Wim Huiskamp / PCF8574_Bus

PCF8574 I2C Portexpanders used to provide data, address and controlbus interface

Dependents:   mbed_bus

PCF8574_DataBus.cpp@0:12207c70f4ea, 2015-01-25 (annotated)

Committer:
wim
Date:
Sun Jan 25 17:50:03 2015 +0000
Revision:
0:12207c70f4ea
PCF8574 Bus Class. First release, converted into lib.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
wim 0:12207c70f4ea 1 /* PCF8574_DataBus - Use the PCF8574 I2C Port Extender for controlling the Data Bus
wim 0:12207c70f4ea 2 * Copyright (c) 2011 Wim Huiskamp
wim 0:12207c70f4ea 3 *
wim 0:12207c70f4ea 4 * Released under the MIT License: http://mbed.org/license/mit
wim 0:12207c70f4ea 5 *
wim 0:12207c70f4ea 6 * version 0.2 Initial Release
wim 0:12207c70f4ea 7 */
wim 0:12207c70f4ea 8 #include "mbed.h"
wim 0:12207c70f4ea 9 #include "PCF8574_DataBus.h"
wim 0:12207c70f4ea 10
wim 0:12207c70f4ea 11 /** Create an PCF8574_DataBus object connected to the specified I2C object and using the specified deviceAddress
wim 0:12207c70f4ea 12 *
wim 0:12207c70f4ea 13 * @param I2C &i2c the I2C port to connect to
wim 0:12207c70f4ea 14 * @param char deviceAddress the address of the PCF8574
wim 0:12207c70f4ea 15 */
wim 0:12207c70f4ea 16 PCF8574_DataBus::PCF8574_DataBus(I2C &i2c, char deviceAddress) : _i2c(i2c) {
wim 0:12207c70f4ea 17 _writeOpcode = deviceAddress & 0xFE; // low order bit = 0 for write
wim 0:12207c70f4ea 18 _readOpcode = deviceAddress | 0x01; // low order bit = 1 for read
wim 0:12207c70f4ea 19 _init();
wim 0:12207c70f4ea 20 }
wim 0:12207c70f4ea 21
wim 0:12207c70f4ea 22 /** Optimised DataBus write operation.
wim 0:12207c70f4ea 23 * @param byte the datavalue to output on the bus
wim 0:12207c70f4ea 24 */
wim 0:12207c70f4ea 25 void PCF8574_DataBus::write(char byte) {
wim 0:12207c70f4ea 26 char data[1];
wim 0:12207c70f4ea 27
wim 0:12207c70f4ea 28 data[0] = byte;
wim 0:12207c70f4ea 29 _i2c.write(_writeOpcode, data, 1); // Write datavalue to bus
wim 0:12207c70f4ea 30 }
wim 0:12207c70f4ea 31
wim 0:12207c70f4ea 32 /** Optimised DataBus read operation.
wim 0:12207c70f4ea 33 *
wim 0:12207c70f4ea 34 * @returns current data from Databus
wim 0:12207c70f4ea 35 */
wim 0:12207c70f4ea 36 char PCF8574_DataBus::read() {
wim 0:12207c70f4ea 37 char data[1];
wim 0:12207c70f4ea 38
wim 0:12207c70f4ea 39 //Make sure that databus is enabled for Read
wim 0:12207c70f4ea 40 // data[0] = 0xFF; // Init Port for datainput by Writing 0xFF
wim 0:12207c70f4ea 41 // _i2c.write(_writeOpcode, data, 1); // Write to bus
wim 0:12207c70f4ea 42
wim 0:12207c70f4ea 43 _i2c.read(_readOpcode, data, 1); // Read data from bus
wim 0:12207c70f4ea 44
wim 0:12207c70f4ea 45 return data[0];
wim 0:12207c70f4ea 46 }
wim 0:12207c70f4ea 47
wim 0:12207c70f4ea 48
wim 0:12207c70f4ea 49 /** Enable databus for Write or Read
wim 0:12207c70f4ea 50 *
wim 0:12207c70f4ea 51 * @param Bus_Dir bus_dir
wim 0:12207c70f4ea 52 */
wim 0:12207c70f4ea 53 void PCF8574_DataBus::busdir (Bus_Dir bus_dir) {
wim 0:12207c70f4ea 54
wim 0:12207c70f4ea 55 if (bus_dir == READ) {
wim 0:12207c70f4ea 56 // Make sure that databus is enabled for READ
wim 0:12207c70f4ea 57 write(0xFF); // Init Port as input by Writing 0xFF
wim 0:12207c70f4ea 58
wim 0:12207c70f4ea 59 }
wim 0:12207c70f4ea 60 else {
wim 0:12207c70f4ea 61 // Make sure that databus is enabled for WRITE
wim 0:12207c70f4ea 62 write(0xFF); // Not really needed, just Init Port to safe settings
wim 0:12207c70f4ea 63 }
wim 0:12207c70f4ea 64 }
wim 0:12207c70f4ea 65
wim 0:12207c70f4ea 66
wim 0:12207c70f4ea 67
wim 0:12207c70f4ea 68 /** Init PCF8574_DataBus
wim 0:12207c70f4ea 69 * @param
wim 0:12207c70f4ea 70 * @returns
wim 0:12207c70f4ea 71 */
wim 0:12207c70f4ea 72 void PCF8574_DataBus::_init() {
wim 0:12207c70f4ea 73
wim 0:12207c70f4ea 74 busdir(WRITE); // Init Port as output
wim 0:12207c70f4ea 75 }