MQTT - IO-4 Bricklet

This is the description of the MQTT API bindings for the IO-4 Bricklet. General information and technical specifications for the IO-4 Bricklet are summarized in its hardware description.

An installation guide for the MQTT API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Input

Download (example-input.txt)

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# Change XYZ to the UID of your IO-4 Bricklet

setup:
    # Get current value as bitmask
    subscribe to tinkerforge/response/io4_bricklet/XYZ/get_value
    publish '' to tinkerforge/request/io4_bricklet/XYZ/get_value

Output

Download (example-output.txt)

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# Change XYZ to the UID of your IO-4 Bricklet

setup:
    # Set pin 1 to output low: 1 << 1 = 2
    publish '{"selection_mask": 2, "direction": "out", "value": false}' to tinkerforge/request/io4_bricklet/XYZ/set_configuration 
    
    # Set pin 2 and 3 to output high: (1 << 2) | (1 << 3) = 12
    publish '{"selection_mask": 12, "direction": "out", "value": true}' to tinkerforge/request/io4_bricklet/XYZ/set_configuration 

Interrupt

Download (example-interrupt.txt)

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# Change XYZ to the UID of your IO-4 Bricklet

setup:
    # Handle incoming interrupt callbacks
    subscribe to tinkerforge/callback/io4_bricklet/XYZ/interrupt
    publish '{"register": true}' to tinkerforge/register/io4_bricklet/XYZ/interrupt # Register interrupt callback
    
    # Enable interrupt on pin 0: 1 << 0 = 1
    publish '{"interrupt_mask": 1}' to tinkerforge/request/io4_bricklet/XYZ/set_interrupt 

API

All published payloads to and from the MQTT bindings are in JSON format.

If an error occures, the bindings publish a JSON object containing the error message as attribute "_ERROR". It is published on the corresponding response topic: .../response/... for .../request/... and .../callback/... for .../register/....

Basic Functions

request/io4_bricklet/<UID>/set_value
Request payload:
  • value_mask -- int

Sets the output value (high or low) with a bitmask (4bit). A 1 in the bitmask means high and a 0 in the bitmask means low.

For example: The value 3 or 0b0011 will turn the pins 0-1 high and the pins 2-3 low.

All running monoflop timers will be aborted if this function is called.

Note

This function does nothing for pins that are configured as input. Pull-up resistors can be switched on with request/io4_bricklet/<UID>/set_configuration.

request/io4_bricklet/<UID>/get_value
Response payload:
  • value_mask -- int

Returns a bitmask of the values that are currently measured. This function works if the pin is configured to input as well as if it is configured to output.

request/io4_bricklet/<UID>/set_configuration
Request payload:
  • selection_mask -- int
  • direction -- char (has symbols)
  • value -- bool

Configures the value and direction of the specified pins. Possible directions are 'i' and 'o' for input and output.

If the direction is configured as output, the value is either high or low (set as true or false).

If the direction is configured as input, the value is either pull-up or default (set as true or false).

For example:

  • (15, 'i', true) or (0b1111, 'i', true) will set all pins of as input pull-up.
  • (8, 'i', false) or (0b1000, 'i', false) will set pin 3 of as input default (floating if nothing is connected).
  • (3, 'o', false) or (0b0011, 'o', false) will set pins 0 and 1 as output low.
  • (4, 'o', true) or (0b0100, 'o', true) will set pin 2 of as output high.

Running monoflop timers for the specified pins will be aborted if this function is called.

The default configuration is input with pull-up.

The following symbols are available for this function:

for direction:

  • "In" = 'i'
  • "Out" = 'o'
request/io4_bricklet/<UID>/get_configuration
Response payload:
  • direction_mask -- int
  • value_mask -- int

Returns a value bitmask and a direction bitmask. A 1 in the direction bitmask means input and a 0 in the bitmask means output.

For example: A return value of (3, 5) or (0b0011, 0b0101) for direction and value means that:

  • pin 0 is configured as input pull-up,
  • pin 1 is configured as input default,
  • pin 2 is configured as output high and
  • pin 3 is are configured as output low.
request/io4_bricklet/<UID>/get_edge_count
Request payload:
  • pin -- int
  • reset_counter -- bool
Response payload:
  • count -- int

Returns the current value of the edge counter for the selected pin. You can configure the edges that are counted with request/io4_bricklet/<UID>/set_edge_count_config.

If you set the reset counter to true, the count is set back to 0 directly after it is read.

New in version 2.0.1 (Plugin).

Advanced Functions

request/io4_bricklet/<UID>/set_monoflop
Request payload:
  • selection_mask -- int
  • value_mask -- int
  • time -- int

Configures a monoflop of the pins specified by the first parameter as 4 bit long bitmask. The specified pins must be configured for output. Non-output pins will be ignored.

The second parameter is a bitmask with the desired value of the specified output pins. A 1 in the bitmask means high and a 0 in the bitmask means low.

The third parameter indicates the time (in ms) that the pins should hold the value.

If this function is called with the parameters (9, 1, 1500) or (0b1001, 0b0001, 1500): Pin 0 will get high and pin 3 will get low. In 1.5s pin 0 will get low and pin 3 will get high again.

A monoflop can be used as a fail-safe mechanism. For example: Lets assume you have a RS485 bus and an IO-4 Bricklet connected to one of the slave stacks. You can now call this function every second, with a time parameter of two seconds and pin 0 set to high. Pin 0 will be high all the time. If now the RS485 connection is lost, then pin 0 will get low in at most two seconds.

request/io4_bricklet/<UID>/get_monoflop
Request payload:
  • pin -- int
Response payload:
  • value -- int
  • time -- int
  • time_remaining -- int

Returns (for the given pin) the current value and the time as set by request/io4_bricklet/<UID>/set_monoflop as well as the remaining time until the value flips.

If the timer is not running currently, the remaining time will be returned as 0.

request/io4_bricklet/<UID>/set_selected_values
Request payload:
  • selection_mask -- int
  • value_mask -- int

Sets the output value (high or low) with a bitmask, according to the selection mask. The bitmask is 4 bit long, true refers to high and false refers to low.

For example: The parameters (9, 4) or (0b0110, 0b0100) will turn pin 1 low and pin 2 high, pin 0 and 3 will remain untouched.

Running monoflop timers for the selected pins will be aborted if this function is called.

Note

This function does nothing for pins that are configured as input. Pull-up resistors can be switched on with request/io4_bricklet/<UID>/set_configuration.

request/io4_bricklet/<UID>/set_edge_count_config
Request payload:
  • selection_mask -- int
  • edge_type -- int (has symbols)
  • debounce -- int

Configures the edge counter for the selected pins.

The edge type parameter configures if rising edges, falling edges or both are counted if the pin is configured for input. Possible edge types are:

  • 0 = rising (default)
  • 1 = falling
  • 2 = both

The debounce time is given in ms.

Configuring an edge counter resets its value to 0.

If you don't know what any of this means, just leave it at default. The default configuration is very likely OK for you.

Default values: 0 (edge type) and 100ms (debounce time)

The following symbols are available for this function:

for edge_type:

  • "Rising" = 0
  • "Falling" = 1
  • "Both" = 2

New in version 2.0.1 (Plugin).

request/io4_bricklet/<UID>/get_edge_count_config
Request payload:
  • pin -- int
Response payload:
  • edge_type -- int (has symbols)
  • debounce -- int

Returns the edge type and debounce time for the selected pin as set by request/io4_bricklet/<UID>/set_edge_count_config.

The following symbols are available for this function:

for edge_type:

  • "Rising" = 0
  • "Falling" = 1
  • "Both" = 2

New in version 2.0.1 (Plugin).

request/io4_bricklet/<UID>/get_identity
Response payload:
  • uid -- string
  • connected_uid -- string
  • position -- char
  • hardware_version -- [int,int,int]
  • firmware_version -- [int,int,int]
  • device_identifier -- int (has symbols)
  • _display_name -- string

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c' or 'd'.

The device identifier numbers can be found here. If symbolic output is not disabled, the device identifier is mapped to the corresponding name in the format used in topics.

The display name contains the IO-4's name in a human readable form.

Callback Configuration Functions

request/io4_bricklet/<UID>/set_debounce_period
Request payload:
  • debounce -- int

Sets the debounce period of the register/io4_bricklet/<UID>/interrupt callback in ms.

For example: If you set this value to 100, you will get the interrupt maximal every 100ms. This is necessary if something that bounces is connected to the IO-4 Bricklet, such as a button.

The default value is 100.

request/io4_bricklet/<UID>/get_debounce_period
Response payload:
  • debounce -- int

Returns the debounce period as set by request/io4_bricklet/<UID>/set_debounce_period.

request/io4_bricklet/<UID>/set_interrupt
Request payload:
  • interrupt_mask -- int

Sets the pins on which an interrupt is activated with a bitmask. Interrupts are triggered on changes of the voltage level of the pin, i.e. changes from high to low and low to high.

For example: An interrupt bitmask of 10 or 0b1010 will enable the interrupt for pins 1 and 3.

The interrupt is delivered with the register/io4_bricklet/<UID>/interrupt callback.

request/io4_bricklet/<UID>/get_interrupt
Response payload:
  • interrupt_mask -- int

Returns the interrupt bitmask as set by request/io4_bricklet/<UID>/set_interrupt.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the corresponding .../register/... topic and an optional suffix. This suffix can be used to deregister the callback later.

Note

Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

register/io4_bricklet/<UID>/interrupt
Request payload:
  • register -- bool
Response payload:
  • interrupt_mask -- int
  • value_mask -- int

A callback can be registered for this event by publishing to the .../register/io4_bricklet/<UID>/interrupt[/<SUFFIX>] topic with the payload "true". An added callback can be removed by publishing to the same topic with the payload "false". To support multiple (de)registrations, e.g. for message filtering, an optional suffix can be used.

If the callback is triggered, a message with it's payload is published under the corresponding .../callback/io4_bricklet/<UID>/interrupt[/<SUFFIX>] topic for each registered suffix.

This callback is triggered whenever a change of the voltage level is detected on pins where the interrupt was activated with request/io4_bricklet/<UID>/set_interrupt.

The values are a bitmask that specifies which interrupts occurred and the current value bitmask.

For example:

  • (1, 1) or (0b0001, 0b0001) means that an interrupt on pin 0 occurred and currently pin 0 is high and pins 1-3 are low.
  • (9, 14) or (0b1001, 0b1110) means that interrupts on pins 0 and 3 occurred and currently pin 0 is low and pins 1-3 are high.
register/io4_bricklet/<UID>/monoflop_done
Request payload:
  • register -- bool
Response payload:
  • selection_mask -- int
  • value_mask -- int

A callback can be registered for this event by publishing to the .../register/io4_bricklet/<UID>/monoflop_done[/<SUFFIX>] topic with the payload "true". An added callback can be removed by publishing to the same topic with the payload "false". To support multiple (de)registrations, e.g. for message filtering, an optional suffix can be used.

If the callback is triggered, a message with it's payload is published under the corresponding .../callback/io4_bricklet/<UID>/monoflop_done[/<SUFFIX>] topic for each registered suffix.

This callback is triggered whenever a monoflop timer reaches 0. The callback payload members contain the involved pins and the current value of the pins (the value after the monoflop).