main.cpp

00001 // A simple IO demo using the MCP23S17 library
00002 //
00003 // MCP23S17 Library Copyright (c) 2010 Romilly Cocking
00004 // Released under the MIT License: http://mbed.org/license/mit
00005 //
00006 // See http://mbed.org/users/romilly/notebook/mcp23s17-addressable-16-bit-io-expander-with-spi/
00007 //
00008 //
00009 // MCP23S17 datasheet http://ww1.microchip.com/downloads/en/DeviceDoc/21952b.pdf
00010 // uses MCP23S17 library version 0.4
00011 
00012 #include "mbed.h"
00013 #include "MCP23S17.h"
00014 // Create SPI bus
00015 SPI spi(p5, p6, p7);
00016 DigitalOut a(p21);
00017 
00018 // 
00019 // Wiring Connections:
00020 // mbed p5,p6,p7 are tied to MCP23S17 SI, SO, SCK pins
00021 // mbed p20 to MCP23S17 CS
00022 // MCP23S17 reset pin pulled high
00023 // MCP23S17 GPA0 connected to GPB0 for loopback test
00024 // A0, A1, A2 of the MCP23S17  are tied to ground on the breadboard, so the 8-bit address for writes is 0x40
00025 // This is referred to as the opcode in the device datasheet
00026 char Opcode = 0x40;
00027 char OpcodeIn = 0x42;
00028 
00029 // Next create a MCP23S17
00030 // mbed p20 is connected to ~chipSelect on the MCP23S17
00031 MCP23S17 chip = MCP23S17(spi, p20, Opcode);
00032 MCP23S17 chip2 = MCP23S17(spi, p20, OpcodeIn);
00033 
00034 // Optional software reset - mbed p14 to MCP23S17 reset pin
00035 // DigitalOut reset(p14);
00036 
00037 DigitalOut led1(LED1); // mbed LED1 is used for test status display
00038 
00039 int main() {
00040     a = 1;
00041 //  The MCP23S17 reset pin can just be pulled high, since it has a power on reset circuit.
00042 //  The reset pin can be used for a software forced reset by pulling it low with an mbed GPIO pin.
00043 //  But just leave it pulled high for this simple demo code.
00044 //  After a power on reset, both IO ports default to input mode
00045 //
00046 //  Here is the optional code for a software reset
00047 //  reset = 0;
00048 //  wait_us(1);
00049 //  reset = 1;
00050 //
00051 //  Set all 8 Port A bits to output direction
00052     chip.direction(PORT_A, 0x00);
00053 //  Set all 8 Port B bits to input direction
00054     chip.direction(PORT_B, 0xFF);
00055     chip2.direction(PORT_A, 0x00);
00056     chip2.direction(PORT_B, 0xFF);
00057     led1=0;
00058     int mid = 0;
00059 //  Start Loopback test sending out and reading back values
00060 //  loopback test uses A0 and B0 pins - so use a wire to jumper those two pins on MCP23S17 together
00061     while (1) {
00062         // write 0xAA to MCP23S17 Port A
00063         mid = chip.read(PORT_B) & 0x01;
00064         wait(.1);
00065         chip.write(PORT_A, mid);
00066         // read back value from MCP23S17 Port B and display B0 on mbed led1
00067         wait(.1);
00068         mid = chip2.read(PORT_B);
00069         wait(.1);
00070         // write 0x55 to MCP23S17 Port A
00071         chip2.write(PORT_A, mid);
00072         wait(.1);
00073         // led1 should blink slowly when it is all working
00074     }
00075 }