Diff: I2CEeprom.cpp

Revision:

1:b23f5561266c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/I2CEeprom.cpp	Sun Jul 19 09:34:04 2015 +0000
@@ -0,0 +1,198 @@
+/* Simple access class for I2C EEPROM chips like Microchip 24LC
+ * Copyright (c) 2015 Robin Hourahane
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "I2CEeprom.h"
+
+I2CEeprom::I2CEeprom(PinName sda, PinName scl, int address, size_t pageSize, size_t chipSize, int busSpeed):
+    m_i2c(sda, scl),
+    m_i2cAddress(address),
+    m_chipSize(chipSize),
+    m_pageSize(pageSize)
+{
+    m_i2c.frequency(busSpeed);
+}
+
+size_t I2CEeprom::read(size_t address, char &value) {
+    // Check the address and size fit onto the chip.
+    if (!checkSpace(address, 1))
+        return 0;
+        
+    char values[] = { (address >> 8), (address & 0xFF) };
+    if (m_i2c.write(m_i2cAddress, values, 2) == 0) {
+        if (m_i2c.read(m_i2cAddress, &value, 1) == 0) {
+            return 1;
+        }
+    }
+    
+    return 0;
+}
+
+size_t I2CEeprom::read(size_t address, char *buffer, size_t size) {
+    // Check the address and size fit onto the chip.
+    if (!checkSpace(address, size))
+        return 0;
+        
+    char values[] = { (address >> 8), (address & 0xFF) };
+    if (m_i2c.write(m_i2cAddress, values, 2) == 0) {
+        if (m_i2c.read(m_i2cAddress, buffer, size) == 0) {
+            return size;
+        }
+    }
+    
+    return 0;
+}
+
+size_t I2CEeprom::write(size_t address, char value) {
+    // Check the address and size fit onto the chip.
+    if (!checkSpace(address, 1))
+        return 0;
+        
+    char values[] = { (address >> 8), (address & 0xFF), value };
+    if (m_i2c.write(m_i2cAddress, values, 3) != 0) {
+        return 0;
+    }
+    
+    waitForWrite();
+    
+    return 1;
+}
+
+size_t I2CEeprom::write(size_t address, const char *buffer, size_t size) {
+    // Check the address and size fit onto the chip.
+    if (!checkSpace(address, size))
+        return 0;
+        
+    const char *page = buffer;
+    size_t left = size;
+    
+    // Whle we have some more data to write.
+    while (left != 0) {
+        // Calculate the number of bytes we can write in the current page.
+        // If the address is not page aligned then write enough to page 
+        // align it.
+        size_t toWrite;
+        if ((address % m_pageSize) != 0) {
+            toWrite = (((address / m_pageSize) + 1) * m_pageSize) - address;
+            if (toWrite > size) {
+                toWrite = size;
+            }
+        } else {
+            if (left <= m_pageSize) {
+                toWrite = left;
+            } else {
+                toWrite = m_pageSize;
+            }
+        }
+        
+        //printf("Writing [%.*s] at %d size %d\n\r", toWrite, page, address, toWrite);
+        // Start the page write with the addres ine one write call.
+        char values[] = { (address >> 8), (address & 0xFF) };
+        if (m_i2c.write(m_i2cAddress, values, 2, true) != 0) {
+            // Write failed to return bytes written so far.
+            return size - left;
+        }
+
+        // Write the bytes out one at a time to avoid having to copy them to
+        // another buffer.        
+        for (int count = 0; count != toWrite; ++count) {
+            if (m_i2c.write(*page) == 0) {
+            // Write failed to return bytes written so far.
+                return size - left;
+            }
+            ++page;
+        }
+        
+        // Stop the transaction now we've completed the page
+        // write.
+        m_i2c.stop();
+        
+        waitForWrite();
+        
+        // Update the counters with the amount we've just written
+        left -= toWrite;
+        address += toWrite;
+    }
+    
+    return size;
+}
+
+size_t I2CEeprom::fill(size_t address, char value, size_t size) {
+    // Check the address and size fit onto the chip.
+    if (!checkSpace(address, size))
+        return 0;
+        
+    size_t left = size;
+    
+    while (left != 0) {
+        size_t toWrite;
+        if ((address % m_pageSize) != 0) {
+            toWrite = (((address / m_pageSize) + 1) * 64) - address;
+            if (toWrite > size) {
+                toWrite = size;
+            }
+        } else {
+            if (left <= m_pageSize) {
+                toWrite = left;
+            } else {
+                toWrite = m_pageSize;
+            }
+        }
+        
+        //printf("Writing %d at %d size %d\n\r", value, address, toWrite);
+        char values[] = { (address >> 8), (address & 0xFF) };
+        if (m_i2c.write(m_i2cAddress, values, 2, true) != 0) {
+            return size - left;
+        }
+        
+        for (int count = 0; count != toWrite; ++count) {
+            if (m_i2c.write(value) == 0)
+                return size - left;
+        }
+        
+        m_i2c.stop();
+        
+        waitForWrite();
+        
+        left -= toWrite;
+        address += toWrite;
+    }
+    
+    return size;
+}
+
+void I2CEeprom::waitForWrite() {
+    // The chip doesn't ACK while writing to the actual EEPROM
+    // so loop trying to do a zero byte write until it is ACKed
+    // by the chip.
+    while (m_i2c.write(m_i2cAddress, 0, 0) != 0) {
+        // Wait for ack.
+        wait_ms(1);
+    }
+}
+
+bool I2CEeprom::checkSpace(size_t address, size_t size) {
+    // Only check if chip size is non-zero.
+    if (m_chipSize != 0) {
+        // Check that the address start in the chip and doesn't
+        // extend past.
+        if ((address >= m_chipSize) || ((address + size) >= m_chipSize))
+            return false;
+        else
+            return true;
+    }
+    
+    return true;
+}
+