Diff: main.cpp

Revision:

0:b91b5753e54f

Child:

1:ea045d9d4c5b

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sat Aug 06 11:31:15 2011 +0000
@@ -0,0 +1,91 @@
+#include "mbed.h"
+
+// MCP4141. 2.7 to 5.5V 7-bit linear digital potentiometer with SPI interface.
+// Wiper commands can be write or read. This program is to write commands only.
+// MOSI/MISO are multiplexed in the MCP4141 side.
+
+// Author: Lluis Nadal. August 2011.
+
+
+DigitalOut leds[] = {(LED1), (LED2),(LED3),(LED4)};
+
+//Define SPI mBed side:
+SPI spi(p5, p6, p7); // mosi, miso, sclk. To write commands only, you do not need to connect p6(miso) to MCP4141.
+DigitalOut cs(p8); // Chip select. Active low.
+
+/*
+MCP4141 side:
+p8 = Vdd: +3.3V. p4 = Vss: GROUND. p1: cs (mBed's p8).
+p2: sclk (mBed's p7). p3: SDI (mBed's p5). p5: potentiometer a. p7: potentiometer b.
+Rab: 5k, 10k 50k or 100k options. p6: wiper (75 Ohm).
+Attach ohmeter to pins p5 and p7.
+*/
+
+void write(int n) { // 0 >= n <= 128
+    cs=1;
+    cs=0;
+    spi.write(0x00); // Address(volatile) 0000, write=00, data=00 = 0x00
+    spi.write(n); // Data 
+    cs=1;
+}
+
+void increment() {
+    cs=1;
+    cs=0;
+    spi.write(0x07);// Address(volatile) 0000, increment 0100 = 0x07
+    cs=1;
+}
+
+void decrement() {
+    cs=0;
+    spi.write(0x0B);// Address(volatile) 0000, decrement 1000 = 0x0B
+    cs=1;
+}
+
+
+
+int main() {
+
+    cs=1; // Disables MCP4141
+
+    spi.format(8,0); // 8 bits , mode 0
+    spi.frequency(1000000); // Default SPI frequency. ( 250kHz maximum for read commands).
+
+    while (1) {
+
+        leds[0]=0;
+        leds[1]=0;
+        leds[2]=0;
+        leds[3]=0; // All leds off.
+        wait(1);
+        
+        write(32);// Set wiper to 32/128 = 1/4 Rab
+        leds[0]=1;
+        wait(4);
+
+        write(64);// Set wiper to 64/128 = 1/2 Rab
+        leds[1]=1;
+        wait(4);
+
+        write(96);// Set wiper to 96/128 = 3/4 Rab
+        leds[2]=1;
+        wait(4);
+
+        // Decrement wiper 10 times
+        for (int i=0; i<10; i++) {
+            decrement();
+        }
+        leds[3]=1;
+        wait(4);
+
+        // Increment wiper 10 times
+        for (int i=0; i<10; i++) {
+            increment();
+        }
+
+        leds[3]=0;
+        wait(4);
+
+    }
+
+}