ESP32TNC is a Terminal Node Controller (TNC) that is implemented for Espressif ESP32 processor.

feature

• supported hardware: FX.25 KISS TNC rev.1/2/3/4 and M5Atom, M5StickC Plus
• using small interface board (ESP32TNC HAT) connecting to a transceiver
• using ESP-IDF development framework to install TNC software
• support Bell202 1200bps AFSK
• implementing software modem, decoding capability same as TI TCM3105 modem chip
  • about 980 packets can be decoded against WA8LMF TNC TEST CD Track 1
• support FX.25 forward error correction (Direwolf compatible)
• support KISS protocol only
• using USB serial for host connection and power supply
• support Wi-Fi connection (TCP and UDP)
• display received packet on the LCD (M5StickC Plus only)
• working with internal battery (M5StickC Plus only)
• decoding packet sound without TNC HAT using internal MIC (M5StickC Plus only)

Caution: not supported normal M5StickC

ESP32TNC HAT is small interface board for connecting to a transceiver.

• size is 24x24mm (same as footprint of M5Atom)
• same PCB can support both M5Atom and M5StickC Plus
• small number of parts (1 transistor, 5 resistors, 3 capacitors, etc.)
• smallest TNC HAT in the world, may be :)

The schematic is here. (for KiCAD)
The gerber data is here. (for Seeed Fusion PCB)

R4 and D3 are missing number.
J1/J2 or J6 is alternative.

Solder jumper is needed depending on a transceiver.

for Standard/Icom/Yaesu

for Kenwood

• install ESP-IDF, ESP-IDF v4.2 is needed
• download TNC software

git clone https://github.com/amedes/ESP32TNC.git

• configure TNC software

idf.py menuconfig

• chose ether M5StickC Plus or M5Atom
  
• compile and install

idf.py -p PORT -b 1500000 flash monitor

(To exit the serial monitor, type Ctrl-].)

• have fun!

• ESP32TNC will hang up when a packet radio application opens the USB com port.

The auto-download circuit of M5Atom/M5StickC Plus is wrong. So opening of the USB com port may reset the ESP32TNC and keep the reset state depending on the com port driver behavior. There is no workaround to avoid this fault. The following procedure may help you.

1. unplug the ESP32TNC from the computer
2. plug the ESP32TNC to the computer again and pray for luck
3. re-execute the packet radio application
4. repeat above procedure until good luck becomes...