Diff: main.cpp

Revision:

0:b08b1d99aaf3

diff -r 000000000000 -r b08b1d99aaf3 main.cpp
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+++ b/main.cpp	Thu Jan 18 18:15:18 2018 +0000
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+// 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);
+// 
+// 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;
+
+// Next create a MCP23S17
+// mbed p20 is connected to ~chipSelect on the MCP23S17
+MCP23S17 chip = MCP23S17(spi, p20, Opcode);
+
+// Optional software reset - mbed p14 to MCP23S17 reset pin
+   DigitalOut reset(p14);
+
+
+int main() {
+//  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);
+
+//  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) {
+
+        // read back value from MCP23S17 Port B and display B0 on mbed led1
+        int led = !(chip.read(PORT_B) & 0x01);
+        chip.write(PORT_A, led);
+        // led1 should blink slowly when it is all working
+    }
+}