It's Ethernet, from an SPI interface
Over the years, as microcontrollers have become fast enough to do the heavy lifting, we've grown accustomed to 10 Megabit Ethernet being modified by interfaces it wasn't meant to come out of. We believe, however, that we've never seen one driven from an SPI interface, so [Ivan's] may be a first. With a smartly designed transceiver using logic chips, it even offers a chance to understand something about timing an Ethernet interface.
Differential logic signals derived from a simple Ethernet transceiver can be read by an SPI bus, but without a clock line. The challenge then was to build a circuit that would construct the required clock pulses from state changes on the data line. This would become a monostable with an XOR gate and a shift register to manage the clock during the preamble phase.
The resulting circuit fits nicely on a shield for the ST Nucleo 64 board, where while it might not be the obvious choice for an Ethernet shield, it certainly does the trick.
>If Unexpected Ethernet is your thing, how about the i2s device on an ESP8266?
Over the years, as microcontrollers have become fast enough to do the heavy lifting, we've grown accustomed to 10 Megabit Ethernet being modified by interfaces it wasn't meant to come out of. We believe, however, that we've never seen one driven from an SPI interface, so [Ivan's] may be a first. With a smartly designed transceiver using logic chips, it even offers a chance to understand something about timing an Ethernet interface.
Differential logic signals derived from a simple Ethernet transceiver can be read by an SPI bus, but without a clock line. The challenge then was to build a circuit that would construct the required clock pulses from state changes on the data line. This would become a monostable with an XOR gate and a shift register to manage the clock during the preamble phase.
The resulting circuit fits nicely on a shield for the ST Nucleo 64 board, where while it might not be the obvious choice for an Ethernet shield, it certainly does the trick.
>If Unexpected Ethernet is your thing, how about the i2s device on an ESP8266?
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