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 // 
00017 // Wiring Connections:
00018 // mbed p5,p6,p7 are tied to MCP23S17 SI, SO, SCK pins
00019 // mbed p20 to MCP23S17 CS
00020 // MCP23S17 reset pin pulled high
00021 // MCP23S17 GPA0 connected to GPB0 for loopback test
00022 // A0, A1, A2 of the MCP23S17  are tied to ground on the breadboard, so the 8-bit address for writes is 0x40
00023 // This is referred to as the opcode in the device datasheet
00024 char Opcode = 0x40;
00025 
00026 // Next create a MCP23S17
00027 // mbed p20 is connected to ~chipSelect on the MCP23S17
00028 MCP23S17 chip = MCP23S17(spi, p20, Opcode);
00029 
00030 // Optional software reset - mbed p14 to MCP23S17 reset pin
00031    DigitalOut reset(p14);
00032 
00033 
00034 int main() {
00035 //  The MCP23S17 reset pin can just be pulled high, since it has a power on reset circuit.
00036 //  The reset pin can be used for a software forced reset by pulling it low with an mbed GPIO pin.
00037 //  But just leave it pulled high for this simple demo code.
00038 //  After a power on reset, both IO ports default to input mode
00039 //
00040 //  Here is the optional code for a software reset
00041     reset = 0;
00042     wait_us(1);
00043     reset = 1;
00044 //
00045 //  Set all 8 Port A bits to output direction
00046     chip.direction(PORT_A, 0x00);
00047 //  Set all 8 Port B bits to input direction
00048     chip.direction(PORT_B, 0xFF);
00049 
00050 //  Start Loopback test sending out and reading back values
00051 //  loopback test uses A0 and B0 pins - so use a wire to jumper those two pins on MCP23S17 together
00052     while (1) {
00053 
00054         // read back value from MCP23S17 Port B and display B0 on mbed led1
00055         int led = !(chip.read(PORT_B) & 0x01);
00056         chip.write(PORT_A, led);
00057         // led1 should blink slowly when it is all working
00058     }
00059 }