From: Chris G <chr...@qi...> - 2012-11-29 00:20:52
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I gathered some more information today. Using devmem2, I can set the MOSI pin to mode 4, making it GPIO172. Then I export the GPIO, set the direction to output, and am able to toggle between 0V and 1.8V just fine. But when I try the same with the MISO pin (setting it to GPIO173, export, set direction to out), it only toggles between 0 and 0.4V. I have verified this behavior on 3 EarthSTORM and Chestnut43 board pairs, one of which was right out of the box, with both custom and factory linux images, with the 40-pin header connected and disconnected. The only conclusion I can draw right now is that something on either the Chestnut or the EarthSTORM is somehow bogging down that MISO/GPIO173 pin. In the input state, it doesn't seem to be going into high-impedance mode. It's either a design problem, or some subtle configuration register I'm missing. It would be great if someone could verify this independently for me with some combination of EarthSTORM or Chestnut since I'm not even sure how to proceed now. Here's a log of what I did from boot-up, verifying that the MISO pin (pin 7 on the 40-pin header) only goes to 0.4V instead of 1.8V when high. Thanks for anything. root@overo:~# devmem2 0x480021CC /dev/mem opened. Memory mapped at address 0x40145000. Read at address 0x480021CC (0x401451cc): 0x01080100 root@overo:~# devmem2 0x480021CC w 0x01080004 /dev/mem opened. Memory mapped at address 0x40191000. Read at address 0x480021CC (0x401911cc): 0x01080100 Write at address 0x480021CC (0x401911cc): 0x01080004, readback 0x01080004 root@overo:~# echo 173 > /sys/class/gpio/export root@overo:~# echo out > /sys/class/gpio/gpio173/direction root@overo:~# echo 1 > /sys/class/gpio/gpio173/value root@overo:~# echo 0 > /sys/class/gpio/gpio173/value -- View this message in context: http://gumstix.8.n6.nabble.com/SPI-MISO-only-problem-driving-the-input-tp4966160p4966181.html Sent from the Gumstix mailing list archive at Nabble.com. |