Primarily CForth was developed for a 32pin LQFP STM32G431KB processor, a compatible hardware design is described here. In CForth context, STM32G441 processors are 100% compatible with STM32G431. For this reason only STM32G431 is used for both below.
From this basic version, a small CForth based USB/DMX controller board with STM32G431KB was derived and finally a simplified "Black Pill" pinout compatible version for STM32G4xx LQFP48 case (called "Grey Pill").
 
Additionally firmware for 20pin TSSOP STM32F042F6 and 32pin LQFP STM32F042K6 was developed and a compatible hardware proposal is described. Works with STM32F070, too.
 
Because it is complicated to etch PCBs without appropriate tools, Veroboard compatible PCB layouts are presented here. Because such a layout is quite coarse, also etching is possible with simple equipment.
 
The actual hardware USART Tx output is designed without external inverter/driver, the idle low level is obtained by inversion at USART register level. For this reason, the TxD "logical 0" level is only 3.3Volt, a 100 Ohm resistor is added as short circuit protection. This has been tested with several third party RS-232 inputs, which typically have a trigger level around 0.7 Volt and an input impedance in the order of 5kOhm.
Somewhat more critical is the use of this Tx driver as MIDI OUT. With a modified connector wiring (see below) commonly used MIDI interfaces are safely driven with 5mA or more.

Hardware for STM32G431KB
Old versions (<7.55) have partially different I/O connections

Veroboard layout after some redesign.
 

Small USB/DMX controller with STM32G431KB

Hardware for STM32F042F6 (20pin TSSOP) (works with STM32F070F6, too)

Hardware for STM32F042K6 (32pin LQFP) (works with STM32F070K6, too)

Hardware for STM32G4xx (48pin LQFP) "Black Pill" compatible pinout ("Grey Pill")
 
This PCB is intended for easy support of a "Black Pill" standalone module with some practically useful peripherals. Specifically it may be assembled (or not) with a combined RS-232/MIDI interface and a DMX512 lighting control transmitter plus some area for user specific completion.
 
My "Grey Pill" design is a simplified Black Pill pin compatible PCB for LQFP48 STM32G4xx processors. It does not have the USB connector, Reset button and BOOT0 button onboard. So this PCB is needed for practical use of the "Grey Pill" module.

Because STM32F411 does not support inverted USART TX output, an external inverter IC3 is provided. Though it is a very tiny chip, it fits into the Veroboard raster.
"Grey Pill" and original Black Pill have assigned the DMX transmitter at different processor ports. For this reason, the appropriate resistor R7* or R7** must be connected via solder bridge.

Additional hardware for Stepper and DC Motor control
The actual firmware supports control of stepper motors (kernel ops MOT1, MOT2, MOT3).
To save I/O pins, a simple converter circuit is proposed to convert a two line phase step sequence into a four line sequence to be used for unipolar stepper motors:

For connection with TB6612 dual H bridge driver (Adafruit breakout board recommended), the four 74HC02 outputs are connected with corresponding TB6612 pins. PWM A,B pins are connected with corresponding PWM I/O pin. This way, the speed of commutated DC motors can be regulated.   For stepper motors, the PWM must be set at maximum level. High Stop level sets all motor outputs to high impedance, 0 PWM sets all outputs to LOW.

Hints for Veroboard assembly
It is useful to print a mirrored version of the placement drawing to get a view from bottom=solder side.
The diameter of the wire should be 0.5 or 0.4 mm for easy bending and diagonal wiring between the neighboured copper dots. A set of "adjustment" pliers with small flat tips (or stable tweezers) is recommended for bending and positioning the wires. For 45 degree bendings, a small screw driver pressed on the wire is helpful.
 
The correct positioning of parts is essential, because there is almost no reserve for alternative positioning. The final solder process is less complicated than it looks. So it is recommended first to place all parts (bigger and typical parts first) and solder them as slightly as possible only to fix them provisionally. Next cut longer wires of fixed components about 1 mm above the Veroboard for later final soldering. At this stage, parts with more than two contacts like connectors should be soldered only at 2 diagonal edge pins. Try to organize the solder sequence in a way that one alreay soldered point is connected with another yet unsoldered, if possible. Points wit 2.5 mm distance are not soldered with a wire, but with a dot of solder instead. If you are connecting points with 3.6 or 5mm distance, becareful not to unsolder the already soldered point due to much heat on the wire.
 
In some cases jumper wires must be placed before IC sockets. Length and position of all wires (except USB data lines) is uncritical. So if something goes wrong, forgotten or non-placeable wires can be put later directly with isolated wire.

MIDI OUT with 3.3 V "logic0" level: