Shell - Hall Effect Bricklet – Tinkerforge

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# Shell - Hall Effect Bricklet

This is the description of the Shell API bindings for the Hall Effect Bricklet. General information and technical specifications for the Hall Effect Bricklet are summarized in its hardware description.

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

## Examples

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

### Simple

Download (example-simple.sh)

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    #!/bin/sh
    # connects to localhost:4223 by default, use --host and --port to change it

    # change to your UID
    uid=XYZ

    # get current edge count without reset
    tinkerforge call hall-effect-bricklet $uid get-edge-count false

### Callback

Download (example-callback.sh)

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    #!/bin/sh
    # connects to localhost:4223 by default, use --host and --port to change it

    # change to your UID
    uid=XYZ

    # set period for edge_count callback to 0.05s (50ms)
    # note: the edge_count callback is only called every second if the
    #       edge_count has changed since the last call!
    tinkerforge call hall-effect-bricklet $uid set-edge-count-callback-period 50

    # handle incoming edge count callbacks
    tinkerforge dispatch hall-effect-bricklet $uid edge-count

## API

Possible exit codes for all `tinkerforge` commands are:

- 1: interrupted (ctrl+c)
- 2: syntax error
- 21: Python 2.5 or newer is required
- 22: Python `argparse` module is missing
- 23: socket error
- 24: other exception
- 25: invalid placeholder in format string
- 26: authentication error
- 201: timeout occurred
- 209: invalid argument value
- 210: function is not supported
- 211: unknown error

### Command Structure

The common options of the `call` and `dispatch` commands are documented here. The specific command structure is shown below.

tinkerforge `call` `hall-effect-bricklet` [<option>..] <uid> <function> [<argument>..]

  Parameters:

  - <uid> -- string
  - <function> -- string

  The `call` command is used to call a function of the Hall Effect Bricklet. It can take several options:

  - `--help` shows help for the specific `call` command and exits
  - `--list-functions` shows a list of known functions of the Hall Effect Bricklet and exits

tinkerforge `dispatch` `hall-effect-bricklet` [<option>..] <uid> <callback>

  Parameters:

  - <uid> -- string
  - <callback> -- string

  The `dispatch` command is used to dispatch a callback of the Hall Effect Bricklet. It can take several options:

  - `--help` shows help for the specific `dispatch` command and exits
  - `--list-callbacks` shows a list of known callbacks of the Hall Effect Bricklet and exits

tinkerforge call `hall-effect-bricklet` <uid> `<function>` [<option>..] [<argument>..]

  Parameters:

  - <uid> -- string
  - <function> -- string

  The `<function>` to be called can take different options depending of its kind. All functions can take the following options:

  - `--help` shows help for the specific function and exits

  Getter functions can take the following options:

  - `--execute <command>` shell command line to execute for each incoming response (see section about output formatting for details)

  Setter functions can take the following options:

  - `--expect-response` requests response and waits for it

  The `--expect-response` option for setter functions allows to detect timeouts and other error conditions calls of setters as well. The device will then send a response for this purpose. If this option is not given for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

tinkerforge dispatch `hall-effect-bricklet` <uid> `<callback>` [<option>..]

  Parameters:

  - <uid> -- string
  - <callback> -- string

  The `<callback>` to be dispatched can take several options:

  - `--help` shows help for the specific callback and exits
  - `--execute <command>` shell command line to execute for each incoming response (see section about output formatting for details)

### Basic Functions

tinkerforge call `hall-effect-bricklet` <uid> `get-value`

  Output:

  - value -- bool

  Returns true if a magnetic field of 35 Gauss (3.5mT) or greater is detected.

tinkerforge call `hall-effect-bricklet` <uid> `get-edge-count` <reset-counter>

  Parameters:

  - <reset-counter> -- bool

  Output:

  - count -- int

  Returns the current value of the edge counter. You can configure edge type (rising, falling, both) that is counted with `set-edge-count-config`.

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

### Advanced Functions

tinkerforge call `hall-effect-bricklet` <uid> `set-edge-count-config` <edge-type> <debounce>

  Parameters:

  - <edge-type> -- int (has symbols)
  - <debounce> -- int

  Output: | no output

  The edge type parameter configures if rising edges, falling edges or both are counted. Possible edge types are:

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

  A magnetic field of 35 Gauss (3.5mT) or greater causes a falling edge and a magnetic field of 25 Gauss (2.5mT) or smaller causes a rising edge.

  If a magnet comes near the Bricklet the signal goes low (falling edge), if a magnet is removed from the vicinity the signal goes high (rising edge).

  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:

  - `rising` = 0, for <edge-type>
  - `falling` = 1, for <edge-type>
  - `both` = 2, for <edge-type>

tinkerforge call `hall-effect-bricklet` <uid> `get-edge-count-config`

  Output:

  - edge-type -- int (has symbols)
  - debounce -- int

  Returns the edge type and debounce time as set by `set-edge-count-config`.

  The following symbols are available for this function:

  - `rising` = 0, for edge-type
  - `falling` = 1, for edge-type
  - `both` = 2, for edge-type

tinkerforge call `hall-effect-bricklet` <uid> `get-identity`

  Output:

  - uid -- string
  - connected-uid -- string
  - position -- char
  - hardware-version -- int,int,int
  - firmware-version -- int,int,int
  - device-identifier -- int (has symbols)

  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.

### Callback Configuration Functions

tinkerforge call `hall-effect-bricklet` <uid> `set-edge-interrupt` <edges>

  Parameters:

  - <edges> -- int

  Output: | no output

  Sets the number of edges until an interrupt is invoked.

  If edges is set to n, an interrupt is invoked for every n-th detected edge.

  If edges is set to 0, the interrupt is disabled.

  Default value is 0.

tinkerforge call `hall-effect-bricklet` <uid> `get-edge-interrupt`

  Output:

  - edges -- int

  Returns the edges as set by `set-edge-interrupt`.

tinkerforge call `hall-effect-bricklet` <uid> `set-edge-count-callback-period` <period>

  Parameters:

  - <period> -- int

  Output: | no output

  Sets the period in ms with which the `edge-count` callback is triggered periodically. A value of 0 turns the callback off.

  `edge-count` is only triggered if the edge count has changed since the last triggering.

  The default value is 0.

tinkerforge call `hall-effect-bricklet` <uid> `get-edge-count-callback-period`

  Output:

  - period -- int

  Returns the period as set by `set-edge-count-callback-period`.

### Callbacks

Callbacks can be used to receive time critical or recurring data from the device:

    tinkerforge dispatch hall-effect-bricklet <uid> example

The available callbacks are described below.

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.

tinkerforge dispatch `hall-effect-bricklet` <uid> `edge-count`

  Output:

  - count -- int
  - value -- bool

  This callback is triggered periodically with the period that is set by `set-edge-count-callback-period`. The parameters are the current count and the current value (see `get-value` and `get-edge-count`).

  `edge-count` is only triggered if the count or value changed since the last triggering.

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