Bluetooth Packet Encoding
This is the c code used to construct the packets on the Arduino:
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/** ================================== */
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/** BLUETOOTH DATA PACKETING FUNCTIONS */
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/** ================================== */
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/** The two functions in this section handle packeting the data and sending it over USART to the bluetooth module. The two functions are
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* identically named so are called the in the same way, however the first is run if the value passed to it is a float and the second is
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* run if the value passed into it is an integer (an override function). For all intents and purposes you can ignore this and simply call
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* 'sendData(identifier, value);' using one of the defined identifiers and either a float or integer value to send informaion over BT.
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*
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* identifier: see definitions at start of code
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* value: the value to send (typically some caluclated value from a sensor)
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*/
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​
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void sendData(char identifier, float value)
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{
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if (!DEBUG_MODE) // Only runs if debug mode is LOW (0)
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{
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byte dataByte1;
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byte dataByte2;
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​
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if (value == 0)
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{
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// It is impossible to send null bytes over Serial connection
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// so instead we define zero as 0xFF or 11111111 i.e. 255
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dataByte1 = 0xFF;
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dataByte2 = 0xFF;
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​
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}
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else if (value <= 127)
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{
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// Values under 128 are sent as a float
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// i.e. value = dataByte1 + dataByte2 / 100
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int integer;
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int decimal;
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float tempDecimal;
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​
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integer = (int) value;
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tempDecimal = (value - (float) integer) * 100;
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decimal = (int) tempDecimal;
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​
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dataByte1 = (byte) integer;
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dataByte2 = (byte) decimal;
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​
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if (decimal == 0)
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{
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dataByte2 = 0xFF;
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}
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​
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if (integer == 0)
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{
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dataByte1 = 0xFF;
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}
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​
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}
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else
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{
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// Values above 127 are sent as integer
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// i.e. value = dataByte1 * 100 + dataByte2
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int tens;
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int hundreds;
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​
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hundreds = (int)(value / 100);
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tens = value - hundreds * 100;
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​
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dataByte1 = (byte)hundreds;
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//dataByte1 = dataByte1 || 0x10000000; //flag for integer send value
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dataByte1 += 128;
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dataByte2 = (byte) tens;
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​
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if (tens == 0)
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{
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dataByte2 = 0xFF;
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}
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​
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if (hundreds == 0)
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{
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dataByte1 = 0xFF;
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}
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}
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​
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// Send the data in the format { [id] [1] [2] }
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Serial.write(123);
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Serial.write(identifier);
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Serial.write(dataByte1);
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Serial.write(dataByte2);
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Serial.write(125);
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​
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}
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​
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}
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​
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/** override for integer values*/
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void sendData(char identifier, int value)
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{
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if (!DEBUG_MODE)
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{
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byte dataByte1;
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byte dataByte2;
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​
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if (value == 0)
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{
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dataByte1 = 0xFF;
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dataByte2 = 0xFF;
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​
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}
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else if (value <= 127)
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{
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​
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dataByte1 = (byte)value;
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dataByte2 = 0xFF; //we know there's no decimal component as an int was passed in
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}
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else
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{
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int tens;
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int hundreds;
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​
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hundreds = (int)(value / 100);
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tens = value - hundreds * 100;
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​
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dataByte1 = (byte)hundreds;
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dataByte1 += 128; //sets MSB High to indicate Integer value
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dataByte2 = (byte) tens;
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​
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if (tens == 0)
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{
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dataByte2 = 0xFF;
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}
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​
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if (hundreds == 0)
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{
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dataByte1 = 0xFF;
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}
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}
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​
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Serial.write(123);
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Serial.write(identifier);
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Serial.write(dataByte1);
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Serial.write(dataByte2);
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Serial.write(125);
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}
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​
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}
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If you adapt it to any other languages we would be keen to show the code here!
Last modified 4yr ago
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