Diff: main.cpp

Revision:

0:875a9fb3e4cf

Child:

1:627579b6dc90

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri Jan 23 11:09:32 2015 +0000
@@ -0,0 +1,123 @@
+#include "mbed.h"
+ 
+// 24AA02E48 datasheet:
+// http://ww1.microchip.com/downloads/en/DeviceDoc/20002124E.pdf
+ 
+// the address of the EEPROM I2C device
+#define EEPROM_24AA02E48_ADDR (0xA0)
+ 
+static I2C i2c(P0_27, P0_28);
+ 
+int main(void) {
+ 
+    int i = 0;
+    char offset = 0;
+    bool verifiedOk = true;
+    char buf[7];
+ 
+    printf("Reading MAC address\n");
+ 
+    do {
+ 
+        // the MAC address is stored at offset 0xFA in the EEPROM
+        // start by telling the EEPROM that we want to access this offset
+        offset = 0xFA;
+ 
+        // write returns non-0 on failure
+        if (i2c.write(EEPROM_24AA02E48_ADDR, &offset, 1) != 0) {
+            printf("Failed to write to I2C device (%x) at offset 0xFA\n",
+                    EEPROM_24AA02E48_ADDR);
+            break;
+        }
+ 
+        // read the MAC address (48 bits = 6 bytes). The read function
+        // returns non-0 in case of failure
+        if (i2c.read(EEPROM_24AA02E48_ADDR, buf, 6) != 0) {
+            printf("Failed to read from I2C device (%x) at offset 0xFA\n",
+                    EEPROM_24AA02E48_ADDR);
+        }
+ 
+        printf(" - the MAC address is %02X:%02X:%02X:%02X:%02X:%02X\n",
+                buf[0],buf[1],buf[2],buf[3],buf[4],buf[5]);
+ 
+    } while (0);
+ 
+    printf("Writing data to EEPROM\n");
+ 
+    do {
+ 
+        // initializing the buffer with values that will be
+        // written to the EEPROM. Note that index 0 is used as
+        // the offset and data are put in the remaining 6 bytes
+        // see "write data" section below
+        for (i = 0; i < 6; i++) {
+            buf[i+1] = i+3;
+        }
+ 
+        // We write to the beginning of the EEPROM (offset = 0) in this
+        // example.
+        //
+        // Please note that there are limitations to how to write to the EEPROM
+        // - At most one page (8 bytes for this EEPROM) can be written at a time
+        // - A write request will wrap around if writing passed a page boundary
+        //   - Example: If writing 4 bytes starting at offset 6, positions 6,7
+        //              0, and 1 will actually be written since page boundaries
+        //              are at even page sizes (0, 8, 16, ...) and a write
+        //              request will wrap around if passing a page boundary.
+        // - the upper part (0x80-0xFF) are always write protected for this
+        //   particular EEPROM
+        offset = 0;
+ 
+ 
+        // write data
+        // All data is written in one request (page write). The first byte must
+        // therefore contain the offset to where the data should be written.
+        // It is also possible to write one byte at a time.
+        buf[0] = offset;
+        if (i2c.write(EEPROM_24AA02E48_ADDR, buf, 7) != 0) {
+            printf("Failed to write to I2C device (%x) 2\n",
+                    EEPROM_24AA02E48_ADDR);
+            break;
+        }
+ 
+ 
+    } while (0);
+ 
+    printf("Reading back written data\n");
+ 
+    do {
+        // resetting the buffer
+        memset(buf, 0, 6);
+ 
+ 
+        // tell the EEPROM which offset to use
+        if (i2c.write(EEPROM_24AA02E48_ADDR, &offset, 1) != 0) {
+            printf("Failed to write to I2C device (%x) 3\n",
+                    EEPROM_24AA02E48_ADDR);
+            break;
+        }
+ 
+        // read data
+        if (i2c.read(EEPROM_24AA02E48_ADDR, buf, 6) != 0) {
+            printf("Failed to read from I2C device (%x) 3\n",
+                    EEPROM_24AA02E48_ADDR);
+        }
+ 
+        // verifying read data
+        for (i = 0; i < 6; i++) {
+            if (buf[i] != (i+3)) {
+                verifiedOk = false;
+                printf(" - Read data not equal to written buf[%d]=%d != %d\n",
+                        i, buf[i], (i+3));
+                break;
+            }
+        }
+ 
+        if (verifiedOk) {
+            printf(" - Read data is equal to written data\n");
+        }
+ 
+    } while (0);
+ 
+    return 0;
+}