Figure 9 display the highlighted 9 pin connector J303 on bottom side of SoM_IoT_2V0 printed circuit board. This connector allocate the large-scale integrated circuit R-IN32M3-EC with external I2C and two additional UART signals.
Pin 28 (I2C_SDA1)
Pin 29 (I2C_SCL1)
Pin 30 (UART_RXD0)
Pin 31 (UART_TXD0)
Pin 32 (UART_RTS0)
Pin 33 (GND) Ground
Pin 34 (UART_RXD1)
Pin 35 (UART_TXD1)
Pin 36 (UART_RTS1)