Apply IIR Low-pass Filter to MQTT value
Take incoming value from MQTT topic get/ESP8266/counterValue and apply and IIR (Infinate Impulse Response) Low-pass filter to it and output to topic get/ESP8266/filterValue. The filter constant can be set via topic set/ESP8266/filterConstant. Most functionality resides in the main filter function.
[{"id":"80804206.7f7fc","type":"mqtt-broker","broker":"localhost","port":"1883","clientid":""},{"id":"22f2ce73.dd0d32","type":"mqtt in","name":"","topic":"get/ESP8266/counterValue","broker":"80804206.7f7fc","x":146,"y":90,"z":"1e47102.fe1b8f","wires":[["4b72bd0e.b48d44"]]},{"id":"4b72bd0e.b48d44","type":"function","name":"Filter","func":"switch (msg.topic) {\n case \"get/ESP8266/counterValue\":\n context.filterValue = context.filterValue || 0;\n var filterConstant = context.filterConstant || 0.4;\n var unfiltered = msg.payload;\n var filtered = ((unfiltered - context.filterValue) * filterConstant) + context.filterValue;\n context.filterValue = Math.round(filtered);\n msg.topic = \"get/ESP8266/filterValue\";\n msg.payload = context.filterValue;\n return msg;\n break;\n case \"set/ESP8266/filterConstant\":\n if (msg.payload >= 0.0 && msg.payload <= 1.0) {\n context.filterConstant = msg.payload;\n msg.topic = \"get/ESP8266/filterConstant\";\n msg.payload = context.filterConstant;\n msg.retain = true;\n return msg;\n }\n break;\n}\n\nreturn null;","outputs":1,"x":456,"y":204,"z":"1e47102.fe1b8f","wires":[["a099df33.5f662","ec7fa690.138058"]]},{"id":"a099df33.5f662","type":"mqtt out","name":"MQTT out","topic":"","broker":"80804206.7f7fc","x":796,"y":262,"z":"1e47102.fe1b8f","wires":[]},{"id":"ec7fa690.138058","type":"debug","name":"","active":false,"console":false,"complete":false,"x":795,"y":123,"z":"1e47102.fe1b8f","wires":[]},{"id":"84c0cef8.7b3f3","type":"mqtt in","name":"","topic":"set/ESP8266/filterConstant","broker":"80804206.7f7fc","x":151,"y":248,"z":"1e47102.fe1b8f","wires":[["4b72bd0e.b48d44"]]}]
