Active pin


I’m using an ALFAT SD board and I2C.

The datasheet says…[quote] “Active signal indicates the current status of command processing. Useful for a system-activity-LED, max 8mA. On UART: Active pin is high when a command is received and being processed. Low when command is complete. Note: The command is considered complete when ALFAT is done sending the response to the command. This is automatically completed in UART but SPI and I2C are slaves so ACTIVE pin will go low after the master reads the response. It is completely safe to ignore this signal and keep it not connected.”[/quote]

I have my active pin connected to an LED. It seems stuck high. I’m reading the bus, but I get a NULL back, and the light stays on. What (if anything) does this mean?

Note: I’m still able to send commands, such as V, J, I, O, etc… I get the response “!00”, but the light is still on

Because the commands were executed very fast that you do not see when the led turned off. You can scope it to verify.

@ solara.kane -

If an LED turns on when connect to active pin, there are 2 thing can be happened:

  • There are still some bytes in ALFAT need to be read
  • Check your LED, make sure you connect right way!