This is the description of the Modbus protocol for the Industrial Dual 0-20mA Bricklet. General information and technical specifications for the Industrial Dual 0-20mA Bricklet are summarized in its hardware description.
A general description of the Modbus protocol structure can be found here.
Two sensors can be connected to the Bricklet. Functions that are related directly to a sensor have a sensor parameter to specify one of the two sensors. Valid values for the sensor parameter are 0 and 1.
Function ID: | 1 |
---|---|
Request: |
|
Response: |
|
Returns the current of the specified sensor (0 or 1). The value is in nA and between 0nA and 22505322nA (22.5mA).
It is possible to detect if an IEC 60381-1 compatible sensor is connected and if it works probably.
If the returned current is below 4mA, there is likely no sensor connected or the sensor may be defect. If the returned current is over 20mA, there might be a short circuit or the sensor may be defect.
If you want to get the current periodically, it is recommended to use the CALLBACK_CURRENT callback and set the period with set_current_callback_period.
Function ID: | 8 |
---|---|
Request: |
|
Response: | no response |
Sets the sample rate to either 240, 60, 15 or 4 samples per second. The resolution for the rates is 12, 14, 16 and 18 bit respectively.
Value | Description |
---|---|
0 | 240 samples per second, 12 bit resolution |
1 | 60 samples per second, 14 bit resolution |
2 | 15 samples per second, 16 bit resolution |
3 | 4 samples per second, 18 bit resolution |
The default value is 3 (4 samples per second with 18 bit resolution).
The following meanings are defined for the parameters of this function:
Function ID: | 9 |
---|---|
Request: | empty payload |
Response: |
|
Returns the sample rate as set by set_sample_rate.
The following meanings are defined for the parameters of this function:
Function ID: | 255 |
---|---|
Request: | empty payload |
Response: |
|
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.
Function ID: | 2 |
---|---|
Request: |
|
Response: | no response |
Sets the period in ms with which the CALLBACK_CURRENT callback is triggered periodically for the given sensor. A value of 0 turns the callback off.
The CALLBACK_CURRENT callback is only triggered if the current has changed since the last triggering.
The default value is 0.
Function ID: | 3 |
---|---|
Request: |
|
Response: |
|
Returns the period as set by set_current_callback_period.
Function ID: | 4 |
---|---|
Request: |
|
Response: | no response |
Sets the thresholds for the CALLBACK_CURRENT_REACHED callback for the given sensor.
The following options are possible:
Option | Description |
---|---|
'x' | Callback is turned off |
'o' | Callback is triggered when the current is outside the min and max values |
'i' | Callback is triggered when the current is inside the min and max values |
'<' | Callback is triggered when the current is smaller than the min value (max is ignored) |
'>' | Callback is triggered when the current is greater than the min value (max is ignored) |
The default value is ('x', 0, 0).
The following meanings are defined for the parameters of this function:
Function ID: | 5 |
---|---|
Request: |
|
Response: |
|
Returns the threshold as set by set_current_callback_threshold.
The following meanings are defined for the parameters of this function:
Function ID: | 6 |
---|---|
Request: |
|
Response: | no response |
Sets the period in ms with which the threshold callback
is triggered, if the threshold
keeps being reached.
The default value is 100.
Function ID: | 7 |
---|---|
Request: | empty payload |
Response: |
|
Returns the debounce period as set by set_debounce_period.
Function ID: | 10 |
---|---|
Response: |
|
This callback is triggered periodically with the period that is set by set_current_callback_period. The response value is the current of the sensor.
The CALLBACK_CURRENT callback is only triggered if the current has changed since the last triggering.
Function ID: | 11 |
---|---|
Response: |
|
This callback is triggered when the threshold as set by set_current_callback_threshold is reached. The response value is the current of the sensor.
If the threshold keeps being reached, the callback is triggered periodically with the period as set by set_debounce_period.