Diff: one_wire.cpp

Revision:

0:53f05303850a

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/one_wire.cpp	Mon Dec 31 12:08:24 2012 +0000
@@ -0,0 +1,114 @@
+#include "one_wire.h"
+
+/* "borrowed" from snatch59: OneWireCRC and simplified for my needs */
+ 
+const int timing[] = {6, 64, 60, 10, 9, 55, 0, 480, 70, 410};
+ 
+OneWire::OneWire(PinName pin) : port(pin) {
+}
+ 
+int OneWire::reset() {
+    int result = 0;    // sample presence pulse result
+        
+    wait_us(timing[6]);
+    port.output();
+    port = 0;
+    wait_us(timing[7]);
+    port.input();
+    wait_us(timing[8]);
+    result = !(port & 0x01);
+    wait_us(timing[9]);
+    
+    return result;
+}
+ 
+void OneWire::write_bit(int bit) {
+    bit = bit & 0x01;
+    
+    if (bit) {
+        // Write '1' bit
+        port.output();
+        port = 0;
+        wait_us(timing[0]);
+        port.input();
+        wait_us(timing[1]);
+    } else {
+        // Write '0' bit
+        port.output();
+        port = 0;
+        wait_us(timing[2]);
+        port.input();
+        wait_us(timing[3]);
+    }
+}
+ 
+int OneWire::read_bit() {
+    int result;
+    
+    port.output();
+    port = 0;
+    wait_us(timing[0]);
+    port.input();
+    wait_us(timing[4]);
+    result = port & 0x01;
+    wait_us(timing[5]);
+       
+    return result;
+}
+ 
+void OneWire::write_byte(int data) {
+    // Loop to write each bit in the byte, LS-bit first
+    for (int loop = 0; loop < 8; loop++) {
+        write_bit(data & 0x01);
+        
+        // shift the data byte for the next bit
+        data >>= 1;
+    }
+}
+ 
+int OneWire::read_byte() {
+    int result = 0;
+    
+    for (int loop = 0; loop < 8; loop++) {
+        // shift the result to get it ready for the next bit
+        result >>= 1;
+        
+        // if result is one, then set MS bit
+        if (read_bit()) result |= 0x80;
+    }
+    
+    return result;
+}
+ 
+void OneWire::block(char* data, int data_len) {
+    for (int loop = 0; loop < data_len; loop++) {
+        data[loop] = read_byte(); // original: touchByte(data[loop]);
+    }
+}
+
+void OneWire::prepare_read() {
+    reset();
+    write_byte(SKIP_ROM);
+    write_byte(CONVERT);
+
+    // switch on parasite power while waiting.
+    port.output();
+    port = 1;
+}
+
+int OneWire::read_temperature() {
+    char data[9];
+    short *raw_temp = (short *) data;
+    int temperature = -99;
+    
+    reset();
+    write_byte(SKIP_ROM);
+    write_byte(READSCRATCH);
+    block(data, 9);
+    
+    if (data[5] == 255 && data[7] == 16) {
+        temperature = *raw_temp >> 4;
+    }
+    
+    return temperature;
+}