JSON command

By using http://brewpiless.local/testcmd.htm, you can control BrewPi core directly. For example, to set temperature to Fahrenheit. Open the testcm.htm page, and enter the following string, and send.

j{"tempFormat":"F"}

You can set multiple parameters in one command. The command after j is in formal JSON format. Please include the double quote(") for key and string value.

Key	Meaning	Note
tempFormat	Temperature format	F for Fahrenheit, C for Celius. The algorithm always uses fixed point Celcius format internally, but it converts all settings that go in or out to the right format.
tempSetMin	Minimum temperature setting	The fridge and beer temperatures cannot go below this value.
tempSetMax	Maximum temperature setting	The fridge and beer temperatures cannot go above this value.
Kp	Kp parameters of PID	The beer temperature error is multiplied by Kp to give the proportional part of the PID value.
Ki	Ki parameters of PID	When the integral is active, the error is added to the integral every 30 seconds. The result is multiplied by Ki to give the integral part.
Kd	Kd parameters of PID	The derivative of the beer temperature is multiplied by Kd to give the derivative part of the PID value.
pidMax	PID Maximum	You can define the maximum difference between the beer temp setting and fridge temp setting here. The fridge setting will be clipped to this range.
iMaxErr	Integrator: maximum temp error °C	The integral is only active when the temperature is close to the target temperature. This is the maximum error for which the integral is active.
idleRangeH	Temperature idle range top	When the fridge temperature is within this range, it won't heat or cool, regardless of other settings.
idleRangeL	Temperature idle range bottom	When the fridge temperature is within this range, it won't heat or cool, regardless of other settings.
heatTargetH	Heating target upper bound	When the overshoot lands under this value, the peak is within target range and the estimator is not adjusted.
heatTargetL	Heating target lower bound	When the overshoot lands above this value, the peak is within target range and the estimator is not adjusted.
coolTargetH	Cooling target upper bound	When the overshoot lands under this value, the peak is within target range and the estimator is not adjusted.
coolTargetL	Cooling target lower bound	When the overshoot lands above this value, the peak is within target range and the estimator is not adjusted.
maxHeatTimeForEst	Maximum time in seconds for heating overshoot estimator	The time the fridge has been heating is used to estimate overshoot. This is the maximum time that is taken into account.
maxCoolTimeForEst	Maximum time in seconds for cooling overshoot estimator	The time the fridge has been cooling is used to estimate overshoot. This is the maximum time that is taken into account.
fridgeFastFilt	Fridge fast filter delay time	The fridge fast filter is used for on-off control, display and logging. It needs to have a small delay. 0 = 9 Seconds, 1 = 18 Seconds, 2 = 39 Seconds, 3 = 78 Seconds, 4 = 159 Seconds, 5 = 318 Seconds, 6 = 639 Seconds
fridgeSlowFilt	Fridge slow filter delay time	The fridge slow filter is used for peak detection to adjust the overshoot estimators. More smoothing is needed to prevent small fluctuations to be recognized as peaks. 0 = 9 Seconds, 1 = 18 Seconds, 2 = 39 Seconds, 3 = 78 Seconds, 4 = 159 Seconds, 5 = 318 Seconds, 6 = 639 Seconds
fridgeSlopeFilt	Fridge slope filter delay time	The fridge slope filter is not used in the current version. 0 = 27 Seconds, 1 = 54 Seconds, 2 = 2 Minutes, 3 = 4 Minutes, 4 = 8 Minutes, 5 = 16 Minutes, 6 = 32 Minutes.
beerFastFilt	Beer fast filter delay time	The beer fast filter is used for display and data logging. More filtering give a smoother line, but also more delay. 0 = 9 Seconds, 1 = 18 Seconds, 2 = 39 Seconds, 3 = 78 Seconds, 4 = 159 Seconds, 5 = 318 Seconds, 6 = 639 Seconds
beerSlowFilt	Beer slow filter delay time	The beer slow filter is used for the control algorithm. The fridge temperature setting is calculated from this filter. Because a small difference in beer temperature causes a large adjustment in the fridge temperature, more smoothing is needed. 0 = 9 Seconds, 1 = 18 Seconds, 2 = 39 Seconds, 3 = 78 Seconds, 4 = 159 Seconds, 5 = 318 Seconds, 6 = 639 Seconds
beerSlopeFilt	Beer slope filter delay time	The slope is calculated every 30 seconds and fed to this filter. More filtering means a smoother fridge setting. 0 = 27 Seconds, 1 = 54 Seconds, 2 = 2 Minutes, 3 = 4 Minutes, 4 = 8 Minutes, 5 = 16 Minutes, 6 = 23 Minutes
lah	Use light as heater	If this option is set to 'Yes'the light wil be used as a heater. 0 = No, 1 = Yes
hs	Rotary encoder trigger step	When you feel like you have to turn your rotary encoder two steps for every trigger, set this to half step. 0 = Full step, 1 = Half step
heatEst	Heating overshoot estimator	This is a self learning estimator for the overshoot when turning the heater off. It is adjusted automatically, but you can set adjust it manually here. This does not stop further automatic adjustment.
coolEst	Cooling overshoot estimator	This is a self learning estimator for the overshoot when turning the cooler off. It is adjusted automatically, but you can set adjust it manually here. This does not stop further automatic adjustment.
minCoolTime	Minimum cooling time	*1
minCoolIdleTime	Minimum idle time before cooling	*1
minHeatTime	Minimum heating time	*1
minHeatIdleTime	Minimum idle time before heating	*1
deadTime	Minimum idle time between switch of heating and cooling.	*1

*1: Available if SettableMinimumCoolTime option is set to true, or EnableGlycol is set to true. After v2.4, it is enabled by default.

To view current temperature control setting, issue a single character

c

and send.

Sensor Calibration

The command to set sensor calibration is

U{i:0,j:0.36}

where 0 is the Device Slot that is assigned to the sensor during device setup, and 0.36 is the adjustment to the sensor.

A note about PID control

The fridge temperature is controlled with PID. The fridge setting = beer setting + PID. The proportional part is linear with the temperature error. The integral part slowly increases when an error stays present, this prevents steady state errors. The derivative part is in the opposite direction to the proportional part. This prevents overshoot: it lowers the PID value when there's 'momentum' in the right direction.