Revision 0:b0247e85bf0e, committed 2014-12-07

Comitter:

karelv

Date:

Sun Dec 07 13:56:12 2014 +0000

Commit message:

IO-based I2C function, to show my HW is correctly wired

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Dec 07 13:56:12 2014 +0000
@@ -0,0 +1,30 @@
+#include "mbed.h"
+#include "my_i2c.h"
+
+DigitalOut myled(LED1);
+
+// Connections made:
+// SDA to pin9  of LPC4088 QSB
+// SCL to pin10 of LPC4088 QSB
+// on I2C bus is PCF8574 connected at sub-address 0 (0x40).
+// all supplied at 3.3V
+// no external pullup (5K internal pullup used by my_i2c functions)
+// 
+// note in the my_i2c functions a delay of 1us is added after each transition of the pin.
+//      so this means an absolute maximum frequency of 500kHz.
+
+int main() {
+    
+    while(1) {
+        myled = 1;
+        my_i2cStart(0x40);
+        my_i2cWrite (0x55);
+        my_i2cStop();
+        wait(0.5);
+        myled = 0;
+        my_i2cStart(0x40);
+        my_i2cWrite (0xAA);
+        my_i2cStop();
+        wait(0.5);
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Sun Dec 07 13:56:12 2014 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/4fc01daae5a5
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/my_i2c.cpp	Sun Dec 07 13:56:12 2014 +0000
@@ -0,0 +1,192 @@
+#include "mbed.h"
+#include "my_i2c.h"
+
+DigitalInOut sda(p9);
+DigitalInOut scl(p10);
+
+
+#define SDA(state) if (state) { \
+  sda.input ();                 \
+  sda = 1;                      \
+} else {                        \
+  sda = 0;                      \
+  sda.output ();                \
+}
+
+#define SCL(state) if (state) { \
+  scl.input ();                 \
+  scl = 1;                      \
+} else {                        \
+  scl = 0;                      \
+  scl.output ();                \
+}
+
+#define IO_DELAY() wait_us (1)
+
+
+void my_i2cWriteByte (unsigned char byte);
+bool my_i2cGetAck ();
+unsigned char my_i2cReadByte ();
+
+
+bool
+my_i2cStart (unsigned char slaveAddress)
+{
+  SDA(1);
+  SCL(1);
+  IO_DELAY();
+  SDA(0);
+  IO_DELAY();
+
+  my_i2cWriteByte (slaveAddress);
+
+  return my_i2cGetAck ();
+}
+
+
+bool
+my_i2cStop ()
+{
+  SDA(0);
+  SCL(0);
+  IO_DELAY();
+
+  SCL(1);
+  IO_DELAY();
+
+  SDA(1);
+  IO_DELAY();
+
+  return true;
+}
+
+
+bool
+my_i2cRepeatedStart (unsigned char slaveAddress)
+{
+  SCL(0);
+  IO_DELAY();
+
+  SDA(1);
+
+  IO_DELAY();
+
+  SCL(1);
+
+  IO_DELAY();
+
+  SDA(0);
+  my_i2cWriteByte (slaveAddress);
+
+  return my_i2cGetAck ();
+}
+
+
+bool
+my_i2cWrite (unsigned char data)
+{
+  my_i2cWriteByte (data);
+  return my_i2cGetAck ();
+}
+
+
+unsigned char
+my_i2cReadByte ()
+{
+  unsigned char data = 0;
+
+  for (int i = 0x80; i > 0x00; i >>= 1)
+  {
+    SCL(0);
+    SDA(1);
+    IO_DELAY();
+
+    SCL(1);
+    IO_DELAY();
+
+    if (sda)
+    { // turn bit to 1...
+      data |= i;
+    }
+  }
+  return data;
+}
+
+
+unsigned char
+my_i2cReadAck ()
+{
+  unsigned char data = my_i2cReadByte ();
+
+  SCL(0);
+  SDA(0);
+  IO_DELAY();
+
+  SCL(1);
+
+  // wait till scl is high
+  IO_DELAY();
+
+  return data;
+}
+
+
+unsigned char
+my_i2cReadNak ()
+{
+  unsigned char data = my_i2cReadByte ();
+
+  SCL(0);
+  SDA(1);
+  IO_DELAY();
+
+  SCL(1);
+  // wait till scl is high
+  IO_DELAY();
+
+  return data;
+}
+
+
+unsigned char
+my_i2cRead (unsigned char ack)
+{
+  if (ack)
+  {
+    return my_i2cReadAck ();
+  }
+  return my_i2cReadNak ();
+}
+
+
+void
+my_i2cWriteByte (unsigned char byte)
+{
+  for (int i = 0x80; i > 0x00; i >>= 1)
+  {
+    SCL(0);
+    SDA((byte & i) ? true : false);
+    IO_DELAY();
+
+    SCL(1);
+    IO_DELAY();
+  }
+}
+
+
+bool
+my_i2cGetAck ()
+{
+  SCL(0);
+  SDA(1);
+  IO_DELAY();
+
+  SCL(1);
+// wait till clock = 1...
+  IO_DELAY();
+
+  bool ack = false;
+  ack = sda;
+
+  return !ack;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/my_i2c.h	Sun Dec 07 13:56:12 2014 +0000
@@ -0,0 +1,15 @@
+#ifndef __MY_I2C_H__
+#define __MY_I2C_H__
+
+bool my_i2cStart (unsigned char slaveAddress);
+bool my_i2cStop ();
+bool my_i2cRepeatedStart (unsigned char slaveAddress);
+bool my_i2cWrite (unsigned char data);
+unsigned char my_i2cReadByte ();
+unsigned char my_i2cReadAck ();
+unsigned char my_i2cReadNak ();
+unsigned char my_i2cRead (unsigned char ack);
+void my_i2cWriteByte (unsigned char byte);
+bool my_i2cGetAck ();
+
+#endif // __MY_I2C_H__