Figure 10 display the highlighted 9 pin connector J301 on bottom side of SoM_IoT_2V0 printed circuit board. With connector J301 are two 10BASE-T, 100BASE-TX/FX ethernet ports realized. The SoM-iRJ45 module includes the R-IN32M3-EC Ethernet Switch with additional TVS array connection for ESD and transient protection. Furthermore, the magnetic components for galvanic decoupling and signal integrity are offered too. See description below on this page.
Pin 37 (RX0_N) connect the differential receiver_N signal of ethernet port 0 and transfer this signal to target device.
Pin 38 (RX0_P) connect the differential receiver_P signal of ethernet port 0 and transfer this signal to target device.
Pin 39 (TX0_N) connect the differential transceiver_N signal of ethernet port 0 and transfer this signal to target device.
Pin 40 (TX0_P) connect the differential transceiver_P signal of ethernet port 0 and transfer this signal to target device.
Pin 41 (SHIELD) connect the external Ethernet-Shield for both ethernet ports.
Pin 42 (RX1_N) connect the differential receiver_N signal of ethernet port 1 and transfer this signal to target device.
Pin 43 (RX1_P) connect the differential receiver_P signal of ethernet port 1 and transfer this signal to target device.
Pin 44 (TX1_N) connect the differential transceiver_N signal of ethernet port 1 and transfer this signal to target device.
Pin 45 (TX1_P) connect the differential transceiver_P signal of ethernet port 1 and transfer this signal to target device.
Exemplary magnetic topology
Following Schematic 2 pictured the used HX1188 magnetic circuit topology. Two of this component are on module PCB for both ethernet port integrated. The transmit part of HX1188 decouple both differential transmit signals (TxP/ TxN) for one ethernet port between MCU and RJ45 connector contacts. Equal to receive part of HX1188 for both differential receive signals (RxP/ RxN).
Following Schematic 4 show the wiring concept of ethernet port 0 between MCU (R-IN32M3-EC) and Ethernet jack connection contacts. A consistent differential signal cabling is recommended.
All components on left side of blue marked J301 connector are equipped on SoM_iRJ45 module. The schematically pictured RJ45 connector has to be placed on target device and is not part of SoM module.
Note: It is recommended the open pins of the external Ethernet connectors on carrier board, for RJ45 Jacks the pin 4/5 and 7/8, to decouple with 75Ω resistors and 1MΩ resistor to shield potential.
Ethernet Shield Connection
The Ethernet shielding connection for the external cabling shield has to be connected at J301 pin 41. Which is pictured in Schematic 3. This potential (J301_Pin41) is recommended to connect with functional earth in the local operating environment. This ensures an interference deflection and protect the module method of operating.
Note: Do not connect J301 pin 41 with GND, otherwise all cable interspersed disturbances will have negative influence to module circuit. This SHIELD is internal decoupled with resistor/capacitor network to system GND!