The Ethernet to SPI interface iMOD module has a RJ45 connector with built-in magnetics, LEDs and PoE (Power over Ethernet) circuitry. This module has press-fit connectors for easy integration onto a target board, with no soldering required. It can be mounted on a custom board, a prototype board, or boards with a 0.9" iMod port.
The RJ45 connector allows power to be obtained via the network cable from either the two used pairs (pins 1,2,3 and 6), or the two unused pairs (4,5,7 and 8), as defined by the PoE standard. A provision is also made for a custom, cheaper implementation of PoE by routing power from the unused network pairs (4,5,7 and 8) via a diode to the Auxiliary power pin of the module. This auxiliary power can be used to power the target board.
This Ethernet-to-SPI interface iMod module uses Microchip's ENC28J60 Ethernet controller.
The module has two rows of press-fit connectors on the bottom of the board. They can be pressed into 1.00mm holes on a 1.6mm thick (standard PCB thickness) target board. No special tool is required; they can be inserted by applying firm pressure to the connectors. Once fitted to the target board, the board is very secure, and can not be removed by hand. A screwdriver or similar tool can be used to remove the board if required.
If the module is to be soldered onto the target board, 1.10mm holes can be used. This will allow it to be inserted much easier than with 1.00mm holes. When using 1.10mm holes, the board can be removed by hand if left unsoldered.
Ethernet-to-SPI Add-on Module Features
- IEEE 802.3 compatible Ethernet controller
- Integrated MAC and 10BASE-T PHY
- SPI interface with clock speeds up to 20 MHz
- 8-Kbyte transmit/receive packet dual port SRAM
- Two programmable LEDs for LINK, TX, RX, collision and full/half-duplex status
- Power-over-Ethernet (PoE) circuitry for extracting power via used or unused cable pairs
- Press-fit connectors are gold plated for best possible contact
- High-quality assembly and components
- Module dimensions: 27mm × 26.5mm (1.065" × 1.045")
- RoHS compliant
- Operating temperature: -20°C to +70°C
iMod Pin Configuration This is an iMod module with 0.9" pin column width, meaning it uses a standard pinout and configuration that allows it to be connected easily to any host board that has a 0.9" wide iMod port (some iMod ports may only support 0.7" width). This includes the Modtronix SBC83I and the various PT66E Prototyping Add-ons for boards in the SBC66 series.
The pin pitch is 0.1" so you can use the module also on any typical prototyping board or breadboard.
For information about the iMod pinout, download this iMod Overview. Find other iMod modules in our iMod Category.
Power over Ethernet
Official IEEE 802.3af PoE Implementation
The official IEEE 802.3af Power over Ethernet standard provides 48V DC over two of the four available pairs of the network cable with a maximum current of 400mA, for a maximum load power of 15.4W. The circuit required to convert this to 5V or 3.3V is quite complex and expensive. It is not implemented by this module! All four signals — POE+1, POE-1, POE+2 and POE-2 — are required to implement IEEE 802.3af. This is because the PSE (Power Sourcing Equipment, like a switch that provides PoE for example) can provide power on either POE-1 and POE+2, or POE-2 and POE+2 according to the standard. The X1U and X2U connectors have to be assembled to get access to these signals. They are not assembled by default, as can be seen in picture to the right — the upper two pins on each side.
Proprietary PoE Implementation
A cheap and simple alternative to the official IEEE 802.3af implementation is to use the spare pairs of the network cable (pins 4,5,7 and 8 of network connector) for power. There are many commercial products available that use this method. An injector is required to put the power (normally 12V or 24V) on the network cable. This injector is located normally at the switch, and will place power on all cables that require it. The PD (powered devices) on the other end of the cable can then use this module to access the supply voltage on the network cable.
The figure below shows the circuitry that extracts power from the spare cable pairs. You can see a high-res version in the user manual. The signals are marked POE+2 and POE-2 in the schematic. The POE-2 signal (pins 4 and 5 of network connector) is routed to ground via solder jumper J3. This solder jumper is made by default. The POE+2 signal is routed to the Vaux pin on the X1 press-fit connector, via a 40V, 1A Schottky diode. Power sent via the spare pair on the network cable can thus be obtained via the GND and Vaux pins of the X1 and X2 press-fit connectors.