Make MCP23s17 reset pin optional

[wollewald]

Make MCP23s17 reset pin optional

[wollewald]

If you don't pass the reset pin, 99 will be applied now.

[wollewald]

The reset pin of the mcp23s17 is pin no 18. The reset pin is only used in init() to ensure that all registers are set to default if you upload a new sketch without disconnecting from power. What I have implemented a week ago and not yet documented is a software reset. If you pass a reset pin with a number >= 99 the software reset will carried out instead of the hardware reset. Like this:

#define RESET_PIN 99
#define MCP_ADDRESS 0x20 // (A2/A1/A0 = LOW)
MCP23S17 myMCP = MCP23S17(CS_PIN, RESET_PIN, MCP_ADDRESS);

The software reset just sets all registers to default values by SPI/I2C commands.
If you don't connect the reset pin to a real pin, then you should connect it to HIGH level.

[thijstriemstra]

Thanks for the feedback. An additional mcp23s17 constructor where reset_pin = 99 would be nice. Tested with 99 (instead of 27) and everything seems to work ok.