v 0.4
Dependents: MCP23S17Test MCP23S17_Basic_IO_Demo HelloWorld Lab3-SnakeGame ... more
Revision 1:5abd129839e7, committed 2010-08-21
- Comitter:
- romilly
- Date:
- Sat Aug 21 07:05:21 2010 +0000
- Parent:
- 0:930da696072e
- Child:
- 2:6144709f1700
- Commit message:
- Added methods to set port directions, set outputd to either port and to read each port.
Changed in this revision
main.cpp | Show annotated file Show diff for this revision Revisions of this file |
--- a/main.cpp Wed Aug 18 12:30:39 2010 +0000 +++ b/main.cpp Sat Aug 21 07:05:21 2010 +0000 @@ -1,46 +1,88 @@ #include "mbed.h" -/* first attempt at driving an MCP23S17 -* -* Turns alternate bits of B register on and off +/* +* next baby step towards towards a library for MCP23S17 +* I'm proposing to allow 8-bit and 16-bit conditioning, reads, and writes +* and interrupt conditioning * -* I have not added many comments yet. -* This is a proof of concept, -* not a finished example. +* Unless someone asks for them, I'm not going to implement +* multi-reads or writes where a sequence of many bytes are read from or written +* to the same register +* +* This is currently experimental code. I'm still checking that I've understood the chip API. */ -DigitalOut myled(LED1); + +// all register addresses assume IOVCON.BANK = 0 (POR default) + +#define IODIRA 0x00 +#define IODIRB 0x01 +#define IOCON 0x0A +#define GPIOA 0x12 +#define GPIOB 0x13 +#define OLATA 0x14 +#define OLATB 0x15 + +// Control settings + +#define IOCON_BANK 0x80 // Banked registers +#define IOCON_BYTE_MODE 0x20 // Disables sequential operation. If bank = 0, operations toggle between A and B registers +#define IOCON_HAEN 0x08 // Hardware address enable SPI spi(p5, p6, p7); -DigitalOut ncs(p20); +DigitalOut ncs(p20); // not chip select; bring this low to enable the chip +char writeOpcode = 0x40; // A0, A1, A2 are tied to ground on the breadboard. +char readOpcode = writeOpcode | 1; // low order bit = 1 for read -void write(char command, char address, char data) { +void _write(char address, char data) { ncs = 0; - spi.write(command); + spi.write(writeOpcode); spi.write(address); spi.write(data); ncs = 1; } +char _read(char address) { + ncs = 0; + spi.write(readOpcode); + spi.write(address); + char result = spi.write(0); + ncs = 1; + return result; +} + void init() { - write(0x40, 0x0A, 0xA0); - write(0x40, 0x10, 0x00); + _write(IOCON, (IOCON_BYTE_MODE | IOCON_HAEN )); // Hardware addressing on, operations toggle between A and B registers } -void output(char byte) { - ncs = 0; - write(0x40,0x1A, byte); // configures for multi-write - could send a series of bytes for immediate output - ncs = 1; +void directionA(char direction) { + _write(IODIRA, direction); +} + +void directionB(char direction) { + _write(IODIRB, direction); +} + +void outputA(char byte) { + _write(OLATA, byte); +} + +void outputB(char byte) { + _write(OLATB, byte); +} + +char inputA() { + return _read(GPIOA); } int main() { init(); + directionA(0xFF); // all 8 bits set to input + directionB(0x00); // all 8 bits set to ouptut while(1) { - myled = 1; wait(0.2); - output(0xAA); - myled = 0; - wait(0.2); - output(0x55); + // copy inputs from A to outputs on B + outputB(inputA()); + } }