Left front red LED always on

Just received the 3pi expansion board to make it an m3pi. Decided to put mbed in control, and 3pi as slave, as suggested. Installed serial-slave on 3pi. Right away noticed left bottom (and top) red LED now always lit.
Tried two examples programing the mbed: HelloWorld which sends robot out about a foot, spins 180, comes back, and spins 180 again and stops. Red LED always lit. Simple line-follower program works, but LED still on.
Looked through the mbed Cookbook. Don’t see any way to control LEDS on the 3pi from mbed expansion board. And maybe many other functions on the 3pi.

Hi, donde.

The red LED on the 3pi is connected to a serial line, so when the 3pi’s serial module is enabled the red LED will be lit. It should flicker when the 3pi is transmitting, but it might be hard to see given the high baud rate. The red LEDs connected to the mbed are partially on when it starts because the mbed defaults to having pullups enabled on its IO pins. If you make the first line of your mbed program turn off the LEDs, they should turn off pretty quickly.

- Ryan

Hi Ryan,
How would I turn off the left red LED on the 3pi from the mbed language? Or would I also include:
#include <pololu/3pi.h>
#include <avr/io.h>
And then use: left_led(0);
or red_led(0);


You can’t turn off the red LED on the 3pi in code because it is connected to the serial port, which, if you want the mbed and the 3pi to be able to communicate, you cannot turn off.

- Ryan

I thought maybe I could share on the forum, but appreciate your help on Yahoo. I have not seen any posts on the forum for m3pi and wondering why?
Thanks, donde

Forgot to ask. How do I function another LED, other than the “serial port LED”, on the 3pi from the mbed?

I guess people aren’t asking questions because they don’t have any. Unfortunately, the serial slave program does not have a command for changing the 3pi Robot’s green LED. The only actions the mbed can command the 3pi to perform are the ones listed in the serial slave documentation. If you wanted to change the state of the green LED, you would have to modify the serial slave program, adding a new command to do it.

- Ryan

OK Ryan,

I looked closer and there are a few forum comments on m3pi. I suppose there will more in the future. Think I’ll look at mbed outside the 3pi environment for a while to get more familiar with it. I see lots of example programs on the mbed site.

Thanks, Don