Link activity LEDs on UbiSwitch BaseBoard Mini

– Copied from customer email –

We are using single color leds , that support 2v input. Our goal is to make them provide acceptable brightness and to make them blink.

  1. Can we remove resistors R4 & R5 (to increase voltage for our leds) will everything else continue working as intended?
  2. According to your led schematics in your datasheet, when we are connecting our leds to “green” they don’t blink, they are just always on,

Is there a way to connect a single color led and make it blink?

The forum post below provides useful context on how the LEDs work on UbiSwitch.

The LED lines are multiplexed, so one line does not correspond directly to one LED signal. The schematic below shows how they are connected.

The lines named on the connector are shown below.

EE_CLK_C0_LED_P1_LED0_FLOW = C0_LED (C0 printed on the board)

By connecting the Column lines (C0, C1, C2, C3) and Row lines (R0, R1) in specific ways, you can access the LED lines as needed.

The table below shows how the rows and columns correspond to different LED signals. Each port has two LED signals associated with it, one for activity, and one for link.

R0_LED Port 1, LED0 Port 1, LED 1 Port 2, LED 0 Port 2, LED 1
R1_LED Port 3, LED0 Port 3, LED 1 Port 4, LED 0 Port 4, LED 1

Off = No Link
On = 1000M link
Blink = 1000BASE-T activity

Off = No Link
On = 10/100M link
Blink = 10/100 activity

These LED signals are designed for use with dual colour LEDs. This allows a single LED package to display both link speed information (with colour) and link activity information (off/on/blink).

To clarify how you connect an LED… For Port 1, 1000M link/activity LED, you would connect an LED between C0_LED (anode) and R0_LED (cathode).

If you are using a single colour LED, you would only be able to use either the 10/100M or the 1000M link/activity combination, which is not ideal.

You mention that your LEDs do not blink, and are always on. Please share your schematic for how you have connected your LEDs so we can check.

Regarding LED brightness, R4 and R5 (150 Ohm resistors) limit the current flowing in both the onboard LEDs, and your external LEDs. For your external LEDs, you can either add them directly on the LED header (in which case, the R4 and R5 will limit the current flowing through them), or you can add additional resistors in series with the external LEDs to reduce the brightness.

Note that the LED anodes (C0 to C3) are 3.3V level signals.

You should avoid modifying R4 and R5. Please note that modifying the board will void the warranty.

Added note…

The LED0 signals show link/activity for 1000M.
The LED1 signals show link/activity for 10/100M.

For reference, for port 1, 1000M, you should use…

Port 1 1000M Activity LED:

C0 (anode) ---------|>|----------- R0 (cathode)