Hi all, i was trying to follow this LED tutorial and experienced an unexpected result. I had everything hooked up the way the video instructs, with some exception(s): at this time i do not have a breadboard or jumper wires, so i was trying to wing it with some test leads and some header pins that i removed from an old PackardBell desktop motherboard. I soldered a pin onto one end of two wires and stripped the other ends for alligator clip connection. i hooked up my LED as shown in the video, except using test leads with alligator clips for connection(s). Also, i did not have a 220Ohm resistor as the tut prescribes, however i had a 180 Ohm that i clipped off of a scrap pcb a while back. I held the LED to a 9v battery and it was REALLY BRIGHT for about one second, and then it ceased to function. So i got another LED, (luckily i had more than one lol) and clipped the resistor to the positive leg of the LED with a test lead, then applied my 9v battery (which read ~7.5v on my multimeter) and the resistor seemed to work well, the LED was a “normal” brightness and it continued to function until i removed the battery, so i assumed it worked well enough to use.
Here’s where the unexpected things start happening. I hook up my little setup to the BBB and plug it in, expecting that the LED would be unlit. However when the BBB started to boot, the LED came on and for a moment mimicked either the USR3 or USR4 LED on the board. After boot was complete the LED remained lit but very dim. I continued in my attempt to follow the tutorial, entering all commands as instructed and verbatim.
The commands i entered are as follow
echo 38 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio38/direction
echo 1 > /sys/class/gpio/gpio38/value
echo 0 > /sys/class/gpio/gpio38/value
echo 38 > /sys/class/gpio/unexport
now, when I changed the value for the pin, nothing happened at all, the LED stayed the same, very dimly lit. I changed the value from 1 to 0 to 1 several times and observed no change at the LED. I figured obviously either something is wrong or i DID something wrong, so i put everything back the way i found it and shut her down. I am confused because this is not what i expected, i was happy to get an LED to glow, but i can do that with a 9v battery and a scrap resistor, so using a $45 computer to do it isnt all that great, if I can't program the output.
Anyone care to take a stab at what (probably obvious) thing i might be doing wrong? I know the tut is for BBW but i checked the SRM and the pin is the same as in the tut (GPIO1_6). Commands were issued from GateOne running in Chrome browser on ubuntu 12.10 x64. Software on the BBB is the original SW that shipped with the board.
Is there something in the BBB that is different from the BB that I am not accounting for? Is the LED supposed to be completely off when i boot up the board? That's kinda what I expected because that's what the video shows happening.
Anyone know what I did wrong? Do I need to update my SW? I heard about ppl accidentally wiping their eMMC and it kinda deterred me from wanting to update anything...