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So far I've used this protocol for a smart fridge and a bilirubin measurement device (for testing Jaundice). Because popular Arduino Bluetooth interfaces happen to act as media independent serial lines, this will also work with Bluetooth. http://www.electronica60norte.com/mwfls/pdf/newBluetooth.pdf Responses are returned in the 'value' or 'error' parameters during reads. The 'value' parameter is used as the source during writes. import serial import struct import time params = ('option', 'pin', 'value', 'error') ser = serial.Serial('COM3') # opening a serial connection to arduino over USB will reset the device ser.read(1) # wait for ready signal so we know that arduino came back online. ser.write(struct.pack('<hhhh', 0, 0, 0, 0)) response = struct.unpack('<hhhh', ser.read(8)) print(dict(zip(params, response)) /* * ComPacket Data Structure * >option: 0 = Analog Read, 1 = Digital Read, 2 = Analog Write, 3 = Digital Write * >pin: pin to read/write from * >value: Arduino will return pin value to this variable. Leave empty on request * >error: Arduino will return an Error code is there's a problem with the request, or reading a pin value */ enum ComPacket_option {A_READ, D_READ, A_WRITE, D_WRITE}; enum ComPacket_error {INVALID_OPTION, INVALID_READ_PIN, INVALID_WRITE_PIN}; struct ComPacket { enum ComPacket_option option; int pin; int value; enum ComPacket_error error; } buf; void ComPacket_zero(ComPacket *packet) { packet->option = (enum ComPacket_option) 0; packet->pin = 0; packet->value = 0; packet->error = (enum ComPacket_error) 0; } void ComPacket_handleRead(ComPacket *packet) { if (packet->option == A_READ) { packet->value = analogRead(packet->pin); return; } if (packet->option == D_READ) { packet->value = digitalRead(packet->pin); return; } } void ComPacket_handleWrite(ComPacket *packet) { if (packet->option == A_WRITE) { analogWrite(packet->pin, packet->value); return; } if (packet->option == D_WRITE) { digitalWrite(packet->pin, packet->value); return; } } void ComPacket_handleError(ComPacket *packet, enum ComPacket_error error) { ComPacket_zero(packet); packet->error = error; } void ComPacket_processPacket(ComPacket *packet) { switch (packet->option) { case A_READ: case D_READ: ComPacket_handleRead(packet); break; case A_WRITE: case D_WRITE: ComPacket_handleWrite(packet); break; default: ComPacket_handleError(packet, INVALID_OPTION); } } /* * ******************* END COMPACKET */ // Use Serial1 for TX/RX pins /* * https://www.arduino.cc/reference/tr/language/functions/communication/serial/ * Serial, Serial1, Serial2 and Serial3 are available. See reference for which you need */ auto SerialDevice = Serial; void setup() { // put your setup code here, to run once: ComPacket_zero(&buf); SerialDevice.begin(9600,SERIAL_8N1); // wait for serial port to connect. Needed for native USB while (!SerialDevice); SerialDevice.write(1); } void loop() { // check if data available if (SerialDevice.available() > 0) { // if so process packet and send back result SerialDevice.readBytes((char*)&buf, sizeof(ComPacket)); ComPacket_processPacket(&buf); SerialDevice.write((char*)&buf, sizeof(ComPacket)); SerialDevice.flush(); } }