Revision 1:70e1ebe47253, committed 2011-01-28

Comitter:

4180_1

Date:

Fri Jan 28 01:44:27 2011 +0000

Parent:

0:12f4911d7ba0

Child:

2:934a0500abde

Commit message:

Changed in this revision

--- a/main.cpp	Thu Jan 27 03:16:18 2011 +0000
+++ b/main.cpp	Fri Jan 28 01:44:27 2011 +0000
@@ -22,16 +22,22 @@
 // mbed p20 is connected to ~chipSelect on the MCP23S17
 MCP23S17 chip = MCP23S17(spi, p20, writeOpcode);
 
+// Optional software reset - mbed p20 to MCP23S17 reset pin
+// DigitalOut reset(p20);
+
 DigitalOut led1(LED1); // mbed LED1 is used for test status display
 
 int main() {
-//  Nothing has to be connected to the MCP23S17 reset pin since it has a power on reset circuit.
-//  It can be used for a software forced reset by pulling it low with an mbed GPIO pin.
-//  But just leave it unconnected for this simple demo code. It is possible to lock up the chip
-//  if you happen to reset the mbed in the middle of an SPI transfer (not too likely). 
-//  If it happens just remove and attach the USB cable to reset by cycling the power.
+//  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