BananaPro, WiringLMK, i2c and GPIO pins

justwantin · 01-17-2016, 12:05 AM

I had inferred in this thread http://www.linuxquestions.org/questions/slackware-arm-108/%5B-lemaker-bananapi-%5D-usb-ports-seem-to-be-doa-4175561846/ that I did not have access to i2c on the arm7 kernel.

It turns out this is not the case. I had tried to access i2c using a command from the Lemaker from the WiringPi C library.

Code:

# gpio load i2c
modprobe: FATAL: Module i2c-sunxi not found in directory /lib/modules/4.2.6-armv7
gpio: Unable to load i2c-sunxi

However, after building/installing i2c-tools from a slackbuild and powering up a ds2482 i2c/one wire bridge connected to a ds2438 and the SDC/SCL pins on the Pro, the the arm7-4.2.6 i2c-dev module was loaded and the ds2482 was detected.

Code:

# i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- 18 -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --

Note that I had no problem using WiringLMK to access GPIO pins using but I haven't done much more than test by flashing LEDs yet.

WiringLMK by default installs in /usr/local but you can edit the makefile in the directory wiringLMK and change PREFIX to /usr and the DESTDIR to /somewhere/build to make a slackpkg.

I'd prefer to use a system numbering scheme for GPIO pins as I have done in bash scripts on Pi's but I haven't figured out the numbering (yet).... time.....?

louigi600 · 01-17-2016, 01:09 AM

I remember reading something about the gpio pin numbering on linux-sunxi.org.
There's a formula .... I've no idea how much of that still holds on newer kernels but here's the link anyway ... and here's what you should be looking for

Quote:

E.g for PH18 this would be ( 8 - 1) * 32 + 18 = 224 + 18 = 242 (since 'h' is the 8th letter).

justwantin · 01-17-2016, 02:49 AM

Thanks fo that, I just replied to your post in the other thread

Cheers

justwantin · 01-18-2016, 02:35 AM

Quote:

There's a formula .... I've no idea how much of that still holds on newer kernels

That's it. I remember now noting it on the back of a docket that went walkabout, couldn't remember where I saw it. This works with slackwarearm's arm7-4.2.6 kernel..... at least with physical pins 7 and 13, PH2 and PI18 which I have tested. For example: PH2=(8-1)*32=224+2=226

Code:

# echo "226" > /sys/class/gpio/export
# echo "out" > /sys/class/gpio/gpio226/direction
# echo "1" > /sys/class/gpio/gpio226/value
# echo "0" > /sys/class/gpio/gpio226/value and the following will swicth an LED on/off.