Software / API Bindings / MQTT / API Reference and Examples / Bricklets / One Wire Bricklet

MQTT - One Wire Bricklet¶

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

Read Ds18b20 Temperature¶

Download (example-read-ds18b20-temperature.txt)

# Change XYZ to the UID of your One Wire Bricklet

setup:
    publish '{"identifier": 0, "command": 78}' to tinkerforge/request/one_wire_bricklet/XYZ/write_command # WRITE SCRATCHPAD

    publish '{"data": 0}' to tinkerforge/request/one_wire_bricklet/XYZ/write # ALARM H (unused)

    publish '{"data": 0}' to tinkerforge/request/one_wire_bricklet/XYZ/write # ALARM L (unused)

    publish '{"data": 127}' to tinkerforge/request/one_wire_bricklet/XYZ/write # CONFIGURATION: 12-bit mode

    # Read temperature 10 times
    for i in 0..9

        publish '{"identifier": 0, "command": 68}' to tinkerforge/request/one_wire_bricklet/XYZ/write_command # CONVERT T (start temperature conversion)

        wait for 1s # Wait for conversion to finish

        publish '{"identifier": 0, "command": 190}' to tinkerforge/request/one_wire_bricklet/XYZ/write_command # READ SCRATCHPAD

        subscribe to tinkerforge/response/one_wire_bricklet/XYZ/read # Subscribe to responses for read commands below
            first message is t_low
            second message is t_high
        endsubscribe

        publish '' to tinkerforge/request/one_wire_bricklet/XYZ/read # Read t_low
        publish '' to tinkerforge/request/one_wire_bricklet/XYZ/read # Read t_high

        set temperature to t_low | (t_high << 8)
        if temperature > (1 << 12)
            set temperature to temperature - (1 << 16) # Negative 12-bit values are sign-extended to 16-bit two's complement.
        endif

        set temperature to temperature / 16 # 12 bit mode measures in units of 1/16°C.
        print temperature

    endfor

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 member _ERROR. It is published on the corresponding response topic: .../response/... for .../request/... and .../callback/... for .../register/....

Basic Functions¶

request/one_wire_bricklet/<UID>/search_bus¶

Request:	empty payload
Response:	identifier – Type: [int, ...], Length: variable, Range: [0 to 2⁶⁴ - 1] status – Type: int, Range: See symbols

Returns a list of up to 64 identifiers of the connected 1-Wire devices. Each identifier is 64-bit and consists of 8-bit family code, 48-bit ID and 8-bit CRC.

To get these identifiers the Bricklet runs the SEARCH ROM algorithm, as defined by Maxim.

The following symbols are available for this function:

For status:

"ok" = 0
"busy" = 1
"no_presence" = 2
"timeout" = 3
"error" = 4

request/one_wire_bricklet/<UID>/reset_bus¶

Request:	empty payload
Response:	status – Type: int, Range: See symbols

Resets the bus with the 1-Wire reset operation.

The following symbols are available for this function:

For status:

"ok" = 0
"busy" = 1
"no_presence" = 2
"timeout" = 3
"error" = 4

request/one_wire_bricklet/<UID>/write¶

Request:	data – Type: int, Range: [0 to 255]
Response:	status – Type: int, Range: See symbols

Writes a byte of data to the 1-Wire bus.

The following symbols are available for this function:

For status:

"ok" = 0
"busy" = 1
"no_presence" = 2
"timeout" = 3
"error" = 4

request/one_wire_bricklet/<UID>/read¶

Request:	empty payload
Response:	data – Type: int, Range: [0 to 255] status – Type: int, Range: See symbols

Reads a byte of data from the 1-Wire bus.

The following symbols are available for this function:

For status:

"ok" = 0
"busy" = 1
"no_presence" = 2
"timeout" = 3
"error" = 4

request/one_wire_bricklet/<UID>/write_command¶

Request:	identifier – Type: int, Range: [0 to 2⁶⁴ - 1] command – Type: int, Range: [0 to 255]
Response:	status – Type: int, Range: See symbols

Writes a command to the 1-Wire device with the given identifier. You can obtain the identifier by calling request/one_wire_bricklet/<UID>/search_bus. The MATCH ROM operation is used to write the command.

If you only have one device connected or want to broadcast to all devices you can set the identifier to 0. In this case the SKIP ROM operation is used to write the command.

The following symbols are available for this function:

For status:

"ok" = 0
"busy" = 1
"no_presence" = 2
"timeout" = 3
"error" = 4

Advanced Functions¶

request/one_wire_bricklet/<UID>/set_communication_led_config¶

Request:	config – Type: int, Range: See symbols, Default: 3
Response:	no response

Sets the communication LED configuration. By default the LED shows 1-wire communication traffic by flickering.

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

If the Bricklet is in bootloader mode, the LED is off.

The following symbols are available for this function:

For config:

"off" = 0
"on" = 1
"show_heartbeat" = 2
"show_communication" = 3

request/one_wire_bricklet/<UID>/get_communication_led_config¶

Request:	empty payload
Response:	config – Type: int, Range: See symbols, Default: 3

Returns the configuration as set by request/one_wire_bricklet/<UID>/set_communication_led_config

The following symbols are available for this function:

For config:

"off" = 0
"on" = 1
"show_heartbeat" = 2
"show_communication" = 3

request/one_wire_bricklet/<UID>/get_spitfp_error_count¶

Request:	empty payload
Response:	error_count_ack_checksum – Type: int, Range: [0 to 2³² - 1] error_count_message_checksum – Type: int, Range: [0 to 2³² - 1] error_count_frame – Type: int, Range: [0 to 2³² - 1] error_count_overflow – Type: int, Range: [0 to 2³² - 1]

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/one_wire_bricklet/<UID>/set_status_led_config¶

Request:	config – Type: int, Range: See symbols, Default: 3
Response:	no response

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
"show_heartbeat" = 2
"show_status" = 3

request/one_wire_bricklet/<UID>/get_status_led_config¶

Request:	empty payload
Response:	config – Type: int, Range: See symbols, Default: 3

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

The following symbols are available for this function:

For config:

"off" = 0
"on" = 1
"show_heartbeat" = 2
"show_status" = 3

request/one_wire_bricklet/<UID>/get_chip_temperature¶

Request:	empty payload
Response:	temperature – Type: int, Unit: 1 °C, Range: [-2¹⁵ to 2¹⁵ - 1]

Returns the temperature 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/one_wire_bricklet/<UID>/reset¶

Request:	empty payload
Response:	no response

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/one_wire_bricklet/<UID>/get_identity¶

Request:

empty payload

Response:

uid – Type: string, Length: up to 8
connected_uid – Type: string, Length: up to 8
position – Type: char, Range: ["a" to "h", "z"]
hardware_version – Type: [int, ...], Length: 3

0: major – Type: int, Range: [0 to 255]
1: minor – Type: int, Range: [0 to 255]
2: revision – Type: int, Range: [0 to 255]

firmware_version – Type: [int, ...], Length: 3

0: major – Type: int, Range: [0 to 255]
1: minor – Type: int, Range: [0 to 255]
2: revision – Type: int, Range: [0 to 255]

device_identifier – Type: int, Range: [0 to 2¹⁶ - 1]
_display_name – Type: 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', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). A Bricklet connected to an Isolator Bricklet is always at position 'z'.

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 One Wire's name in a human readable form.

Internal Functions¶

Internal functions are used for maintenance tasks such as flashing a new firmware of changing the UID of a Bricklet. These task should be performed using Brick Viewer instead of using the internal functions directly.

request/one_wire_bricklet/<UID>/set_bootloader_mode¶

Request:	mode – Type: int, Range: See symbols
Response:	status – Type: int, Range: See 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
"bootloader_wait_for_reboot" = 2
"firmware_wait_for_reboot" = 3
"firmware_wait_for_erase_and_reboot" = 4

For status:

"ok" = 0
"invalid_mode" = 1
"no_change" = 2
"entry_function_not_present" = 3
"device_identifier_incorrect" = 4
"crc_mismatch" = 5

request/one_wire_bricklet/<UID>/get_bootloader_mode¶

Request:	empty payload
Response:	mode – Type: int, Range: See symbols

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

The following symbols are available for this function:

For mode:

"bootloader" = 0
"firmware" = 1
"bootloader_wait_for_reboot" = 2
"firmware_wait_for_reboot" = 3
"firmware_wait_for_erase_and_reboot" = 4

request/one_wire_bricklet/<UID>/set_write_firmware_pointer¶

Request:	pointer – Type: int, Unit: 1 B, Range: [0 to 2³² - 1]
Response:	no response

Sets the firmware pointer for request/one_wire_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/one_wire_bricklet/<UID>/write_firmware¶

Request:	data – Type: [int, ...], Length: 64, Range: [0 to 255]
Response:	status – Type: int, Range: [0 to 255]

Writes 64 Bytes of firmware at the position as written by request/one_wire_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/one_wire_bricklet/<UID>/write_uid¶

Request:	uid – Type: int, Range: [0 to 2³² - 1]
Response:	no response

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/one_wire_bricklet/<UID>/read_uid¶

Request:	empty payload
Response:	uid – Type: int, Range: [0 to 2³² - 1]

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