MCP3021
MCP3021.cpp
- Committer:
- Reiko
- Date:
- 2014-09-02
- Revision:
- 0:423652b49d07
File content as of revision 0:423652b49d07:
#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; }