Diff: MCP3021.cpp

Revision:

0:423652b49d07

diff -r 000000000000 -r 423652b49d07 MCP3021.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MCP3021.cpp	Tue Sep 02 15:34:15 2014 +0000
@@ -0,0 +1,45 @@
+#include "MCP3021.h"
+ 
+//Create instance
+MCP3021::MCP3021(PinName sda, PinName scl, float supplyVoltage) : i2c(sda, scl), _supplyVoltage(supplyVoltage) {
+}
+ 
+//destroy instance
+MCP3021::~MCP3021() {
+}
+ 
+float MCP3021::read() {
+ 
+//You cannot write to an MCP3021, it has no writable registers.
+//MCP3021 also requires an ACKnowledge between each byte sent, before it will send the next byte. So we need to be a bit manual with how we talk to it.
+//It also needs an (NOT) ACKnowledge after the second byte or it will keep sending bytes (continuous sampling)
+//
+//From the datasheet.
+//
+//I2C.START
+//Send 8 bit device/ part address to open conversation.   (See .h file for part explanation)
+//read a byte (with ACK)
+//read a byte (with NAK)
+//I2C.STOP
+ 
+ 
+  //  char data[2];
+ 
+    i2c.start();
+    int acknowledged = i2c.write(MCP3021_CONVERSE); //send a byte to start the conversation. It should be acknowledged.
+    _data[0] = i2c.read(1);  //read a byte. acknowledge when we have it.
+    _data[1] = i2c.read(0);  //read the second byte. (n)acknowledge when we have it to stop the flow.
+    i2c.stop();
+ 
+    //convert to 12 bit.
+    short res;
+    int _10_bit_var; // 2 bytes
+    char _4_bit_MSnibble = _data[0]; // 1 byte, example 0000 1000
+    char _6_bit_LSByte = _data[1];   // 1 byte, example 1111 0000
+ 
+    _10_bit_var = ((0x0F & _4_bit_MSnibble) << 6) | _6_bit_LSByte >> 2;   //example 100011110000
+    res = _10_bit_var;
+ 
+    return  (_supplyVoltage / 1024) * res;
+ 
+}
\ No newline at end of file