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4180_lab1_part7_ec
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main.cpp@1:26e3d87d1f49, 2018-01-22 (annotated)
- Committer:
- Josahty
- Date:
- Mon Jan 22 18:34:48 2018 +0000
- Revision:
- 1:26e3d87d1f49
- Parent:
- 0:8efa2ed1bc48
ec
Who changed what in which revision?
User | Revision | Line number | New contents of line |
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Josahty | 0:8efa2ed1bc48 | 1 | // A simple IO demo using the MCP23S17 library |
Josahty | 0:8efa2ed1bc48 | 2 | // |
Josahty | 0:8efa2ed1bc48 | 3 | // MCP23S17 Library Copyright (c) 2010 Romilly Cocking |
Josahty | 0:8efa2ed1bc48 | 4 | // Released under the MIT License: http://mbed.org/license/mit |
Josahty | 0:8efa2ed1bc48 | 5 | // |
Josahty | 0:8efa2ed1bc48 | 6 | // See http://mbed.org/users/romilly/notebook/mcp23s17-addressable-16-bit-io-expander-with-spi/ |
Josahty | 0:8efa2ed1bc48 | 7 | // |
Josahty | 0:8efa2ed1bc48 | 8 | // |
Josahty | 0:8efa2ed1bc48 | 9 | // MCP23S17 datasheet http://ww1.microchip.com/downloads/en/DeviceDoc/21952b.pdf |
Josahty | 0:8efa2ed1bc48 | 10 | // uses MCP23S17 library version 0.4 |
Josahty | 0:8efa2ed1bc48 | 11 | |
Josahty | 0:8efa2ed1bc48 | 12 | #include "mbed.h" |
Josahty | 0:8efa2ed1bc48 | 13 | #include "MCP23S17.h" |
Josahty | 0:8efa2ed1bc48 | 14 | // Create SPI bus |
Josahty | 0:8efa2ed1bc48 | 15 | SPI spi(p5, p6, p7); |
Josahty | 0:8efa2ed1bc48 | 16 | // |
Josahty | 0:8efa2ed1bc48 | 17 | // Wiring Connections: |
Josahty | 0:8efa2ed1bc48 | 18 | // mbed p5,p6,p7 are tied to MCP23S17 SI, SO, SCK pins |
Josahty | 0:8efa2ed1bc48 | 19 | // mbed p20 to MCP23S17 CS |
Josahty | 0:8efa2ed1bc48 | 20 | // MCP23S17 reset pin pulled high |
Josahty | 0:8efa2ed1bc48 | 21 | // MCP23S17 GPA0 connected to GPB0 for loopback test |
Josahty | 0:8efa2ed1bc48 | 22 | // A0, A1, A2 of the MCP23S17 are tied to ground on the breadboard, so the 8-bit address for writes is 0x40 |
Josahty | 0:8efa2ed1bc48 | 23 | // This is referred to as the opcode in the device datasheet |
Josahty | 1:26e3d87d1f49 | 24 | char OpcodeA = 0x40; |
Josahty | 1:26e3d87d1f49 | 25 | char OpcodeB = 0x42; |
Josahty | 0:8efa2ed1bc48 | 26 | |
Josahty | 0:8efa2ed1bc48 | 27 | // Next create a MCP23S17 |
Josahty | 0:8efa2ed1bc48 | 28 | // mbed p20 is connected to ~chipSelect on the MCP23S17 |
Josahty | 1:26e3d87d1f49 | 29 | MCP23S17 chip1 = MCP23S17(spi, p20, OpcodeA); |
Josahty | 1:26e3d87d1f49 | 30 | MCP23S17 chip2 = MCP23S17(spi, p21, OpcodeB); |
Josahty | 0:8efa2ed1bc48 | 31 | |
Josahty | 0:8efa2ed1bc48 | 32 | // Optional software reset - mbed p14 to MCP23S17 reset pin |
Josahty | 0:8efa2ed1bc48 | 33 | // DigitalOut reset(p14); |
Josahty | 0:8efa2ed1bc48 | 34 | |
Josahty | 1:26e3d87d1f49 | 35 | DigitalOut led1(p22); // mbed LED1 is used for test status display |
Josahty | 1:26e3d87d1f49 | 36 | DigitalIn pb(p19); |
Josahty | 0:8efa2ed1bc48 | 37 | |
Josahty | 0:8efa2ed1bc48 | 38 | int main() { |
Josahty | 0:8efa2ed1bc48 | 39 | // The MCP23S17 reset pin can just be pulled high, since it has a power on reset circuit. |
Josahty | 0:8efa2ed1bc48 | 40 | // The reset pin can be used for a software forced reset by pulling it low with an mbed GPIO pin. |
Josahty | 0:8efa2ed1bc48 | 41 | // But just leave it pulled high for this simple demo code. |
Josahty | 0:8efa2ed1bc48 | 42 | // After a power on reset, both IO ports default to input mode |
Josahty | 0:8efa2ed1bc48 | 43 | // |
Josahty | 0:8efa2ed1bc48 | 44 | // Here is the optional code for a software reset |
Josahty | 0:8efa2ed1bc48 | 45 | // reset = 0; |
Josahty | 0:8efa2ed1bc48 | 46 | // wait_us(1); |
Josahty | 0:8efa2ed1bc48 | 47 | // reset = 1; |
Josahty | 0:8efa2ed1bc48 | 48 | |
Josahty | 1:26e3d87d1f49 | 49 | //pb.mode(PullUp); |
Josahty | 0:8efa2ed1bc48 | 50 | |
Josahty | 0:8efa2ed1bc48 | 51 | // Set all 8 Port A bits to output direction |
Josahty | 1:26e3d87d1f49 | 52 | chip1.direction(PORT_A, 0x00); |
Josahty | 1:26e3d87d1f49 | 53 | chip2.direction(PORT_A, 0x00); |
Josahty | 0:8efa2ed1bc48 | 54 | // Set all 8 Port B bits to input direction |
Josahty | 1:26e3d87d1f49 | 55 | chip1.direction(PORT_B, 0xFF); |
Josahty | 1:26e3d87d1f49 | 56 | chip2.direction(PORT_B, 0xFF); |
Josahty | 0:8efa2ed1bc48 | 57 | // Start Loopback test sending out and reading back values |
Josahty | 0:8efa2ed1bc48 | 58 | // loopback test uses A0 and B0 pins - so use a wire to jumper those two pins on MCP23S17 together |
Josahty | 0:8efa2ed1bc48 | 59 | while (1) { |
Josahty | 1:26e3d87d1f49 | 60 | if(!(chip1.read(PORT_B) & 0x01)) { |
Josahty | 1:26e3d87d1f49 | 61 | chip1.write(PORT_A, 0x55); |
Josahty | 0:8efa2ed1bc48 | 62 | wait(.1); |
Josahty | 0:8efa2ed1bc48 | 63 | // read back value from MCP23S17 Port B and display B0 on mbed led1 |
Josahty | 1:26e3d87d1f49 | 64 | //led1 = 1; |
Josahty | 0:8efa2ed1bc48 | 65 | } |
Josahty | 0:8efa2ed1bc48 | 66 | // write 0xAA to MCP23S17 Port A |
Josahty | 1:26e3d87d1f49 | 67 | else { |
Josahty | 0:8efa2ed1bc48 | 68 | // write 0x55 to MCP23S17 Port A |
Josahty | 1:26e3d87d1f49 | 69 | chip1.write(PORT_A, 0xAA); |
Josahty | 0:8efa2ed1bc48 | 70 | wait(.1); |
Josahty | 0:8efa2ed1bc48 | 71 | // read back value from MCP23S17 Port B and display B0 on mbed led1 |
Josahty | 1:26e3d87d1f49 | 72 | //led1 = 0; |
Josahty | 0:8efa2ed1bc48 | 73 | // led1 should blink slowly when it is all working |
Josahty | 1:26e3d87d1f49 | 74 | } |
Josahty | 1:26e3d87d1f49 | 75 | |
Josahty | 1:26e3d87d1f49 | 76 | if((chip2.read(PORT_B) & 0x01)) { |
Josahty | 1:26e3d87d1f49 | 77 | chip2.write(PORT_A, 0x55); |
Josahty | 1:26e3d87d1f49 | 78 | wait(0.1); |
Josahty | 1:26e3d87d1f49 | 79 | led1 = 1; |
Josahty | 1:26e3d87d1f49 | 80 | } |
Josahty | 1:26e3d87d1f49 | 81 | else { |
Josahty | 1:26e3d87d1f49 | 82 | chip2.write(PORT_A, 0xAA); |
Josahty | 1:26e3d87d1f49 | 83 | wait(0.1); |
Josahty | 1:26e3d87d1f49 | 84 | led1 = 0; |
Josahty | 1:26e3d87d1f49 | 85 | } |
Josahty | 0:8efa2ed1bc48 | 86 | } |
Josahty | 0:8efa2ed1bc48 | 87 | } |