Jonas Skalman
Reading SenseAir LP8 CO2 sensor over bluetooth low energy
Dependencies: BLE_API mbed nRF51822
Diff: LP8.h
- Revision:
- 3:933dd59ad44d
- Parent:
- 2:d02255d8c36f
- Child:
- 4:320febe026ed
diff -r d02255d8c36f -r 933dd59ad44d LP8.h
--- a/LP8.h Mon Aug 14 20:52:48 2017 +0000
+++ b/LP8.h Fri Aug 18 18:20:41 2017 +0000
@@ -15,7 +15,8 @@
RES(res),
lp8Wait(_timer)
{
- Device.baud(9600); //set baud rate to 9600
+ Device.baud(9600); //set baud rate to 9600 Hz
+ Device.format(8, SerialBase::None, 2); //set bits, parity and stop bits
//initialize arrays with lp8 modbus commands.
//initial startup command:
@@ -44,15 +45,20 @@
stateRead[3] = 0x80; //starting adress
stateRead[4] = 0x2c; //number of bytes to read
stateRead[5] = 0x00; //crc_l
- stateRead[5] = 0x00; //crc_h
+ stateRead[6] = 0x00; //crc_h
+
+ //communication confirmation sequence (response from lp8)
+ confirmation[0] = 0xfe;
+ confirmation[1] = 0x41;
+ confirmation[2] = 0x81;
+ confirmation[3] = 0xe0;
//response buffer
for(int k = 0; k < 60; k++) { response[k] = 0x00; }
//variable initialization
- co2 = 400; //co2 value
- counter = 0; //
- CRC = 0x0000; //crc value
+ co2 = 400; //
+ CRC = 0x0000; //
};
@@ -60,66 +66,109 @@
//LP8 Initialization and first message
bool lp8Init(){
-// //Reset LP8
-// RES.write( 0 ); //reset
-// timeIt( 1.2 );
-// RES.write( 1 ); //enable
+ Device.format(8, SerialBase::None, 2);
+ //Reset LP8
+ RES.write( 0 ); //reset
+ timeIt( 1.0 );
+ RES.write( 1 ); //enable
+ timeIt(0.2);
//Enable Sensor
VBB_EN.write( 1 ); //power on
+
//wait for rdy signal
- timeIt( 0.35 ); //wait for lp8 rdy signal
+ timeIt( 0.30 ); //wait for lp8 rdy signal
+// while(RDY.read() != 0 ) { /* wait for rdy to go low */}
+
+ //transmit first packet
transmitPacket(firstWrite, 8); //Send out msg (and nr of bytes) over serial line
Response( 4 ); //read 4 bytes response
+
+ //check response
+ if ( responseCompare() != true){
+ //VBB_EN.write( 0 );
+ return false;
+ }
+
//compute crc
CRC = modbusCrc(stateRead, 5);
+
//add crc value to the transmit package
stateRead[5] = (uint8_t)CRC; //crc_l
stateRead[6] = (uint8_t)(CRC >> 8); //crc_h
+
//wait for rdy
- timeIt( 0.35 ); //
+ timeIt( 0.20 ); //
+// while(RDY.read() != 1 ) { /*wait for rdy to go high */}
+
transmitPacket(stateRead, 7); //transmit packet
- Response( 49 ); //read sensor state and co2 value(s)
+ Response( 49 ); //get sensor state and co2 value(s)
VBB_EN.write( 0 ); //power off lp8
- //was the talk a success? (simple check...)
- if ( getValue() < 1 ) {
- return 1; }
- else {
- return 0; }
+ return true;
};
//send subsequent messages to the lp8
- void lp8Talk(uint8_t ccByte){
+ bool lp8Talk(uint8_t inc_ccByte){
+ static const uint8_t A[] = {0xFE,0x41,0x00,0x80,0x20,0x00,0x00,0x02,0x04,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
+ 0x00,0x7F,0xFF,0x00,0x00,0x95,0xED,0x00,0x03,0x29,0x00,0x27,0x8C, 0xf5, 0x63};
+
+ Device.format(8, SerialBase::None, 2);
//transfer previous sensor state to the new msg out
for (int u = 4; u < 23+4; u++) {
stateWrite[u+2] = response[u];
}
- //Set Calibration Control Byte (see end of page for explantion)
- stateWrite[5] = ccByte;
+ //Set Calibration Control Byte (see end of page for explantion),
+ /* remove this statement if you want to be able to send anything to lp8 calculation control */
+ if( inc_ccByte != 0x20 ){ /* 0x52 is "simple recalibration, needs only one sample */
+ stateWrite[5] = inc_ccByte;
+ }
+ else {
+ stateWrite[5] = 0x20;
+ }
+
+
//compute new crc value
- CRC = modbusCrc(stateWrite, 29);
+ CRC = modbusCrc((uint8_t*)stateWrite, 29);
+
//add new crc value to send list
stateWrite[29] = (uint8_t)CRC;
stateWrite[30] = (uint8_t)(CRC >> 8);
//initialize new transfer sequence
VBB_EN.write( 1 ); //power on sensor
+
timeIt( 0.35 );
- transmitPacket(stateWrite, 31); //Send out msg with previous state (and nr of elements) over serial line
- Response( 4 ); //read 4 bytes response
+// while(RDY.read() != 0 ) { /* wait for rdy */}
+
+ transmitPacket(/*(uint8_t*)A*/(uint8_t*)stateWrite, 31); //Send out msg with previous state (and nr of elements) over serial line
+ Response( 4 ); //read 4 bytes response
+
+ //compare to confirmation sequence
+ if ( responseCompare() != true){
+ //VBB_EN.write( 0 );
+ return false;
+ }
+
//compute crc
CRC = modbusCrc(stateRead, 5);
+
//add crc value to the read request transmit package
stateRead[5] = (uint8_t)CRC; //crc_l
stateRead[6] = (uint8_t)(CRC >> 8); //crc_h
- timeIt( 0.35 );
+
+ timeIt( 0.20 );
+// while(RDY.read() != 1 ) { /* wait for rdy to go high */}
+
//send read request
transmitPacket(stateRead, 7); //transmit packet
+
//read sensor response
- Response( 49 ); //read sensor state and co2 value(s)
- VBB_EN.write( 0 ); //power off
+ Response( 49 ); //get sensor state
+ VBB_EN.write( 0 ); //power off
+
+ return true;
};
//get value from lp8 response
@@ -132,21 +181,22 @@
return val;
}
- double getTempValue()
+ float getTempValue()
{
int h = response[33];
int l = response[34];
unsigned long _temp = h * 256 + l;
- double _tempVal = 0.01 * _temp;
+ float _tempVal = 0.01 * _temp;
return _tempVal;
}
+ /* get Vcap value for at current measurement, [35],[36] is previous Vcap value */
int getVcapValue(){
- int hB = response[35];
- int lB = response[36];
+ int hB = response[37];
+ int lB = response[38];
unsigned long temp = hB * 256 + lB;
return temp;
@@ -165,8 +215,8 @@
//get calculation Control byte from lp8 response
uint8_t getCCbyte(){
- uint8_t responseCCbyte = response[0];
- return responseCCbyte;
+ uint8_t rCCbyte = stateWrite[5];
+ return rCCbyte;
}
@@ -177,21 +227,20 @@
for (int j = 0; j < bytesToPurge; j++) {
response[j] = 0x00;
}
+ //for(int k = 6; k < 31; k++) { stateWrite[k] = 0x00; } //purge sensor state
};
-//read response from lp8 (not energy efficient...)
- void Response(int bytesToRead ){
- lp8Wait.start(); //poll rx line for 0.5 seconds
+//read response from lp8
+ void Response( int bytesToRead ){
+ int Count = 0;
do {
if(Device.readable()) {
- response[counter] = Device.getc();
- counter++;
+ response[Count] = Device.getc();
+ Count++;
+ --bytesToRead;
}
}
- while( lp8Wait.read() < 0.2 );
- counter = 0;
- lp8Wait.stop();
- lp8Wait.reset();
+ while( bytesToRead > 0);
};
//transmit data over serial lines
@@ -233,6 +282,23 @@
return crc;
};
+ bool responseCompare(){
+
+ short seq = 0;
+
+ for(int j=0; j < 4; j++){
+ if(response[j] == confirmation[j]){
+ seq++;
+ }
+ }
+ //return false if check sequence fails
+ if( seq != 4 ){
+ return false;
+ }
+
+ return true;
+ }
+
//variables and buffers
private:
//pins
@@ -244,15 +310,17 @@
Timer &lp8Wait;
//msg containers
+
uint8_t firstWrite[8];
- uint8_t stateWrite[31];
+ volatile uint8_t stateWrite[31];
uint8_t stateRead[7];
- uint8_t response[60];
-
+ uint8_t confirmation[4];
+
+ volatile uint8_t response[60];
+
//
int co2; //CO2 initial value
int tempValue;
- int counter; //simple counter
uint16_t CRC; //modbus crc value