Revision 0:89572af84e82, committed 2013-11-07

Comitter:

Parkz

Date:

Thu Nov 07 14:08:31 2013 +0000

Commit message:

Calculates pressure using MPL115A1. Calibrated to show 0 for room atmosphere.

Changed in this revision

diff -r 000000000000 -r 89572af84e82 mpl115a1.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mpl115a1.h	Thu Nov 07 14:08:31 2013 +0000
@@ -0,0 +1,77 @@
+#ifndef MPL115A1_H
+#define MPL115A1_H
+// MPL115A1 register address map
+#define MPL115A1_STARTPRES 0x20 // start pressure measurement
+#define MPL115A1_PRESH    0x00    // 80
+#define MPL115A1_PRESL    0x02    // 82
+#define MPL115A1_A0MSB    0x08    // 88
+#define MPL115A1_A0LSB    0x0A    // 8A
+#define MPL115A1_B1MSB    0x0C    // 8C
+#define MPL115A1_B1LSB    0x0E    // 8E
+#define MPL115A1_B2MSB    0x10    // 90
+#define MPL115A1_B2LSB    0x12    // 92
+#define MPL115A1_C12MSB   0x14    // 94
+#define MPL115A1_C12LSB   0x16    // 96
+#define MPL115A1_C11MSB   0x18    // 98
+#define MPL115A1_C11LSB   0x1A    // 9A
+#define MPL115A1_C22MSB   0x1C    // 9C
+#define MPL115A1_C22LSB   0x1E    // 9E
+SPI spi(p5,p6,p7);
+DigitalOut sdn(p8);
+DigitalOut cs(p9);
+    long int uiPadc;
+    unsigned char uiPH, uiPL;
+unsigned int readRegister(uint8_t address);
+void writeRegister(uint8_t address, char data);
+float calculatePressurekPa()
+{
+    // read pressure, temperature and coefficients, calculate and return absolute pressure [kPa]
+float p;
+    writeRegister(MPL115A1_STARTPRES, 0x00); // start temperature and pressure conversions
+    wait_ms(2); // AN: data is typically ready after 3ms, DS for both: max. 1ms
+    
+    // read raw pressure
+    uiPH = readRegister(MPL115A1_PRESH);
+    uiPL = readRegister(MPL115A1_PRESL);
+        
+    uiPadc = (unsigned int) uiPH << 8;
+    uiPadc += (unsigned int) uiPL & 0x00FF;
+    uiPadc-=28800;
+    uiPadc= -uiPadc;
+    p=uiPadc/128;
+    return p;
+    
+   
+}
+unsigned int readRegister(uint8_t address)
+{
+    // returns the contents of any 1 byte register from any address
+    // sets the MSB for every address byte (READ mode)
+
+    unsigned int byte;
+
+    address |= 0x80;
+
+    cs = 0;
+    spi.write(address);
+    byte = spi.write(0x00);
+    cs = 1;
+
+    return byte;
+}
+void writeRegister(uint8_t address, char data)
+{
+    //write any data byte to any single address
+    //adds a 0 to the MSB of the address byte (WRITE mode)
+
+    address &= 0x7F;
+
+    cs = 0;
+    wait_ms(1);
+    spi.write(address);
+    wait_ms(1);
+    spi.write(data);
+    wait_ms(1);
+    cs = 1;
+}
+#endif
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