External add-on port

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


connector

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