Uno R4 WiFi - JST header no SDA or SCL

Official Hardware UNO Family UNO R4 WiFi
1

Just got a Uno R4 and trying to use the small JST header. The 3.3v and ground postions are intact to the board but the last 2 pins for SDA and SCL are not connected to any pin of the PCB. Did I just get a bad Uno R4? It's authentic Uno R4 not clone.

2

How did you determine that?

3

The JST connector is for the Wire1 I2C bus, SCL and SDA only connect to the processor itself connect to the processor through level translators Q1 and Q2. The A4/SDA A5/SCL Wire bus is completely separate.

Note, the UNO R4 has no JST connector, that is only on the UNO R4 WiFi.

4

I updated the title, I meant the Uno R4 Wifi.

5

The full advanced pinout of the R4 WiFi accurately shows the SDA/SCL pins and none are on the SPI or even the ESP32 header...

ABX00087-full-pinout_Page_4
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You can find IIC SDA1/SCL1 (Wire) on A4/A5 or D18/D9, IIC0 SDA/SCL (Wire1) on the QWIIC connector, and SCI (Simple IIC) SDA2/SCL2 (Wire2) on D1/D0.

They all work, just note that because Wire2 is SCI it can only be an I2C bus controller and you need to use TwoWire (or equivalent) to start it...

#include <Wire.h>

int sda_pin = 1;
int scl_pin = 0;
TwoWire Wire2(scl_pin, sda_pin, ADDRESS_MODE_7_BITS, true);

void setup() {
  Wire2.begin();
}