back to menue

CForth is a simple 32bit Forth interpreter system completely written in C language.
(no relationship to "Mitch Bradley's CForth")
The intention is to provide a straightforward user oriented Forth system,
specifically to organize interactive electronic control of art objects and installations or similar process control.

Primarily CForth was developed for the 32pin LQFP STM32G431KB and STM32G441KB processor.
I am a fan of these compact, high featured and easy to solder chips. Though originally bought for another project, the lockout time stimulated me to start this Forth development. My first Forth about 1992 was e-Forth with an 80C31 processor. Later I programmed some Forth for 68HC11 and AT90/ATmega. My last Forth interest was early 2000 a Windows console version written in C, which served as a first template for the actual project.
 
Because it is complicated to etch PCBs without appropriate tools, a Veroboard compatible PCB layout was developed (processor soldered on DIL breakout board like Adafruit 1163), which is presented here.
 
Very new is a LQFP48 version for STM32G4xx processors. It is a simplified "Black Pill" compatible PCB layout. Because it is made with home-makers technologies, the USB connector, the reset button and the BOOT0 button could not be integrated on the PCB. Therefore it is called "Grey Pill".
 
All firmware versions include a combined RS-232/MIDI interface, an SPI interface, two PWM pulse outputs, an I2C interface and a random number generator.
Furthermore, an optional DMX512 output for the Veroboard PCB version is added.
All of these features are accessed directly with specialized CForth kernel operators (Forth "words").
 
A reduced version for an unmodified STM32G431 Nucleo-64 is available, too
But I am very disappointed about this Nucleo, it is an absolute downgrade of the Nucleo concept. Because the ST-LINK unit cannot be cut off and be used as a standalone programmer, it's effectively a playaround gadget and not useful for real projects. If I had known before, I would not have ordered it. Because the firmware modification for this board is quite easy, it is supported too with basic features.
 
Soon after, firmware and Veroboard compatible PCB layouts for 20pin TSSOP STM32F042F6 and 32 pin LQFP STM32F042K6 were developed. Also works with STM32F070.
The small memory size (Flash as well as SRAM) of these processors demands some restrictions concerning number of kernel operators, max. size of user programs, available I/O features.
To open this bottleneck a little bit, the threaded code for these processors is organized in a compact 8 bit array. This provides up to 3 times more Forth code compared with a straight 32bit word oriented code thread (which is used for the STM32G4 processors). The additional runtime overhead is moderate.
 
Veroboard compatible PCB designs:

CForth has been ported to other STM32 projects and processors. These projects are described on individual HTML pages:

• CForth for STM32F411 Black Pill and for Nucleo-64 (STM32L476 or STM32F411) with ST-LINK cut off.
  This firmware has essentially the same features as the standard STM32G431 version.
  Firmware versions for unmodified Nucleo boards are provided, too.
• An experimental small STM32G431 CForth based USB/DMX512 controller
• A slightly modified CForth firmware is designed for the STM32F042 small USB to Midi or RS-232 interface. Corresponding firmware "CForth-F042-mini.hex" is provided below. The actual firmware version (April2024) allows to configure the board by jumper into a USB to USART RS232 interface or into a USB to USART MIDI interface. Details see Operating Manual p.15.
• Low power versions for STM32G4xx, STM32F042, STM32F030 and STM32L031. These versions operate with very low CPU clock frequency and are intended to be supplied by small solar panels or other energy harvesting arrangements.

Most essential features of the CForth kernel:

• A basic set of standard Forth kernel operators ("words") is implemented
• No attempt is made to comply with established Forth standards. Nevertheless, all typical user application oriented features of most Forth dialects are supported.
• No attempt is made to "program Forth by Forth". At the expensive of code length everything is programmed on quite flat subroutine nesting.
• Where standard Forth systems compile sniblets of assembler code to manage runtime behaviour,
  specific "doAll" runtime operators are introduced for loops, conditionals, VARCONs. So I think, I have got an acceptably fast and rather easy to understand and to manage Forth system.
• VARCON ("valiable constant") is a new data type which combines the features of variables and constants. Conventional Forth word '@' is not necessary and '!' is replaced by REV. This takes some more time during compilation, but saves code execution runtime.
• Loops are organized more "C-programming style" than in traditional Forth.
• A simple background process for debugging and parameter optimization is implemented: selected CForth kernel operators can be called via terminal while another CForth thread is executing.
  This way VARCONs of the main thread can be modified externally during runtime for example, which allows interactive flow control of the executing thread.
  Single step execution can be switched on and off at any time and some debug information (like memory content) can be displayed via terminal during runtime of the main thread. The background process can be switched off, to get approx. 40% higher execution speed.
• Any CForth User thread can be replaced by a new programmed one without "ripping" up the compiled code memory and complile it new (kernel operators REPLACE and RESTORE). Changes can be undone interactively without reprogramming. This may be useful when a good idea comes later or to remove or insert debug features without reprogramming all.
• Direct access to CPU internal peripheral registers is possible with kernel operators REGW and REGR.
• Line-end delimiter is "Carriage Return" (ASCII 13) only. To modify it into "Line Feed" (ASCII 10), exchange the numeric values of CRR and LFF in source file "globaldefines.h" and recompile.
• Some firmware versions and hardware designs for STM32G431 support CForth based DMX512 control in addition to digital and analog I/O.

A detailled CForth Operating Manual (PDF file), and
A hardware DIY Construction Manual for STM32G431/G441 and STM32F042 (HTML file) is provided here.

A good tool for Forth source code upload is my DTerm Windows terminal software. It is surely not the best terminal emulator, but has been developed over the years for best fitness with my actual projects.

Downloads:
The subsequently downloadable material is copyrighted (c)2020-24 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.

The actual firmware is programmed with "Segger Embedded Studio 5.44".

Firmware "CForth-G4xx-48.hex" for Veroboard compatible PCB, LQFP32, SysClock = 48MHz
(09 April 2024 - bugfix)

Firmware "CForth-G4xx-144.hex" for Veroboard compatible PCB, LQFP32, SysClock = 144MHz
(09 April 2024 - bugfix)

Firmware "CForth-G4xx-DMX48.hex"
with a set of DMX512 kernel operators for Veroboard compatible PCB, LQFP32, SysClock = 48MHz
(09 April 2024 - bugfix)

Firmware "CForth-G4xx-DMX144.hex"
with a set of DMX512 kernel operators for Veroboard compatible PCB, LQFP32, SysClock = 144MHz
(09 April 2024 - bugfix)

Firmware "CForth-G4xx-Grey48" (LQFP48 "Grey Pill")
for Black Pill compatible Veroboard PCB, LQFP48, SysClock = 48MHz
(09 April 2024 - bugfix)

Firmware "CForth-G4xx-Grey144.hex" (LQFP48 "Grey Pill")
for Black Pill compatible Veroboard PCB, LQFP48, SysClock = 144MHz
(09 April 2024 - bugfix)

Firmware "CForth-G4xx-GreyDMX48.hex" (LQFP48 "Grey Pill")
with a set of DMX512 kernel operators for Black Pill compatible Veroboard PCB, LQFP48, SysClock = 48MHz
(09 April 2024 - bugfix)

Firmware "CForth-G4xx-GreyDMX144.hex" (LQFP48 "Grey Pill")
with a set of DMX512 kernel operators for Black Pill compatible Veroboard PCB, LQFP48, SysClock = 144MHz
(09 April 2024 - bugfix)

Source code "CForth-G4xx-v62.zip"
(state 10 April 2024) This source code is provided as complete "Segger Embedded Studio" project (ZIP file, 1036 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.

Firmware "CForth-F042-pwm2.hex" for 20pin TSSOP Veroboard compatible PCB, SysClock = 48MHz.
Kernel Ops for SPI and PWM1,PWM2 included. USART can operate as terminal or as serial I/O
(09 April 2024 - minor improvements and bugfix)

Firmware "CForth-F042LQFP-pwm2.hex" for 32pin LQFP Veroboard compatible PCB, SysClock = 48MHz.
Kernel Ops for SPI and PWM1,PWM2 included. USART can operate as terminal or as serial I/O
(09 April 2024 - minor improvements and bugfix)

Firmware "CForth-F042-motor.hex" for 20pin TSSOP Veroboard compatible PCB, SysClock = 48MHz.
Kernel Ops for SPI, stepper motor and PWM1 included. PWM2 not implemented. USART can operate as terminal or as serial I/O
(09 April 2024 - minor improvements and bugfix)

Firmware "CForth-F042LQFP-motor.hex" for 32pin LQFP Veroboard compatible PCB, SysClock = 48MHz.
Kernel Ops for SPI, stepper motor and PWM1 included. PWM2 not implemented. USART can operate as terminal or as serial I/O
(09 April 2024 - minor improvements and bugfix)

Firmware "CForth-F042-midi.hex" can operate the serial I/O as conventional RS-232 or as MIDI interface.
By jumper, this board can be started as a USB-to USART RS232 interface or into a USB-to conventional USART MIDI interface. Details see CForth Operating Manual p.15.
Instead no SPI, motor and PWM code implemented. For 20pin TSSOP Veroboard compatible PCB, SysClock = 48MHz
(09 April 2024 - improvements and bugfix)

Firmware "CForth-F042LQFP-midi.hex" can operate the serial I/O as conventional RS-232 or as MIDI interface.
Instead no SPI, motor and PWM code implemented. For 32pin LQFP Veroboard compatible PCB, SysClock = 48MHz
(09 April 2024 - minor improvements and bugfix)

Firmware "CForth-F042-mini.hex" This firmware fits for the small USB/serial interface, the USART Tx level is not inverted, because this board is equipped with an external CMOS inverter and 5V level shifter.
Else this code is the same as "CForth-F042-midi.hex". SysClock = 48MHz.
By jumper, this board can be started as a USB-to USART RS232 interface or into a USB-to conventional USART MIDI interface. Details see CForth Operating Manual p.15.
(09 April 2024 - improvements and bugfix)

Source code "CForth-F042-v37.zip"
(09 April 2024) This source code is provided as complete "Segger Embedded Studio" project (ZIP file, 512 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.

Firmware "CForth-NucleoG431-48.hex", SysClock = 48MHz
reduced version for an unmodified STM32 Nucleo G431 board
(09 April 2024 - bugfix)

Firmware "CForth-NucleoG431-144.hex", SysClock = 144MHz
reduced version for an unmodified STM32 Nucleo G431 board.
Terminal communication exclusively via ST-Link USB.
(09 April 2024 - bugfix)

Source code "CForth-NucleoG431-v19.zip"
(state 09 April 2024) This source code is provided as complete "Segger Embedded Studio" project (ZIP file, 434 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.

These projects are programmed directly on register level, no external libraries (except "cmsis", startup code and Segger system code), no external drivers or HAL are used.

back to menue