Hi, Platform: ubuntu-core-12.04.4-core-armhf, board UDOO duo. I am strugling for a day or so to read the temperature humidity sensor SEN-10167 using bcm2835 and Adafruit taken from RPI. Also I tried the sample rht03 from wiringPI. SO far looks like none of the libraries above can conrol any of the GPIO's, though catting echoing in /sys/.../gpio137/<> works. I tried also mimic the SEN-10167 protocol, in a C program reading /sys/ files back and forward, but... dealing with files io seems to slow to process the serial 1 bit protocol. Looks like a fopen/fread/fclose takes much more Total time elapsed : 214 us Total time elapsed : 203 us than 28 us for reading a bit and does not catch the timeframe to detect 1-ns and 0-es. Keeping the FILE* open then reading fails in all subseqent reads, returning noting, so I have to open-read-close. Any ideas how the above libraries don't conplain with bcm controller on UDOO, or to performe a read from gpio file under 4 uSeconds ?. Any other work arounds, or drivers to access the GPIO as on RPI. The bcm lib along with and Adafruit works simless on RPI. I have to do this from Linux not from ardu schetch Thank you.
Hello @marlus, Can you please explain how you solved? Am experiencing kind of similar problem over here. Also, how did you compile/execute your code? i know this might sound trivial, but am new to this area and I've absolutely no idea about how to execute a C program that manipulates GPIO on UDOO. Please help! Thank you!
Ohh, I did not port the bcm2835 to UDOO-DUO. I need a fast way to access the GPIO's so I can implement the 1 wire RTH03 protocol. I enabled in kernel the GPIO memory map suport, and I am reading/writing the gpios accessing the memory map. I am sorry about the bcm2835, but all I need it was a gpio fast access. (sorry , I did not read you are new!) Here is the Kernel build procedure. You have to get the kernel: https://github.com/UDOOboard/Kernel_Unico Code: sudo apt-get install git git clone https://github.com/UDOOboard/Kernel_Unico Get the cross compiler http://udoo.org/download/files/crosscom ... abi.tar.gz Unzip the cross compiler in ~/CC folder, and gitting kernel creates ~/Kernel_Unico, so: Then at a shell prompt: Code: export CROSS_COMPILE=../CC/arm-fsl-linux-gnueabi/bin/arm-fsl-linux-gnueabi- export ARCH=arm modules cp ./.config ./.config-retired # backup curent config in case of screwing up cp ./arch/arm/configs/UDOO_defconfig ./arch/arm/configs/UDOO_defconfig-retired # backup UDOO config in case of screwing up cp ./arch/arm/configs/UDOO_defconfig ./.config # overwrite curent config make xconfig #see the attached picture, enable gpiommap, save # change it cp ./.config ./arch/arm/configs/UDOO_defconfig # make the USOO be what you want make UDOO_defconfig # not quite required in this scenario make # makes the uImage and so ... You have to copy the kernel uImage from arch/arm/boot/uImage to the sdcard /boot/uImage (save the old uImage fom card in case of...) Now you can access the gpio's like here http://elinux.org/RPi_Low-level_peripherals @ GPIO Code examples How to: (in Ubuntu) get a compiler: Code: sudo apt-get install gcc sudo apt-get install g++ sudo apt-get install make sudo apt-get install nmake As a beginer get a IDE so you dont want to write by hand Makefiles Code: sudo apt-get install codeblocks Read here: http://learnconlinux.blogspot.ca/ and here first http://www.howtoforge.com/learning-c-cp ... ep-by-step
Hi marius, have you measured how fast can you read from GPIO pin using mmap? I'm interested since as you I need to read as fast as possible from pins, so sysfs access is not viable.
