I2CEEBlockDevice.cpp

00001 /* Simple access class for I2C EEPROM chips like Microchip 24LC
00002  * Copyright (c) 2015 Robin Hourahane
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 #include "I2CEEBlockDevice.h"
00017 
00018 #define I2CEE_TIMEOUT 10000
00019  
00020 
00021 I2CEEBlockDevice::I2CEEBlockDevice(
00022         PinName sda, PinName scl, uint8_t addr,
00023         bd_size_t size, bd_size_t block, int freq)
00024     : _i2c(sda, scl), _i2c_addr(addr), _size(size), _block(block)
00025 {
00026     _i2c.frequency(freq);
00027 }
00028 
00029 int I2CEEBlockDevice::init()
00030 {
00031     return _sync();
00032 }
00033 
00034 int I2CEEBlockDevice::deinit()
00035 {
00036     return 0;
00037 }
00038 
00039 int I2CEEBlockDevice::read(void *buffer, bd_addr_t addr, bd_size_t size)
00040 {
00041     // Check the address and size fit onto the chip.
00042     MBED_ASSERT(is_valid_read(addr, size));
00043 
00044     _i2c.start();
00045     if (!_i2c.write(_i2c_addr | 0) ||
00046         !_i2c.write((char)(addr >> 8)) ||
00047         !_i2c.write((char)(addr & 0xff))) {
00048         return BD_ERROR_DEVICE_ERROR;
00049     }
00050     _i2c.stop();
00051 
00052     if (_i2c.read(_i2c_addr, static_cast<char*>(buffer), size) < 0) {
00053         return BD_ERROR_DEVICE_ERROR;
00054     }
00055 
00056     return 0;
00057 }
00058  
00059 int I2CEEBlockDevice::program(const void *buffer, bd_addr_t addr, bd_size_t size)
00060 {
00061     // Check the addr and size fit onto the chip.
00062     MBED_ASSERT(is_valid_program(addr, size));
00063         
00064     // While we have some more data to write.
00065     while (size > 0) {
00066         uint32_t off = addr % _block;
00067         uint32_t chunk = (off + size < _block) ? size : (_block - off);
00068 
00069         _i2c.start();
00070         if (!_i2c.write(_i2c_addr | 0) ||
00071             !_i2c.write((char)(addr >> 8)) ||
00072             !_i2c.write((char)(addr & 0xff))) {
00073             return BD_ERROR_DEVICE_ERROR;
00074         }
00075 
00076         for (unsigned i = 0; i < chunk; i++) {
00077             _i2c.write(static_cast<const char*>(buffer)[i]);
00078         }
00079         _i2c.stop();
00080 
00081         int err = _sync();
00082         if (err) {
00083             return err;
00084         }
00085 
00086         addr += chunk;
00087         size -= chunk;
00088         buffer = static_cast<const char*>(buffer) + chunk;
00089     }
00090 
00091     return 0;
00092 }
00093 
00094 int I2CEEBlockDevice::erase(bd_addr_t addr, bd_size_t size)
00095 {
00096     // No erase needed
00097     return 0;
00098 }
00099 
00100 int I2CEEBlockDevice::_sync()
00101 {
00102     // The chip doesn't ACK while writing to the actual EEPROM
00103     // so loop trying to do a zero byte write until it is ACKed
00104     // by the chip.
00105     for (int i = 0; i < I2CEE_TIMEOUT; i++) {
00106         if (_i2c.write(_i2c_addr | 0, 0, 0) < 1) {
00107             return 0;
00108         }
00109 
00110         wait_ms(1);
00111     }
00112 
00113     return BD_ERROR_DEVICE_ERROR;
00114 }
00115  
00116 bd_size_t I2CEEBlockDevice::get_read_size() const
00117 {
00118     return 1;
00119 }
00120 
00121 bd_size_t I2CEEBlockDevice::get_program_size() const
00122 {
00123     return 1;
00124 }
00125 
00126 bd_size_t I2CEEBlockDevice::get_erase_size() const
00127 {
00128     return 1;
00129 }
00130 
00131 bd_size_t I2CEEBlockDevice::size() const
00132 {
00133     return _size;
00134 }