MCP3021
Diff: MCP3021.cpp
- Revision:
- 0:423652b49d07
--- /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