diff --git a/README.MD b/README.MD index 0acb3a3..964161d 100644 --- a/README.MD +++ b/README.MD @@ -17,10 +17,15 @@ When writing it, the following were the main design philosophies: ## Hardware -TBD. TL;DR: +![Circuit Diagram](doc/circuit.svg) -* RX: Use resistors behind Ethernet magnetics to reduce Ethernet RX voltage levels (0 +-2.5V) to LVPECL voltage levels (1.65V +-400mV). Or LVDS if your FPGA can't handle LVPECL. -* TX: Meh, a series current limiting resistor is good enough. +* RX: Use resistors behind Ethernet magnetics to reduce Ethernet RX voltage levels (0 +-2.5V) to LVPECL voltage levels (1.65V +-400mV). Or LVDS if your FPGA can't handle LVPECL. Also, pull up/down resistors help to avoid glitchy behavior with no cable connected or little data activity. +* TX: Meh, a series current limiting resistor is good enough. Drive two outputs differentially to increase the voltage swing. (Technically not true antivalent signals as there's also the "off" state with both disabled.) + +Notes: + +* The RX pull up/downs are probably not the best idea, and fixable in a better way. But for now, this shall work -- and suffice! +* On the TX side, I'm grossly overloading the drivers. A line driver would probably be a good idea. Or you can just parallel multiple outputs ;D ## License diff --git a/doc/circuit.svg b/doc/circuit.svg new file mode 100644 index 0000000..3890d20 --- /dev/null +++ b/doc/circuit.svg @@ -0,0 +1,3039 @@ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +