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The uTerm2-S (micro Term2 Stand-alone) is an easy to build multi-emulation RS232 terminal using an ESP32-Wroom-32 module and the great FabGL library ( More, using an ESP32 gives the opportunity to use the uTerm2-S in a lot of different ways easily using the Arduino IDE with the ESP32 core.

These the main specs of uTerm2-S:


Hardware Overview

uTerm-S (micro-Term Stand-alone) is a legacy RS232 VT100-like terminal.

It is the stand-alone version of uTerm, the terminal board for the Z80-MBC2 (or V20-MBC).

uTerm-S has a VGA out and PS/2 keyboard connector, a RS232 port, a power supply and a “transparent” serial-USB port.

Here three uTerm-S in action during a crazy experiment of a VHDL Z80 computer running MP/M with 4 concurrent users/terminals using my custom HW:

The trasparent SER_USB port (J3)

The uTerm-S has a “transparent” USB-serial adapter connector, so you can upload firmware to the Z80-MBC2 (or V20-MBC) (using Arduino IDE) or load an Intel-Hex file (with iLoad) or use XMODEM to exchange files with a PC (running a terminal emulator that supports XMODEM file transfer) while the uTerm is in use.

Both the “mixed” power supply scenarios (USB-serial adapter not powered from USB but uTerm-S powered and vice-versa) are managed by the HW, so you don't need to worry about it.

In the following photo a serial-USB adapter is connected with a cable to the transparent SER_USB port:

This allows to use two keyboards and two monitors in the same time (one keyboard and monitor attached directly to the uTerm-S, and another keyboard and monitor of the terminal emulator on a PC connected with the serial-USB).

Or you can use the monitor attached to the uTerm-S and the keyboard of the terminal emulator on a PC.
Please note that the SER_USB port support both the RTS/CTS HW handshaking, so to use them both RTS/CTS signals are needed on the serial-USB adapter:

Changing the RS232 speed (J1)

It is possible choose among 3 baud rate (the most common ones) using a jumper on J1 (AUX) as shown in the following image:

Changing the color (JP2-JP3)

It is possible choose among 4 colors (green, white, cyan, amber) for the output VGA signal.
To select the color use the JP2 and JP3 jumpers.

Color RED (JP2) BLUE (JP3)
Amber X X=X X=X X
Blue X=X X X X=X
Green X=X X X=X X
White X X=X X X=X

In the following photos are shown the setting for JP2 and JP3 to select the color as white or green respectively:

The RTS-HS switch (SW2)

The RTS-HS switch is used to turn on or off the RTS handshaking.

When turned off, the host connected to the serial port will see the RST line always active. This can be handy in various situations.

If RTS-HS is always off you don't need to connect it on the serial-USB adapter.

The flashing procedure is the same of uTerm.
So refer to the same paragraph of the uTerm page taking into account that here the SWD connector is marked J3 instead of J6.

How to get a PCB

I've prepared an “easy link” to order a small lot (min. 5 pcs) of PCB here.

How to get a Kit or an Assembled unit

If you are looking for a kit with all the needed parts or an assembled unit ready to use there is a professional seller that can sell both and ship worldwide.

The link to the seller is this one.

Credits & License

The video terminal is based on the ChibiTerm by K. C. Lee.

VT100 emulation was added by Madis Kaal.

All the project files are licensed under GPL v3.



PCB Assembling Guide.

BOM file.

PCB Gerber files.

The firmware for the STM32 MCU in binary format ready to be flashed.
This new version solves a bug in some situations using the right CTRL key (i.e. CTRL-L).

Source files for Keil.

uterm2-s.txt · Last modified: 2022/09/05 21:53 by admin

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