MQTT - RS232 Bricklet 2.0

This is the description of the MQTT API bindings for the RS232 Bricklet 2.0. General information and technical specifications for the RS232 Bricklet 2.0 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).

Loopback

Download (example-loopback.txt)

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# For this example connect the RX pin to the TX pin on the same Bricklet

# Change XYZ to the UID of your RS232 Bricklet 2.0

setup:
    # Handle incoming read callbacks
    subscribe to tinkerforge/callback/rs232_v2_bricklet/XYZ/read # Received messages contain the message as string
    publish '{"register": true}' to tinkerforge/register/rs232_v2_bricklet/XYZ/read # Register read callback
    
    # Enable read callback
    publish '' to tinkerforge/request/rs232_v2_bricklet/XYZ/enable_read_callback 
    
    # Write "test" string
    publish '{"message": "test"}' to tinkerforge/request/rs232_v2_bricklet/XYZ/write 

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/rs232_v2_bricklet/<UID>/write
Request payload:
 
  • message -- string
Response payload:
 
  • message_written -- int

Writes characters to the RS232 interface. The characters can be binary data, ASCII or similar is not necessary.

The return value is the number of characters that were written.

See request/rs232_v2_bricklet/<UID>/set_configuration for configuration possibilities regarding baud rate, parity and so on.

request/rs232_v2_bricklet/<UID>/read
Request payload:
 
  • length -- int
Response payload:
 
  • message -- string

Returns up to length characters from receive buffer.

Instead of polling with this function, you can also use callbacks. But note that this function will return available data only when the read callback is disabled. See request/rs232_v2_bricklet/<UID>/enable_read_callback and register/rs232_v2_bricklet/<UID>/read callback.

request/rs232_v2_bricklet/<UID>/set_configuration
Request payload:
 
  • baudrate -- int
  • parity -- int (has symbols)
  • stopbits -- int (has symbols)
  • wordlength -- int (has symbols)
  • flowcontrol -- int (has symbols)

Sets the configuration for the RS232 communication. Available options:

  • Baud rate between 100 and 2000000 baud.
  • Parity of none, odd or even.
  • Stop bits can be 1 or 2.
  • Word length of 5 to 8.
  • Flow control can be off, software or hardware.

The default is: 115200 baud, parity none, 1 stop bit, word length 8.

The following symbols are available for this function:

for parity:

  • "None" = 0
  • "Odd" = 1
  • "Even" = 2

for stopbits:

  • "1" = 1
  • "2" = 2

for wordlength:

  • "5" = 5
  • "6" = 6
  • "7" = 7
  • "8" = 8

for flowcontrol:

  • "Off" = 0
  • "Software" = 1
  • "Hardware" = 2
request/rs232_v2_bricklet/<UID>/get_configuration
Response payload:
 
  • baudrate -- int
  • parity -- int (has symbols)
  • stopbits -- int (has symbols)
  • wordlength -- int (has symbols)
  • flowcontrol -- int (has symbols)

Returns the configuration as set by request/rs232_v2_bricklet/<UID>/set_configuration.

The following symbols are available for this function:

for parity:

  • "None" = 0
  • "Odd" = 1
  • "Even" = 2

for stopbits:

  • "1" = 1
  • "2" = 2

for wordlength:

  • "5" = 5
  • "6" = 6
  • "7" = 7
  • "8" = 8

for flowcontrol:

  • "Off" = 0
  • "Software" = 1
  • "Hardware" = 2

Advanced Functions

request/rs232_v2_bricklet/<UID>/set_buffer_config
Request payload:
 
  • send_buffer_size -- int
  • receive_buffer_size -- int

Sets the send and receive buffer size in byte. In total the buffers have to be 10240 byte (10kb) in size, the minimum buffer size is 1024 byte (1kb) for each.

The current buffer content is lost if this function is called.

The send buffer holds data that is given by request/rs232_v2_bricklet/<UID>/write and can not be written yet. The receive buffer holds data that is received through RS232 but could not yet be send to the user, either by request/rs232_v2_bricklet/<UID>/read or through register/rs232_v2_bricklet/<UID>/read callback.

The default configuration is 5120 byte (5kb) per buffer.

request/rs232_v2_bricklet/<UID>/get_buffer_config
Response payload:
 
  • send_buffer_size -- int
  • receive_buffer_size -- int

Returns the buffer configuration as set by request/rs232_v2_bricklet/<UID>/set_buffer_config.

request/rs232_v2_bricklet/<UID>/get_buffer_status
Response payload:
 
  • send_buffer_used -- int
  • receive_buffer_used -- int

Returns the currently used bytes for the send and received buffer.

See request/rs232_v2_bricklet/<UID>/set_buffer_config for buffer size configuration.

request/rs232_v2_bricklet/<UID>/get_error_count
Response payload:
 
  • error_count_overrun -- int
  • error_count_parity -- int

Returns the current number of overrun and parity errors.

request/rs232_v2_bricklet/<UID>/get_spitfp_error_count
Response payload:
 
  • error_count_ack_checksum -- int
  • error_count_message_checksum -- int
  • error_count_frame -- int
  • error_count_overflow -- int

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.

request/rs232_v2_bricklet/<UID>/set_bootloader_mode
Request payload:
 
  • mode -- int (has symbols)
Response payload:
 
  • status -- int (has symbols)

Sets the bootloader mode and returns the status after the requested mode change was instigated.

You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

The following symbols are available for this function:

for mode:

  • "Bootloader" = 0
  • "Firmware" = 1
  • "BootloaderWaitForReboot" = 2
  • "FirmwareWaitForReboot" = 3
  • "FirmwareWaitForEraseAndReboot" = 4

for status:

  • "OK" = 0
  • "InvalidMode" = 1
  • "NoChange" = 2
  • "EntryFunctionNotPresent" = 3
  • "DeviceIdentifierIncorrect" = 4
  • "CRCMismatch" = 5
request/rs232_v2_bricklet/<UID>/get_bootloader_mode
Response payload:
 
  • mode -- int (has symbols)

Returns the current bootloader mode, see request/rs232_v2_bricklet/<UID>/set_bootloader_mode.

The following symbols are available for this function:

for mode:

  • "Bootloader" = 0
  • "Firmware" = 1
  • "BootloaderWaitForReboot" = 2
  • "FirmwareWaitForReboot" = 3
  • "FirmwareWaitForEraseAndReboot" = 4
request/rs232_v2_bricklet/<UID>/set_write_firmware_pointer
Request payload:
 
  • pointer -- int

Sets the firmware pointer for request/rs232_v2_bricklet/<UID>/write_firmware. The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

request/rs232_v2_bricklet/<UID>/write_firmware
Request payload:
 
  • data -- [int,... (x64)]
Response payload:
 
  • status -- int

Writes 64 Bytes of firmware at the position as written by request/rs232_v2_bricklet/<UID>/set_write_firmware_pointer before. The firmware is written to flash every 4 chunks.

You can only write firmware in bootloader mode.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

request/rs232_v2_bricklet/<UID>/set_status_led_config
Request payload:
 
  • config -- int (has symbols)

Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.

The following symbols are available for this function:

for config:

  • "Off" = 0
  • "On" = 1
  • "ShowHeartbeat" = 2
  • "ShowStatus" = 3
request/rs232_v2_bricklet/<UID>/get_status_led_config
Response payload:
 
  • config -- int (has symbols)

Returns the configuration as set by request/rs232_v2_bricklet/<UID>/set_status_led_config

The following symbols are available for this function:

for config:

  • "Off" = 0
  • "On" = 1
  • "ShowHeartbeat" = 2
  • "ShowStatus" = 3
request/rs232_v2_bricklet/<UID>/get_chip_temperature
Response payload:
 
  • temperature -- int

Returns the temperature in °C as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has bad accuracy. Practically it is only useful as an indicator for temperature changes.

request/rs232_v2_bricklet/<UID>/reset

Calling this function will reset the Bricklet. All configurations will be lost.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

request/rs232_v2_bricklet/<UID>/write_uid
Request payload:
 
  • uid -- int

Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.

We recommend that you use Brick Viewer to change the UID.

request/rs232_v2_bricklet/<UID>/read_uid
Response payload:
 
  • uid -- int

Returns the current UID as an integer. Encode as Base58 to get the usual string version.

request/rs232_v2_bricklet/<UID>/get_identity
Response payload:
 
  • uid -- string
  • connected_uid -- string
  • position -- string
  • 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 RS232 2.0's name in a human readable form.

Callback Configuration Functions

request/rs232_v2_bricklet/<UID>/enable_read_callback

Enables the register/rs232_v2_bricklet/<UID>/read callback.

By default the callback is disabled.

request/rs232_v2_bricklet/<UID>/disable_read_callback

Disables the register/rs232_v2_bricklet/<UID>/read callback.

By default the callback is disabled.

request/rs232_v2_bricklet/<UID>/is_read_callback_enabled
Response payload:
 
  • enabled -- bool

Returns true if the register/rs232_v2_bricklet/<UID>/read callback is enabled, false otherwise.

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/rs232_v2_bricklet/<UID>/read
Request payload:
 
  • register -- bool
Response payload:
 
  • message -- string

A callback can be registered for this event by publishing to the .../register/rs232_v2_bricklet/<UID>/read[/<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/rs232_v2_bricklet/<UID>/read[/<SUFFIX>] topic for each registered suffix.

This callback is called if new data is available.

To enable this callback, use request/rs232_v2_bricklet/<UID>/enable_read_callback.

register/rs232_v2_bricklet/<UID>/error_count
Request payload:
 
  • register -- bool
Response payload:
 
  • error_count_overrun -- int
  • error_count_parity -- int

A callback can be registered for this event by publishing to the .../register/rs232_v2_bricklet/<UID>/error_count[/<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/rs232_v2_bricklet/<UID>/error_count[/<SUFFIX>] topic for each registered suffix.

This callback is called if a new error occurs. It returns the current overrun and parity error count.