MCP23S17_Basic_IO_Demo - A simple IO demo using the MCP23S17 library

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jim hamblen / Mbed 2 deprecated MCP23S17_Basic_IO_Demo

A simple IO demo using the MCP23S17 library

Demo for Microchip MCP23S17 16-bit SPI I/O expander chip on mbed LPC1768 using hardware SPI functions. See comments in main.cpp for pin usage. This chip is still available in a DIP package, so it is easy to try on a breadboard. A complete datasheet for the Microchip MCP23SA17 SPI I/O port expander chip can be found at http://ww1.microchip.com/downloads/en/DeviceDoc/20001952c.pdf

Import program MCP23S17_Basic_IO_Demo

A simple IO demo using the MCP23S17 library

main.cpp@2:934a0500abde, 2011-01-28 (annotated)

Committer:: 4180_1
Date:: Fri Jan 28 02:04:05 2011 +0000
Revision:: 2:934a0500abde
Parent:: 1:70e1ebe47253

Who changed what in which revision?

User	Revision	Line number	New contents of line
4180_1	2:934a0500abde	1	// A simple IO demo using the MCP23S17 library
4180_1	2:934a0500abde	2	//
4180_1	2:934a0500abde	3	// MCP23S17 Library Copyright (c) 2010 Romilly Cocking
4180_1	2:934a0500abde	4	// Released under the MIT License: http://mbed.org/license/mit
4180_1	2:934a0500abde	5	//
4180_1	2:934a0500abde	6	// See http://mbed.org/users/romilly/notebook/mcp23s17-addressable-16-bit-io-expander-with-spi/
4180_1	2:934a0500abde	7	//
4180_1	2:934a0500abde	8	//
4180_1	2:934a0500abde	9	// MCP23S17 datasheet http://ww1.microchip.com/downloads/en/DeviceDoc/21952b.pdf
4180_1	2:934a0500abde	10	// uses MCP23S17 library version 0.4
4180_1	0:12f4911d7ba0	11
4180_1	0:12f4911d7ba0	12	#include "mbed.h"
4180_1	0:12f4911d7ba0	13	#include "MCP23S17.h"
4180_1	2:934a0500abde	14	// Create SPI bus
4180_1	0:12f4911d7ba0	15	SPI spi(p5, p6, p7);
4180_1	2:934a0500abde	16	//
4180_1	2:934a0500abde	17	// Wiring Connections:
4180_1	0:12f4911d7ba0	18	// mbed p5,p6,p7 are tied to MCP23S17 SI, SO, SCK pins
4180_1	2:934a0500abde	19	// mbed p20 to MCP23S17 CS
4180_1	2:934a0500abde	20	// MCP23S17 reset pin pulled high
4180_1	2:934a0500abde	21	// MCP23S17 GPA0 connected to GPB0 for loopback test
4180_1	0:12f4911d7ba0	22	// A0, A1, A2 of the MCP23S17 are tied to ground on the breadboard, so the 8-bit address for writes is 0x40
4180_1	0:12f4911d7ba0	23	// This is referred to as the opcode in the device datasheet
4180_1	2:934a0500abde	24	char Opcode = 0x40;
4180_1	0:12f4911d7ba0	25
4180_1	0:12f4911d7ba0	26	// Next create a MCP23S17
4180_1	0:12f4911d7ba0	27	// mbed p20 is connected to ~chipSelect on the MCP23S17
4180_1	2:934a0500abde	28	MCP23S17 chip = MCP23S17(spi, p20, Opcode);
4180_1	0:12f4911d7ba0	29
4180_1	2:934a0500abde	30	// Optional software reset - mbed p14 to MCP23S17 reset pin
4180_1	2:934a0500abde	31	// DigitalOut reset(p14);
4180_1	1:70e1ebe47253	32
4180_1	0:12f4911d7ba0	33	DigitalOut led1(LED1); // mbed LED1 is used for test status display
4180_1	0:12f4911d7ba0	34
4180_1	0:12f4911d7ba0	35	int main() {
4180_1	1:70e1ebe47253	36	// The MCP23S17 reset pin can just be pulled high, since it has a power on reset circuit.
4180_1	1:70e1ebe47253	37	// The reset pin can be used for a software forced reset by pulling it low with an mbed GPIO pin.
4180_1	1:70e1ebe47253	38	// But just leave it pulled high for this simple demo code.
4180_1	0:12f4911d7ba0	39	// After a power on reset, both IO ports default to input mode
4180_1	0:12f4911d7ba0	40	//
4180_1	1:70e1ebe47253	41	// Here is the optional code for a software reset
4180_1	1:70e1ebe47253	42	// reset = 0;
4180_1	1:70e1ebe47253	43	// wait_us(1);
4180_1	1:70e1ebe47253	44	// reset = 1;
4180_1	1:70e1ebe47253	45	//
4180_1	0:12f4911d7ba0	46	// Set all 8 Port A bits to output direction
4180_1	0:12f4911d7ba0	47	chip.direction(PORT_A, 0x00);
4180_1	0:12f4911d7ba0	48	// Set all 8 Port B bits to input direction
4180_1	0:12f4911d7ba0	49	chip.direction(PORT_B, 0xFF);
4180_1	0:12f4911d7ba0	50	led1=0;
4180_1	0:12f4911d7ba0	51	// Start Loopback test sending out and reading back values
4180_1	0:12f4911d7ba0	52	// loopback test uses A0 and B0 pins - so use a wire to jumper those two pins on MCP23S17 together
4180_1	0:12f4911d7ba0	53	while (1) {
4180_1	0:12f4911d7ba0	54	// write 0xAA to MCP23S17 Port A
4180_1	0:12f4911d7ba0	55	chip.write(PORT_A, 0xAA);
4180_1	0:12f4911d7ba0	56	wait(.5);
4180_1	0:12f4911d7ba0	57	// read back value from MCP23S17 Port B and display B0 on mbed led1
4180_1	0:12f4911d7ba0	58	led1 = chip.read(PORT_B)& 0x01;
4180_1	0:12f4911d7ba0	59	// write 0x55 to MCP23S17 Port A
4180_1	0:12f4911d7ba0	60	chip.write(PORT_A, 0x55);
4180_1	0:12f4911d7ba0	61	wait(.5);
4180_1	0:12f4911d7ba0	62	// read back value from MCP23S17 Port B and display B0 on mbed led1
4180_1	0:12f4911d7ba0	63	led1 = chip.read(PORT_B)& 0x01;
4180_1	2:934a0500abde	64	// led1 should blink slowly when it is all working
4180_1	0:12f4911d7ba0	65	}
4180_1	0:12f4911d7ba0	66	}