How are the LED signals on the breakout header on GigaBlox Rugged wired?

– Copied from customer query –

I’m currently designing a PCB to interface with the GigaBlox Rugged Gigabit Switch LED header - with D1-8, and VCC. Which LED output is for which colour / port? It’s not clear from the datasheet.

You’re right, this is not clear from the datasheet. Below is the header pinout.

The leds work in 2 bit mode, so the two signals are combined to show port speed as colour, and port activity as blinking.

1Gbps link = Green LED on, Red LED off.
100Mbps link = Green and Red LED on (Orange colour)
10Mbps link = Green LED off, Red LED On

When there is traffic, the LEDs that are on will blink. For example, this results in a blinking orange LED for activity on a 100Mbps link, and a linking green LED for activity on a 10Mbps link.

Port 1
D1 - Green LED
D2 - Red LED

Port 2
D3 - Green LED
D4 - Red LED

Port 3
D5 - Green LED
D6 - Red LED

Port 4
D7 - Green LED
D8 - Red LED

So if you will always have a 1G or 100M link, you can just use the green LED as a port activity indicator. If you could have a 1G, 100M or 10M link, then you need to use both signals, either on a dual color LED, or by ORing the signals to get a single signal for port activity.

Note that there is already a 1K resistor on the anode of each line, so you can add an external LED directly without needing to add a current limiting resistor.