Voxl-IO questions (GPIO & i2c)

  • I have a few questions about the voxl-io library, and I would love if you could help me:

    1.1. Missing ability to GPIO interrupt (or missing documentation?)
    1.2. Missing ability to control of Pull Up/Down (Is the hardware exist to do so?, or missing documentation?)
    1.3. Need clarification in the i2c api, can I write to a device without specifying a designated register?
    	For example in the smbus linux library: (https://www.kernel.org/doc/html/latest/i2c/smbus-protocol.html)
    		i2c_smbus_write_byte(...): Writes a single byte to a device
    		i2c_smbus_write_byte_data(...): Writes a single byte to a designated register on the device

  • Dev Team

    Hi @amitmol ,

    The VOXL is based on the snapdragon 820, built for smart phones, and has a bit less control than a microcontroller with configurability....

    • Interrupt- not out of the box as far as I know
    • pull up/down - this is a device tree modification likely, not something quick
    • on this platform, we use voxl-io to send/receive the I2C commands to the sDSP, so it's what's exposed there presently only unless it's added later

  • Dev Team

    We have example Python code in voxl-modem to control the B2B GPIO

    ## All GPIO pins need to be exported before they can be used
    def gpio_export(num):
        subprocess.call("echo " + num + " > /sys/class/gpio/export",
                        stderr=FNULL, shell=True)
    ## Each GPIO has to have its direction set prior to use
    # @param num  pin number
    # @param direction 'in' or 'out'
    def gpio_direction_map(num, direction):
        subprocess.call("echo " + direction + " > /sys/class/gpio/gpio" \
                        + num + "/direction",
                        stderr=FNULL, shell=True)
    ## Set a value to an 'out' gpio
    def set_gpio(num, value):
        subprocess.call("echo " + value + " > /sys/class/gpio/gpio" + num + "/value",
                        stderr=FNULL, shell=True)
    ##  Reads a GPIO pin
    #   @apram pin
    #       pin number
    #   @return
    #       integer value [0,1]
    def gpio_read_int(pin_int):
        gpio_file = '/sys/class/gpio/gpio' + str(pin_int) + '/value'
        value = subprocess.check_output(['cat', gpio_file]).strip()
        return int(value)

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