Connecting the BeagleBone Black with mikroE Click Boards/mikroBus Cape help wanted
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TL;DR: How to access a mikroE click module via SPI using a BeagleBone Black and a mikroBus Cape?
Hello,
I'm currently trying to connect my BeagleBone Black Rev C with the mikroBus Cape (PID: MIKROE-1857).
Furthermore, I want to get access to a MRAM click module (https://www.mikroe.com/mram-click) by connecting it with the mikroBus Cape. My BBB is running the latest Debian image (AM3358 Debian 10.3 2020-04-06 4GB SD IoT) and with uname_r=4.14.108-ti-r141.
Firstly, I tried to work with U-Boot overlays:
I followed the instructions on https://elinux.org/Tigal:BeagleBone_mikrobuscape but used the updated url "https://github.com/mikroe/BBB-mikroBUS-Cape". But, after setting the "uboot_overlay_addr0=/lib/firmware/BB-MIKROBUS-01-00A1.dtbo" in the uEnv.txt the board would not boot.
I followed the instructions on "https://github.com/beagleboard/bb.org-overlays/" and I also upgraded my bootloader (https://elinux.org/Beagleboard:BeagleBoneBlack_Debian#U-Boot_Overlays). After setting all four BB-MIKROBUS-CAPE-X.dtbo files in "uboot_overlay_addrY=..." the board booted. (It also boots when only one is enabled)
Next I wanted to get access to the click module on the mikroBus Cape.
A.
I downloaded the mikroSDK 2.0 (https://www.mikroe.com/mikrosdk) on the BBB, but I couldn't find nor create the correct board.h file to get it running. After stumbling upon "NectoStudio" I could only find support for generic ARM boards which are from the STM32 family, which the BBB Rev C is not. (Getting access to the mikroSDK 2.0 would allow the usage of scripts via https://libstock.mikroe.com/ which would open up many other possibilities)
As I couldn't get the mikroSDK 2.0 working, I tried to get direct access via SPI to the click module. For that I put the click module on the mikroBus Cape slot 3 (CS - Pin 17, D1/MISO - Pin 21, D0/MOSI - Pin 18 and CLK - Pin 22).
B.
After some research I found the iobb library and followed its instructions
(https://www.element14.com/community/community/designcenter/single-board-computers/next-genbeaglebone/blog/2019/08/15/beaglebone-black-bbb-io-gpio-spi-and-i2c-library-for-c-2019-edition).
After installation, I tried to run the example SPI code without any changes (so not using option 2.) and it runs error-free. But when I enable the BB-MIKROBUS-CAPE-3.dtbo I always get "ERROR: open() for /sys/devices/platform/ocp/ocp:P9_17_pinmux/state failed, No such file or directory" So, after some investigation I realised that BB-MIKROBUS-CAPE-3.dtbo sets "P9_X_pinmux { status = "disabled"; };" for X = {18,19,21,22} and doesn't enable spi in its pinctrl-section, which could be the cause for the problem.
So I tried two things:
- I just used BB-MIKROBUS-CAPE-2.dtbo which doesn't set "P9_X_pinmux { status = "disabled"; };" for any X = {18,19,21,22} and the example code ran error-free.
- I changed BB-MIKROBUS-CAPE-3.dtbo so that spi gets enabled in the pinctrl-section and the example code ran error-free.
To my understanding both of this ways should enable SPI, but when I try to read previously written data from the click module, I can't receive any data at all or select a cell to write to.
So, is there a way to get any of my attempts working so that I can get access to the click module via SPI? Or have I overlooked an other solution?
Btw:
- I tried all solutions on the board itself and on a microSD card which I set up using https://beagleboard.org/getting-started
- I also tried it with and without setting "disable_uboot_overlay_video=1" in the uEnv.txt
Please ask for support on forum.beagleboard.org. If resolved, please close this issue and point to the discussion. If unable to resolve, please contact me via my calendar at https://beagleboard.org/about/jkridner.
The issues were due to an internal error of the beagle bone.