Diff: SoftI2C.cpp

Revision:

0:fee70b6fe0e9

Child:

1:05473196d133

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SoftI2C.cpp	Tue Nov 22 20:45:35 2016 +0000
@@ -0,0 +1,166 @@
+#include "SoftI2C.h"
+
+SoftI2C::SoftI2C(PinName sda, PinName scl) : _sda(sda), _scl(scl) {
+    // Set defaults
+    _sda.mode(PullNone);
+    _scl.mode(PullNone);
+    _sda.input();
+    _scl.input();
+    frequency(100000);
+    
+    active = false;
+    
+    }
+    
+void SoftI2C::frequency(int hz) {
+    delay_us = 1000000 / hz / 4; //delay is a quarter of the total period
+}
+
+int SoftI2C::read(int address, char *data, int length, bool repeated) {
+    start();
+    
+    // Write address with LSB to one
+    if (write(address | 0x01) == 0) {
+        return 1;
+    }  
+    
+    // Read the data
+    for(int i = 0; i<length - 1; i++) {
+        data[i] = read(1);
+    }
+    data[length-1] = read(0);
+    
+    if (repeated == false) {
+        stop();
+    }
+    return 0;
+}
+
+int SoftI2C::write(int address, const char *data, int length, bool repeated) {
+    start();
+    
+    // Write address with LSB to zero
+    if (write(address & 0xFE) == 0) {
+        return 1;
+    }  
+    
+    // Write the data
+    for(int i = 0; i<length; i++) {
+        if(write(data[i]) == 0) {
+            return 1;
+        }
+    }
+    
+    if (repeated == false) {
+        stop();
+    }
+    return 0;
+}
+
+int SoftI2C::read(int ack) {
+    int retval = 0;
+    
+    // Shift the bits out, msb first
+    for (int i = 7; i>=0; i--) {
+        //SCL low
+        _scl.output();
+        _scl.write(0);
+        _sda.input();
+        wait_us(delay_us);
+        
+        //read SDA
+        retval |= _sda.read() << i;
+        wait_us(delay_us);
+        
+        //SCL high again
+        _scl.input();
+        wait_us(delay_us << 1); //wait two delays
+    }
+    
+    // Last cycle to set the ACK
+    _scl.output();
+    _scl.write(0);
+    if ( ack ) {
+        _sda.output();
+        _sda.write(0);
+    } else {
+        _sda.input();
+    }
+    wait_us(delay_us << 1);
+    
+    _scl.input();
+    wait_us(delay_us << 1);
+
+    
+    return retval;
+}
+
+int SoftI2C::write(int data) {
+    // Shift the bits out, msb first
+    for (int i = 7; i>=0; i--) {
+        //SCL low
+        _scl.output();
+        _scl.write(0);
+        wait_us(delay_us);
+        
+        //Change SDA depending on the bit
+        if ( (data >> i) & 0x01 ) {
+            _sda.input();
+        } else {
+            _sda.output();
+            _sda.write(0);
+        }
+        wait_us(delay_us);
+        
+        //SCL high again
+        _scl.input();
+        wait_us(delay_us << 1); //wait two delays
+    }
+    
+    // Last cycle to get the ACK
+    _scl.output();
+    _scl.write(0);
+    wait_us(delay_us);
+    
+    _sda.input();
+    wait_us(delay_us);
+    
+    _scl.input();
+    wait_us(delay_us);
+    int retval = ~_sda.read(); //Read the ack
+    wait_us(delay_us);
+    
+    return retval;
+}
+
+void SoftI2C::start(void) {
+    if (active) { //if repeated start
+        //Set SDA high, toggle scl
+        _sda.input();
+        _scl.output();
+        _scl.write(0);
+        wait_us(delay_us << 1);
+        _scl.input();
+        wait_us(delay_us << 1);
+    }
+    // Pull SDA low
+    _sda.output();
+    _sda.write(0);
+    wait_us(delay_us);
+    active = true;
+}
+
+void SoftI2C::stop(void) {
+    // Float SDA high
+    _scl.output();
+    _scl.write(0);
+    _sda.output();
+    _sda.write(0);
+    wait_us(delay_us);
+    _scl.input();
+    wait_us(delay_us);
+    _sda.input();
+    wait_us(delay_us);
+    
+    active = false;
+}
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