Using mikroBUS#

Steps:

  1. Identify if mikroBUS add-on includes a ClickID with manifest. If not, manifest must be supplied.

  2. Identify if mikroBUS add-on is supported by the kernel. If not, kernel module must be added.

  3. Identify how driver exposes the data: IIO, net, etc.

  4. Connect and power

  5. Verify and utilize

Using boards with ClickID#

What is mikroBUS?#

mikroBUS is an open standard for add-on boards for sensors, connectivity, displays, storage and more with over 1,400 available from just a single source, MikroE. With the flexibility of all of the most common embedded serial busses, UART, I2C and SPI, along with ADC, PWM and GPIO functions, it is a great solution for connecting all sorts of electronics.

Note

Learn more at https://www.mikroe.com/mikrobus

What is ClickID?#

ClickID enables mikroBUS add-on boards to be identified along with the configuration required to use it with the mikroBUS Linux driver. The configuration portion is called a manifest.

Note

Learn more at MikroElektronika/click_id

BeaglePlay’s Linux kernel is patched with a mikrobus driver that automatically reads the ClickID and loads a driver, greatly simplifying usage.

Does my add-on have ClickID?#

Look for the board’s 'D (ID) logo. It’s near the PWM pin on the upper right-hand side in the illustration below.

mikroBUS clickID - BeaglePlay connection

Fig. 174 mikroBUS clickID - BeaglePlay connection#

If your add-on has ClickID, simply connect it while BeaglePlay is powered off and then apply power.

Example of examining boot log to see a ClickID was detected.

debian@BeaglePlay:~$ dmesg | grep mikrobus
[    2.096254] mikrobus:mikrobus_port_register: registering port mikrobus-0
[    2.096325] mikrobus mikrobus-0: mikrobus port 0 eeprom empty probing default eeprom
[    2.663698] mikrobus_manifest:mikrobus_manifest_attach_device: parsed device 1, driver=opt3001, protocol=3, reg=44
[    2.663711] mikrobus_manifest:mikrobus_manifest_parse:  Ambient 2 Click manifest parsed with 1 devices
[    2.663783] mikrobus mikrobus-0: registering device : opt3001

Note

Not all Click boards with ClickID have valid manifest entries. Then you can follow What if my add-on has invalid manifest entries? to make your add-on detected.

To use the add-on, see Accel Click Board Example.

What if my add-on doesn’t have ClickID?#

If add-on doesn’t have clickID then it can not be detected directly.

debian@BeaglePlay:~$ dmesg | grep mikrobus
[    2.123994] mikrobus:mikrobus_port_register: registering port mikrobus-0
[    2.124059] mikrobus mikrobus-0: mikrobus port 0 eeprom empty probing default eeprom

Available manifest can be installed that has been created for your add-on as we have created over 100 of them. You can install the existing manifest files onto your BeaglePlay. First, make sure you have the latest manifests installed in your system.

sudo apt update
sudo apt install bbb.io-clickid-manifests

Take a look at the list of manifest files to see if the Click or other mikrobus add-on board manifest is installed.

debian@BeaglePlay:~$ ls /lib/firmware/mikrobus/
10DOF-CLICK.mnfb          COMPASS-2-CLICK.mnfb       I2C-2-SPI-CLICK.mnfb        PWM-CLICK.mnfb
13DOF-2-CLICK.mnfb        COMPASS-CLICK.mnfb         I2C-MUX-CLICK.mnfb          RFID-CLICK.mnfb
3D-HALL-3-CLICK.mnfb      CURRENT-CLICK.mnfb         ILLUMINANCE-CLICK.mnfb      RF-METER-CLICK.mnfb
3D-HALL-6-CLICK.mnfb      DAC-7-CLICK.mnfb           IR-GESTURE-CLICK.mnfb       RMS-TO-DC-CLICK.mnfb
6DOF-IMU-2-CLICK.mnfb     DAC-CLICK.mnfb             IR-THERMO-2-CLICK.mnfb      RTC-6-CLICK.mnfb
6DOF-IMU-4-CLICK.mnfb     DIGIPOT-3-CLICK.mnfb       LED-DRIVER-7-CLICK.mnfb     SHT1x-CLICK.mnfb
6DOF-IMU-6-CLICK.mnfb     DIGIPOT-CLICK.mnfb         LIGHTRANGER-2-CLICK.mnfb    SHT-CLICK.mnfb
6DOF-IMU-8-CLICK.mnfb     EEPROM-2-CLICK.mnfb        LIGHTRANGER-3-CLICK.mnfb    SMOKE-CLICK.mnfb
9DOF-CLICK.mnfb           EEPROM-3-CLICK.mnfb        LIGHTRANGER-CLICK.mnfb      TEMP-HUM-11-CLICK.mnfb
ACCEL-3-CLICK.mnfb        EEPROM-CLICK.mnfb          LPS22HB-CLICK.mnfb          TEMP-HUM-12-CLICK.mnfb
ACCEL-5-CLICK.mnfb        ENVIRONMENT-CLICK.mnfb     LSM303AGR-CLICK.mnfb        TEMP-HUM-3-CLICK.mnfb
ACCEL-6-CLICK.mnfb        ETH-CLICK.mnfb             LSM6DSL-CLICK.mnfb          TEMP-HUM-4-CLICK.mnfb
ACCEL-8-CLICK.mnfb        ETH-WIZ-CLICK.mnfb         MAGNETIC-LINEAR-CLICK.mnfb  TEMP-HUM-7-CLICK.mnfb
ACCEL-CLICK.mnfb          FLASH-2-CLICK.mnfb         MAGNETIC-ROTARY-CLICK.mnfb  TEMP-HUM-9-CLICK.mnfb
ADC-2-CLICK.mnfb          FLASH-CLICK.mnfb           MICROSD-CLICK.mnfb          TEMP-HUM-CLICK.mnfb
ADC-3-CLICK.mnfb          GENERIC-SPI-CLICK.mnfb     MPU-9DOF-CLICK.mnfb         TEMP-LOG-3-CLICK.mnfb
ADC-5-CLICK.mnfb          GEOMAGNETIC-CLICK.mnfb     MPU-IMU-CLICK.mnfb          TEMP-LOG-4-CLICK.mnfb
ADC-8-CLICK.mnfb          GNSS-4-CLICK.mnfb          NO2-2-CLICK.mnfb            TEMP-LOG-6-CLICK.mnfb
ADC-CLICK.mnfb            GNSS-7-CLICK.mnfb          NO2-CLICK.mnfb              THERMO-12-CLICK.mnfb
AIR-QUALITY-2-CLICK.mnfb  GNSS-ZOE-CLICK.mnfb        OLEDB-CLICK.mnfb            THERMO-15-CLICK.mnfb
AIR-QUALITY-3-CLICK.mnfb  GSR-CLICK.mnfb             OLEDC-CLICK.mnfb            THERMO-17-CLICK.mnfb
AIR-QUALITY-5-CLICK.mnfb  GYRO-2-CLICK.mnfb          OLEDW-CLICK.mnfb            THERMO-3-CLICK.mnfb
ALCOHOL-2-CLICK.mnfb      GYRO-CLICK.mnfb            OZONE-2-CLICK.mnfb          THERMO-4-CLICK.mnfb
ALCOHOL-3-CLICK.mnfb      HALL-CURRENT-2-CLICK.mnfb  PRESSURE-11-CLICK.mnfb      THERMO-7-CLICK.mnfb
ALTITUDE-3-CLICK.mnfb     HALL-CURRENT-3-CLICK.mnfb  PRESSURE-3-CLICK.mnfb       THERMO-8-CLICK.mnfb
ALTITUDE-CLICK.mnfb       HALL-CURRENT-4-CLICK.mnfb  PRESSURE-4-CLICK.mnfb       THERMO-CLICK.mnfb
AMBIENT-2-CLICK.mnfb      HDC1000-CLICK.mnfb         PRESSURE-CLICK.mnfb         THERMOSTAT-3-CLICK.mnfb
AMBIENT-4-CLICK.mnfb      HEART-RATE-3-CLICK.mnfb    PROXIMITY-10-CLICK.mnfb     UV-3-CLICK.mnfb
AMBIENT-5-CLICK.mnfb      HEART-RATE-4-CLICK.mnfb    PROXIMITY-2-CLICK.mnfb      VACUUM-CLICK.mnfb
AMMETER-CLICK.mnfb        HEART-RATE-5-CLICK.mnfb    PROXIMITY-5-CLICK.mnfb      VOLTMETER-CLICK.mnfb
COLOR-2-CLICK.mnfb        HEART-RATE-7-CLICK.mnfb    PROXIMITY-9-CLICK.mnfb      WAVEFORM-CLICK.mnfb
COLOR-7-CLICK.mnfb        HEART-RATE-CLICK.mnfb      PROXIMITY-CLICK.mnfb        WEATHER-CLICK.mnfb

Below command to grant root privileges of the intended user and then enter passsword. This will take you to the different shell.

sudo su

Then, load the appropriate manifest using the mikrobus bus driver. For example, with the Ambient 2 Click, you can write that manifest to the mikrobus-0 new_device entry.

cat /lib/firmware/mikrobus/AMBIENT-2-CLICK.mnfb > /sys/bus/mikrobus/devices/mikrobus-0/new_device

You can now exit this shell.

exit

Once done, you can check it using command dmesg | grep mikrobus which shows that add-on is now detected.

debian@BeaglePlay:~$ dmesg | grep mikrobus
[    2.096254] mikrobus:mikrobus_port_register: registering port mikrobus-0
[    2.096325] mikrobus mikrobus-0: mikrobus port 0 eeprom empty probing default eeprom
[    2.663698] mikrobus_manifest:mikrobus_manifest_attach_device: parsed device 1, driver=opt3001, protocol=3, reg=44
[    2.663711] mikrobus_manifest:mikrobus_manifest_parse:  Ambient 2 Click manifest parsed with 1 devices
[    2.663783] mikrobus mikrobus-0: registering device : opt3001

Note

It’ll forget on reboot… need to have a boot service.

Todo

To make it stick, …

What if my add-on has invalid manifest entries?#

Not all Click boards with ClickID have valid manifest entries. If your add-on has clickID but shows the command output like below.

debian@BeaglePlay:~$ dmesg | grep mikrobus
[    2.119771] mikrobus:mikrobus_port_register: registering port mikrobus-0
[    2.119842] mikrobus mikrobus-0: mikrobus port 0 eeprom empty probing default eeprom
[    2.261113] mikrobus_manifest:mikrobus_manifest_header_validate: manifest version too new (150.189 > 0.3)
[    2.261130] mikrobus mikrobus-0: invalid manifest size -22

There are some available manifest that can be used to write in the eeprom of clickID board. Once you sudo apt update and sudo apt install bbb.io-clickid-manifests then you can see the list of manifests using command ls /lib/firmware/mikrobus/. Let’s take the Accel Click - ClickID Board with invalid manifest entries, To get the valid manifest we need to write ACCEL-CLICK.mnfb to eeprom of ClickID board using the following commands.

First check the file name for the add-on device. It can be in the form of w1_bus_master1-xx-xxxxxxx.

debian@BeaglePlay:~$ ls /sys/bus/w1/devices/
w1_bus_master1  w1_bus_master1-xx-xxxxxxx

Then in the following command, /lib/firmware/mikrobus/ACCEL-CLICK.mnfb is the path of manifest file and /sys/bus/w1/devices/w1_bus_master1-xx-xxxxxxx/mikrobus_manifest is path for one wire eeprom clickID board. You must replace the the file name w1_bus_master1-xx-xxxxxxx with your clickID board file in the below command.

debian@BeaglePlay:~$ sudo dd if=/lib/firmware/mikrobus/ACCEL-CLICK.mnfb of=/sys/bus/w1/devices/w1_bus_master1-xx-xxxxxxx/mikrobus_manifest
0+1 records in
0+1 records out
132 bytes copied, 0.0144496 s, 9.1 kB/s

Now, Reboot your BeaglePlay. After rebooting, the add-on has been detected with valid manifest entries.

debian@BeaglePlay:~$ dmesg | grep mikrobus
[    2.126654] mikrobus:mikrobus_port_register: registering port mikrobus-0
[    2.126727] mikrobus mikrobus-0: mikrobus port 0 eeprom empty probing default eeprom
[    2.797179] mikrobus_manifest:mikrobus_manifest_attach_device: parsed device 1, driver=adxl345, protocol=3, reg=1d
[    2.797191] mikrobus_manifest:mikrobus_manifest_parse:  Accel Click manifest parsed with 1 devices
[    2.797267] mikrobus mikrobus-0: registering device : adxl345

Note

The updation has done in the eeprom of clickID board. It will not forget after reboot.

Note

We will be adding a link to the mikrobus-0 device at /dev/play/mikrobus in the near future, but you can find it for now at /sys/bus/mikrobus/devices/mikrobus-0. If you need to supply an ID (manifest), this is the directory where you will do it.

Manifesto: https://git.beagleboard.org/beagleconnect/manifesto

Patched Linux with out-of-tree Mikrobus driver: https://git.beagleboard.org/beagleboard/linux

To use the add-on, see Accel Click Board Example.

Accel Click Board Example#

Next, let’s explore how to read raw sensor values using the Accel Click board. This step will help us understand the basics of sensor data retrieval and processing.

First, let’s check the IIO devices available.

debian@BeaglePlay:~$ ls /sys/bus/iio/devices/
iio:device0  iio:device1

Considering the device iio:device0 is the MikroBUS click ID connected to the BeaglePlay board. Depending on your specific setup and device configuration, you might need to adjust the path or device number (device0) accordingly. In this case device0 corresponds to our Accel Click, let’s check its name.

debian@BeaglePlay:~$ cat /sys/bus/iio/devices/iio\:device0/name
adxl345

The file corresponding to the IIO device, including raw values, can be viewed using the following command:

debian@BeaglePlay:~$ ls /sys/bus/iio/devices/iio\:device0
dev                          in_accel_scale        in_accel_x_raw        in_accel_y_raw        in_accel_z_raw  power                         subsystem
in_accel_sampling_frequency  in_accel_x_calibbias  in_accel_y_calibbias  in_accel_z_calibbias  name            sampling_frequency_available  uevent

To view the raw values from the accel click (assuming iio:device0 is configured correctly for your MikroBUS click ID on the BeaglePlay board), you can use the following command:

debian@BeaglePlay:~$ cat /sys/bus/iio/devices/iio\:device0/in_accel_x_raw
3

This command reads and displays the raw X-axis accelerometer data from iio:device0. You can replace in_accel_x_raw with in_accel_y_raw or in_accel_z_raw to view raw data from the Y-axis or Z-axis accelerometer channels respectively, depending on your requirements.

To create a script displays accelerometer raw data values from iio:device0 use nano accelclick.sh command. Copy the below script and paste it to the accelclick.sh file. It reads the raw X, Y, and Z axis values from /sys/bus/iio/devices/iio:device0/in_accel_x_raw, /sys/bus/iio/devices/iio:device0/in_accel_y_raw, and /sys/bus/iio/devices/iio:device0/in_accel_z_raw respectively.

X=$(cat /sys/bus/iio/devices/iio\:device0/in_accel_x_raw)
Y=$(cat /sys/bus/iio/devices/iio\:device0/in_accel_y_raw)
Z=$(cat /sys/bus/iio/devices/iio\:device0/in_accel_z_raw)
echo "X = ${X}        Y = ${Y}      Z= ${Z}"

Note

Adjust the device path iio:device0 according to your setup. Also, ensure that your system and hardware configuration are correctly set up to provide live accelerometer data through these paths.

To make the script file executable, use the following command:

debian@BeaglePlay:~$ chmod +x accelclick.sh

When you run watch -n 0.5 ./accelclick.sh, the watch command will execute ./accelclick.sh every 0.5 seconds and display its output in the terminal.

debian@BeaglePlay:~$ watch -n 0.5 ./accelclick.sh

This is the output of your accelclick.sh script. It shows the current values of your accelerometer’s X, Y, and Z axis in raw form.

Every 0.5s: ./accelclick.sh

X = 3        Y = 11      Z= 284

Using boards with Linux drivers#

Depending on the type of mikrobus add-on board, the Linux driver could be of various different types. For sensors, the most common is IIO driver.

IIO driver#

Per https://docs.kernel.org/driver-api/iio/intro.html,

The main purpose of the Industrial I/O subsystem (IIO) is to provide support for devices that in some sense perform either analog-to-digital conversion (ADC) or digital-to-analog conversion (DAC) or both. The aim is to fill the gap between the somewhat similar hwmon and input subsystems. Hwmon is directed at low sample rate sensors used to monitor and control the system itself, like fan speed control or temperature measurement. Input is, as its name suggests, focused on human interaction input devices (keyboard, mouse, touchscreen). In some cases there is considerable overlap between these and IIO.

Devices that fall into this category include:

  • analog to digital converters (ADCs)

  • accelerometers

  • capacitance to digital converters (CDCs)

  • digital to analog converters (DACs)

  • gyroscopes

  • inertial measurement units (IMUs)

  • color and light sensors

  • magnetometers

  • pressure sensors

  • proximity sensors

  • temperature sensors

See also https://wiki.analog.com/software/linux/docs/iio/iio.

To discover IIO driver enabled devices, use the iio_info command.

debian@BeaglePlay:~$ iio_info
Library version: 0.24 (git tag: v0.24)
Compiled with backends: local xml ip usb
IIO context created with local backend.
Backend version: 0.24 (git tag: v0.24)
Backend description string: Linux BeaglePlay 5.10.168-ti-arm64-r104 #1bullseye SMP Thu Jun 8 23:07:22 UTC 2023 aarch64
IIO context has 2 attributes:
        local,kernel: 5.10.168-ti-arm64-r104
        uri: local:
IIO context has 2 devices:
        iio:device0: opt3001
                1 channels found:
                    illuminance:  (input)
                        2 channel-specific attributes found:
                                attr  0: input value: 163.680000
                                attr  1: integration_time value: 0.800000
                2 device-specific attributes found:
                                attr  0: current_timestamp_clock value: realtime
                                attr  1: integration_time_available value: 0.1 0.8
                No trigger on this device
        iio:device1: adc102s051
                2 channels found:
                        voltage1:  (input)
                        2 channel-specific attributes found:
                                attr  0: raw value: 4084
                                attr  1: scale value: 0.805664062
                        voltage0:  (input)
                        2 channel-specific attributes found:
                                attr  0: raw value: 2440
                                attr  1: scale value: 0.805664062
                No trigger on this device

Note that the units are standardized for the IIO interface based on the device type. If raw values are provided, a scale must be applied to get to the standardized units.

Storage driver#

Network driver#

How does ClickID work?#

Disabling the mikroBUS driver#

If you’d like to use other means to control the mikroBUS connector, you might want to disable the mikroBUS driver. This is most easily done by enabling a device tree overlay at boot.

Todo

Document kernel version that integrates this overlay and where to get update instructions.

Note

To utilize the overlay with these instructions, make sure to have TBD version of kernel, modules and firmware installed. Use uname -a to determine the currently running kernel version. See TBD for information on how to update.

Apply overlay to disable mikrobus0 instance.

echo "    fdtoverlays /overlays/k3-am625-beagleplay-release-mikrobus.dtbo" | sudo tee -a /boot/firmware/extlinux/extlinux.conf
sudo shutdown -r now

Log back in after reboot and verify the device driver did not capture the busses.

debian@BeaglePlay:~$ ls /dev/play
grove  mikrobus  qwiic
debian@BeaglePlay:~$ ls /dev/play/mikrobus/
i2c
debian@BeaglePlay:~$ ls /sys/bus/mikrobus/devices/
debian@BeaglePlay:~$ ls /proc/device-tree/chosen/overlays/
k3-am625-beagleplay-release-mikrobus  name
debian@BeaglePlay:~$

To re-enable.

sudo sed -e '/release-mikrobus/ s/^#*/#/' -i /boot/firmware/extlinux/extlinux.conf
sudo shutdown -r now

Verify driver is enabled again.

debian@BeaglePlay:~$ ls /sys/bus/mikrobus/devices/
mikrobus-0
debian@BeaglePlay:~$ ls /proc/device-tree/chosen/overlays/
ls: cannot access '/proc/device-tree/chosen/overlays/': No such file or directory
debian@BeaglePlay:~$

Todo

  • How do turn off the driver?

  • How do turn on spidev?

  • How do I enable GPIO?

  • How do a provide a manifest?

Todo

  • Needs udev

  • Needs live description

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