Zhen Liu
/
HW1_extraE
Extra problem 5 for HW 1
Fork of MCP23S17_Basic_IO_Demo by
main.cpp
- Committer:
- lzzcd001
- Date:
- 2015-02-18
- Revision:
- 3:07745b21792d
- Parent:
- 2:934a0500abde
File content as of revision 3:07745b21792d:
// A simple IO demo using the MCP23S17 library // // MCP23S17 Library Copyright (c) 2010 Romilly Cocking // Released under the MIT License: http://mbed.org/license/mit // // See http://mbed.org/users/romilly/notebook/mcp23s17-addressable-16-bit-io-expander-with-spi/ // // // MCP23S17 datasheet http://ww1.microchip.com/downloads/en/DeviceDoc/21952b.pdf // uses MCP23S17 library version 0.4 #include "mbed.h" #include "MCP23S17.h" // Create SPI bus SPI spi(p5, p6, p7); DigitalOut a(p21); // // Wiring Connections: // mbed p5,p6,p7 are tied to MCP23S17 SI, SO, SCK pins // mbed p20 to MCP23S17 CS // MCP23S17 reset pin pulled high // MCP23S17 GPA0 connected to GPB0 for loopback test // A0, A1, A2 of the MCP23S17 are tied to ground on the breadboard, so the 8-bit address for writes is 0x40 // This is referred to as the opcode in the device datasheet char Opcode = 0x40; char OpcodeIn = 0x42; // Next create a MCP23S17 // mbed p20 is connected to ~chipSelect on the MCP23S17 MCP23S17 chip = MCP23S17(spi, p20, Opcode); MCP23S17 chip2 = MCP23S17(spi, p20, OpcodeIn); // Optional software reset - mbed p14 to MCP23S17 reset pin // DigitalOut reset(p14); DigitalOut led1(LED1); // mbed LED1 is used for test status display int main() { a = 1; // The MCP23S17 reset pin can just be pulled high, since it has a power on reset circuit. // The reset pin can be used for a software forced reset by pulling it low with an mbed GPIO pin. // But just leave it pulled high for this simple demo code. // After a power on reset, both IO ports default to input mode // // Here is the optional code for a software reset // reset = 0; // wait_us(1); // reset = 1; // // Set all 8 Port A bits to output direction chip.direction(PORT_A, 0x00); // Set all 8 Port B bits to input direction chip.direction(PORT_B, 0xFF); chip2.direction(PORT_A, 0x00); chip2.direction(PORT_B, 0xFF); led1=0; int mid = 0; // Start Loopback test sending out and reading back values // loopback test uses A0 and B0 pins - so use a wire to jumper those two pins on MCP23S17 together while (1) { // write 0xAA to MCP23S17 Port A mid = chip.read(PORT_B) & 0x01; wait(.1); chip.write(PORT_A, mid); // read back value from MCP23S17 Port B and display B0 on mbed led1 wait(.1); mid = chip2.read(PORT_B); wait(.1); // write 0x55 to MCP23S17 Port A chip2.write(PORT_A, mid); wait(.1); // led1 should blink slowly when it is all working } }