ENC28J60 Ehterent module

ENC28J60 chip contains Ethernet interface including 8kB buffer memory. The ENC28J60 chip communicates with the processor using SPI bus. ENC28J60 uses 3.3V supply voltage, however its input lines tolerate 5V. Note that the output line can not tolerate 5V, so ENC28J60 works with 5V master like Arduino, but will not tolerate a 5V slave on the same bus. In other words, all SPI slaves on the same SPI bus must use 3.3V signalling whan talking to the master.

This module is handled by ethercard Library in Arduino and Energia environments (the original library is specific to AVR processor, but in laboratory Energia contains modified version working with ARM processors). The library pretends to implement TCP/IP but in fact the implementation is quite restriced:

all packets are sent to a gateway, there is no way to directly send a packet to komputer different than the gateway
TCP requests must fit in a single packet

Note: There are two different kinds of ENC28J60 modules. One includes voltage regulator so that it can take power from 5V line. The other needs 3.3V supply. The ENC28J60 chip takes relatively large current (up to 180 mA), which is larger than nominal maximal current from 3.3V pin on most of our boards and USB serial convertors. So we will mostly use the version with voltage regulator and power it from 5V.