Socket connector PB3 is internally connected with the User LED, not available for user I/O.

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