The external expansion port (CATT, for “Connect All The Things”) on Tanmatsu has been designed to be compatible with both PMOD and SAO add-on boards, in addition to it being a port that exposes 8 GPIOs and 3.3v power it can also be used as JTAG interface for the ESP32-P4.
Pinout
| Pin | Function | CATT name | PMOD name | SAO name | JTAG name | GPIO | Description | Notes |
|---|---|---|---|---|---|---|---|---|
| 1 | Power out | +3.3v | - | +3.3v | +3.3v | - | 3.3v output | |
| 2 | Power out | GND | - | GND | GND | - | Ground | |
| 3 | GPIO | I2C SDA | IO8 | SDA | - | 12 | GPIO or I2C data | Used as I2C bus for automatic add-on detection |
| 4 | GPIO | I2C SCL | IO1 | SCL | - | 13 | GPIO or I2C clock | Used as I2C bus for automatic add-on detection |
| 5 | GPIO | USER A | IO7 | IO1 | - | 15 | GPIO | |
| 6 | GPIO | USER B | IO2 | IO2 | DETECT | 34 | GPIO, with special function | Pull low on startup to switch to JTAG mode |
| 7 | GPIO | USER C | IO6 | - | MTMS | 4 | GPIO or JTAG | |
| 8 | GPIO | USER D | IO3 | - | MTDO | 5 | GPIO or JTAG | |
| 9 | GPIO | USER E | IO5 | - | MTCK | 2 | GPIO or JTAG | |
| 10 | GPIO | USER F | IO4 | - | MTDI | 3 | GPIO or JTAG | |
| 11 | Power out | GND | GND | - | GND | - | Ground | |
| 12 | Power out | GND | GND | - | GND | - | Ground | |
| 13 | System reset | P4 reset | “3.3v” | - | P4 reset | - | Reset input for the ESP32-P4 | Can be converted to +3.3v output by shorting JP1 on the mainboard |
| 14 | Power out | +3.3v | - | +3.3v | - | 3.3v output |
Limitations, warnings and hints
- Total for all 3.3v outputs must not exceed 1A of current. It is generally adviced to stay well below this figure.
- Detect pin has a pull-up resistor connected, pull low to enable JTAG functionality for the ESP32-P4
- You can short jumper JP1 to connect pin 13 to the +3.3v rail
- Even if JTAG functioality is selected you can simply initialize a pin as GPIO to use it as such
- If you want to use JTAG via the USB-C port you will need to set the JTAG source manually in software if pin 6 (GPIO34) is being pulled low by an add-on board
