Diff: Onewire.cpp

Revision:

8:5d0bd95b586f

Parent:

7:0a87f8c2d9e6

--- a/Onewire.cpp	Thu Oct 15 21:39:21 2015 +0000
+++ b/Onewire.cpp	Fri Oct 16 06:25:11 2015 +0000
@@ -17,20 +17,24 @@
     if (bit) 
     {
         // Write '1' bit
+        __disable_irq();
         oneBus_.output();
         oneBus_ = 0;
-        wait_us(12);
-        oneBus_.input();
-        wait_us(60);
+        wait_us(10);
+        oneBus_ = 1;
+        __enable_irq();        
+        wait_us(55);
     }
     else
     {
         // Write '0' bit
+        __disable_irq();
         oneBus_.output();
         oneBus_ = 0;
-        wait_us(60);
-        oneBus_.input();
-        wait_us(12);
+        wait_us(65);
+        oneBus_ = 1;
+        __enable_irq();        
+        wait_us(5);
     }
     __enable_irq();
 }
@@ -42,31 +46,45 @@
     __disable_irq();
     oneBus_.output();
     oneBus_ = 0;
-    wait_us(5);
+    wait_us(3);
     oneBus_.input();
-    wait_us(7);
+    wait_us(10);
     result = oneBus_.read();
-    wait_us(60);
     __enable_irq();
+    wait_us(53);
     return result;
 }
 
 int Onewire::init()
 {
+    // Ensure bus is high to start
+    oneBus_.input();
+    int MAX_RETRY_TEST_BUS_HIGH = 125;
+    for (int i = 0; i < MAX_RETRY_TEST_BUS_HIGH; i++)
+    {
+        if (oneBus_.read() == 1)
+            break;
+        wait_us(2);
+    }
+    if (oneBus_.read() != 1)
+        return ONEWIRE_FAIL_STUCK_LOW;
+    
+    // Pull LOW for 480us
+    __disable_irq();
     oneBus_.output();
     oneBus_ = 0;
+    __enable_irq();
     wait_us(480);
+    
+    // Allow to float and test to ensure presence of devices
+    // (which pull the bus low)
     __disable_irq();
     oneBus_.input();
-    wait_us(60);
-    if (oneBus_.read() == 0) 
-    {
-        __enable_irq();
-        wait_us(100);
-        return ONEWIRE_OK;
-    }
+    wait_us(70);
+    int readVal = oneBus_.read();
     __enable_irq();
-    return ONEWIRE_SEARCH_INIT_FAIL;
+    wait_us(410);
+    return (readVal == 0) ? ONEWIRE_OK : ONEWIRE_SEARCH_INIT_FAIL;
 }
 
 int Onewire::readByte() 
@@ -149,7 +167,6 @@
         
     // 1-Wire reset
     int initRslt = init();
-    wait_us(410);
     if (initRslt != ONEWIRE_OK)
     {
         // reset the search
@@ -236,10 +253,10 @@
     switch(errCode)
     {
         case ONEWIRE_OK: return "OK";
+        case ONEWIRE_FAIL_STUCK_LOW: return "Stuck Low";
         case ONEWIRE_SEARCH_ALL_DONE: return "All Done";
         case ONEWIRE_SEARCH_INIT_FAIL: return "Init Fail";
         case ONEWIRE_SEARCH_NOT_FOUND: return "Not Found";
-        case ONEWIRE_SEARCH_STUCK_HIGH: return "Stuck High";
         case ONEWIRE_SEARCH_COMP_BIT_ERR: return "Comp Bit Err";
     }
     return "Unknown Err";