From: Lee A. <le...@ro...> - 2007-12-02 01:59:34
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I have an original audiostix and a connex 400. I'm running buildroot 1161 due to the 4 megs of flash on this board. I need to detect a voltage change from a switch which will act as a low RPM (400-1000) tachometer. It's really just a hacked bicycle speed sensor. After reading about GPIO lines I decided this was the right way to get some voltage changes into the gumstix. The audiostix has 10 exposed GPIO pins. I touched a multimeter to the pins and found that some output 3.3v and other output 0v. I tried to read the UCB1400 documentation to figure out how the pins correspond to the devices in /proc/gpio but I could not find a translation table. Then I found the gpio-event driver. I loaded the binary built for my kernel and enabled monitoring on GPIO devices 0-9 in /proc/gpio. The logic being that since there's no documentation of how the devices in userland correspond to the pins on the audiostix, maybe it's a literal translation. I'm monitor the first pin and use the 7th as the ground (as documented). The multimeter reads 3.3v. The moment that I run the gpio-event monitoring program, the multimeter drops to 0v. Now I cannot get it to output 3.3v again regardless of reboots. It appears that I broke something and I'm not sure what. I can't get the voltages from these pins back to their original state. How would I get pin 1 once again to output 3.3v to my sensor and detect when it drops to 0v as the switch opens? I have concluded I don't know how GPIO works but I haven't found any information on the mailing list or wiki about this subject beyond changing GPIO settings via /proc and running gpio-event. Both of which have done little for me except leave the system in an unknown state. Thanks for your help, Lee |