i2c_api.c

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2006-2013 ARM Limited
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 "i2c_api.h"
00017 #include "cmsis.h"
00018 #include "pinmap.h"
00019 #include "error.h"
00020 
00021 static const PinMap PinMap_I2C_SDA[] = {
00022     {P0_0 , I2C_1, 3},
00023     {P0_10, I2C_2, 2},
00024     {P0_19, I2C_1, 3},
00025     {P0_27, I2C_0, 1},
00026     {NC   , NC   , 0}
00027 };
00028 
00029 static const PinMap PinMap_I2C_SCL[] = {
00030     {P0_1 , I2C_1, 3},
00031     {P0_11, I2C_2, 2},
00032     {P0_20, I2C_1, 3},
00033     {P0_28, I2C_0, 1},
00034     {NC   , NC,    0}
00035 };
00036 
00037 #define I2C_CONSET(x)       (x->i2c->I2CONSET)
00038 #define I2C_CONCLR(x)       (x->i2c->I2CONCLR)
00039 #define I2C_STAT(x)         (x->i2c->I2STAT)
00040 #define I2C_DAT(x)          (x->i2c->I2DAT)
00041 #define I2C_SCLL(x, val)    (x->i2c->I2SCLL = val)
00042 #define I2C_SCLH(x, val)    (x->i2c->I2SCLH = val)
00043 
00044 static const uint32_t I2C_addr_offset[2][4] = {
00045     {0x0C, 0x20, 0x24, 0x28},
00046     {0x30, 0x34, 0x38, 0x3C}
00047 };
00048 
00049 static inline void i2c_conclr(i2c_t *obj, int start, int stop, int interrupt, int acknowledge) {
00050     I2C_CONCLR(obj) = (start << 5)
00051                     | (stop << 4)
00052                     | (interrupt << 3)
00053                     | (acknowledge << 2);
00054 }
00055 
00056 static inline void i2c_conset(i2c_t *obj, int start, int stop, int interrupt, int acknowledge) {
00057     I2C_CONSET(obj) = (start << 5)
00058                     | (stop << 4)
00059                     | (interrupt << 3)
00060                     | (acknowledge << 2);
00061 }
00062 
00063 // Clear the Serial Interrupt (SI)
00064 static inline void i2c_clear_SI(i2c_t *obj) {
00065     i2c_conclr(obj, 0, 0, 1, 0);
00066 }
00067 
00068 static inline int i2c_status(i2c_t *obj) {
00069     return I2C_STAT(obj);
00070 }
00071 
00072 // Wait until the Serial Interrupt (SI) is set
00073 static int i2c_wait_SI(i2c_t *obj) {
00074     int timeout = 0;
00075     while (!(I2C_CONSET(obj) & (1 << 3))) {
00076         timeout++;
00077         if (timeout > 100000) return -1;
00078     }
00079     return 0;
00080 }
00081 
00082 static inline void i2c_interface_enable(i2c_t *obj) {
00083     I2C_CONSET(obj) = 0x40;
00084 }
00085 
00086 static inline void i2c_power_enable(i2c_t *obj) {
00087     switch ((int)obj->i2c) {
00088         case I2C_0: LPC_SC->PCONP |= 1 << 7; break;
00089         case I2C_1: LPC_SC->PCONP |= 1 << 19; break;
00090         case I2C_2: LPC_SC->PCONP |= 1 << 26; break;
00091     }
00092 }
00093 
00094 void i2c_init(i2c_t *obj, PinName sda, PinName scl) {
00095     // determine the SPI to use
00096     I2CName i2c_sda = (I2CName)pinmap_peripheral(sda, PinMap_I2C_SDA);
00097     I2CName i2c_scl = (I2CName)pinmap_peripheral(scl, PinMap_I2C_SCL);
00098     obj->i2c = (LPC_I2C_TypeDef *)pinmap_merge(i2c_sda, i2c_scl);
00099     
00100     if ((int)obj->i2c == NC) {
00101         error("I2C pin mapping failed");
00102     }
00103     
00104     // enable power
00105     i2c_power_enable(obj);
00106     
00107     // set default frequency at 100k
00108     i2c_frequency(obj, 100000);
00109     i2c_conclr(obj, 1, 1, 1, 1);
00110     i2c_interface_enable(obj);
00111     
00112     pinmap_pinout(sda, PinMap_I2C_SDA);
00113     pinmap_pinout(scl, PinMap_I2C_SCL);
00114 }
00115 
00116 inline int i2c_start(i2c_t *obj) {
00117     int status = 0;
00118     // 8.1 Before master mode can be entered, I2CON must be initialised to:
00119     //  - I2EN STA STO SI AA - -
00120     //  -  1    0   0   0  x - -
00121     // if AA = 0, it can't enter slave mode
00122     i2c_conclr(obj, 1, 1, 1, 1);
00123     
00124     // The master mode may now be entered by setting the STA bit
00125     // this will generate a start condition when the bus becomes free
00126     i2c_conset(obj, 1, 0, 0, 1);
00127     
00128     i2c_wait_SI(obj);
00129     status = i2c_status(obj);
00130     
00131     // Clear start bit now transmitted, and interrupt bit
00132     i2c_conclr(obj, 1, 0, 0, 0);
00133     return status;
00134 }
00135 
00136 inline int i2c_stop(i2c_t *obj) {
00137     // write the stop bit
00138     i2c_conset(obj, 0, 1, 0, 0);
00139     i2c_clear_SI(obj);
00140     
00141     // wait for STO bit to reset
00142     int timeout = 0;
00143     while (I2C_CONSET(obj) & (1 << 4)){
00144         timeout++;
00145         if(timeout > 10000) return -1;
00146     }
00147     return 0;
00148 }
00149 
00150 static inline int i2c_do_write(i2c_t *obj, int value, uint8_t addr) {
00151     // write the data
00152     I2C_DAT(obj) = value;
00153     
00154     // clear SI to init a send
00155     i2c_clear_SI(obj);
00156     
00157     // wait and return status
00158     i2c_wait_SI(obj);
00159     return i2c_status(obj);
00160 }
00161 
00162 static inline int i2c_do_read(i2c_t *obj, int last) {
00163     // we are in state 0x40 (SLA+R tx'd) or 0x50 (data rx'd and ack)
00164     if (last) {
00165         i2c_conclr(obj, 0, 0, 0, 1); // send a NOT ACK
00166     } else {
00167         i2c_conset(obj, 0, 0, 0, 1); // send a ACK
00168     }
00169     
00170     // accept byte
00171     i2c_clear_SI(obj);
00172     
00173     // wait for it to arrive
00174     i2c_wait_SI(obj);
00175     
00176     // return the data
00177     return (I2C_DAT(obj) & 0xFF);
00178 }
00179 
00180 void i2c_frequency(i2c_t *obj, int hz) {
00181     // [TODO] set pclk to /4
00182     uint32_t PCLK = SystemCoreClock / 4;
00183     
00184     uint32_t pulse = PCLK / (hz * 2);
00185     
00186     // I2C Rate
00187     I2C_SCLL(obj, pulse);
00188     I2C_SCLH(obj, pulse);
00189 }
00190 
00191 // The I2C does a read or a write as a whole operation
00192 // There are two types of error conditions it can encounter
00193 //  1) it can not obtain the bus
00194 //  2) it gets error responses at part of the transmission
00195 //
00196 // We tackle them as follows:
00197 //  1) we retry until we get the bus. we could have a "timeout" if we can not get it
00198 //      which basically turns it in to a 2)
00199 //  2) on error, we use the standard error mechanisms to report/debug
00200 //
00201 // Therefore an I2C transaction should always complete. If it doesn't it is usually
00202 // because something is setup wrong (e.g. wiring), and we don't need to programatically
00203 // check for that
00204 int i2c_read(i2c_t *obj, int address, char *data, int length, int stop) {
00205     int count, status;
00206     
00207     status = i2c_start(obj);
00208     
00209     if ((status != 0x10) && (status != 0x08)) {
00210         i2c_stop(obj);
00211         return status;
00212     }
00213     
00214     status = i2c_do_write(obj, (address | 0x01), 1);
00215     if (status != 0x40) {
00216         i2c_stop(obj);
00217         return status;
00218     }
00219     
00220     // Read in all except last byte
00221     for (count = 0; count < (length - 1); count++) {
00222         int value = i2c_do_read(obj, 0);
00223         status = i2c_status(obj);
00224         if (status != 0x50) {
00225             i2c_stop(obj);
00226             return status;
00227         }
00228         data[count] = (char) value;
00229     }
00230     
00231     // read in last byte
00232     int value = i2c_do_read(obj, 1);
00233     status = i2c_status(obj);
00234     if (status != 0x58) {
00235         i2c_stop(obj);
00236         return status;
00237     }
00238     
00239     data[count] = (char) value;
00240     
00241     // If not repeated start, send stop.
00242     if (stop) {
00243         i2c_stop(obj);
00244     }
00245     
00246     return 0;
00247 }
00248 
00249 int i2c_write(i2c_t *obj, int address, const char *data, int length, int stop) {
00250     int i, status;
00251     
00252     status = i2c_start(obj);
00253     
00254     if ((status != 0x10) && (status != 0x08)) {
00255         i2c_stop(obj);
00256         return status;
00257     }
00258     
00259     status = i2c_do_write(obj, (address & 0xFE), 1);
00260     if (status != 0x18) {
00261         i2c_stop(obj);
00262         return status;
00263     }
00264     
00265     for (i=0; i<length; i++) {
00266         status = i2c_do_write(obj, data[i], 0);
00267         if (status != 0x28) {
00268             i2c_stop(obj);
00269             return status;
00270         }
00271     }
00272     
00273     // clearing the serial interrupt here might cause an unintended rewrite of the last byte
00274     // see also issue report https://mbed.org/users/mbed_official/code/mbed/issues/1
00275     // i2c_clear_SI(obj);
00276     
00277     // If not repeated start, send stop.
00278     if (stop) {
00279         i2c_stop(obj);
00280     }
00281     
00282     return 0;
00283 }
00284 
00285 void i2c_reset(i2c_t *obj) {
00286     i2c_stop(obj);
00287 }
00288 
00289 int i2c_byte_read(i2c_t *obj, int last) {
00290     return (i2c_do_read(obj, last) & 0xFF);
00291 }
00292 
00293 int i2c_byte_write(i2c_t *obj, int data) {
00294     int ack;
00295     int status = i2c_do_write(obj, (data & 0xFF), 0);
00296     
00297     switch(status) {
00298         case 0x18: case 0x28:       // Master transmit ACKs
00299             ack = 1;
00300             break;
00301         
00302         case 0x40:                  // Master receive address transmitted ACK
00303             ack = 1;
00304             break;
00305         
00306         case 0xB8:                  // Slave transmit ACK
00307             ack = 1;
00308             break;
00309         
00310         default:
00311             ack = 0;
00312             break;
00313     }
00314     
00315     return ack;
00316 }
00317 
00318 void i2c_slave_mode(i2c_t *obj, int enable_slave) {
00319     if (enable_slave != 0) {
00320         i2c_conclr(obj, 1, 1, 1, 0);
00321         i2c_conset(obj, 0, 0, 0, 1);
00322     } else {
00323         i2c_conclr(obj, 1, 1, 1, 1);
00324     }
00325 }
00326 
00327 int i2c_slave_receive(i2c_t *obj) {
00328     int status;
00329     int retval;
00330     
00331     status = i2c_status(obj);
00332     switch(status) {
00333         case 0x60: retval = 3; break;
00334         case 0x70: retval = 2; break;
00335         case 0xA8: retval = 1; break;
00336         default  : retval = 0; break;
00337     }
00338     
00339     return(retval);
00340 }
00341 
00342 int i2c_slave_read(i2c_t *obj, char *data, int length) {
00343     int count = 0;
00344     int status;
00345     
00346     do {
00347         i2c_clear_SI(obj);
00348         i2c_wait_SI(obj);
00349         status = i2c_status(obj);
00350         if((status == 0x80) || (status == 0x90)) {
00351             data[count] = I2C_DAT(obj) & 0xFF;
00352         }
00353         count++;
00354     } while (((status == 0x80) || (status == 0x90) ||
00355             (status == 0x060) || (status == 0x70)) && (count < length));
00356     
00357     if(status != 0xA0) {
00358         i2c_stop(obj);
00359     }
00360     
00361     i2c_clear_SI(obj);
00362     
00363     return (count - 1);
00364 }
00365 
00366 int i2c_slave_write(i2c_t *obj, const char *data, int length) {
00367     int count = 0;
00368     int status;
00369     
00370     if(length <= 0) {
00371         return(0);
00372     }
00373     
00374     do {
00375         status = i2c_do_write(obj, data[count], 0);
00376         count++;
00377     } while ((count < length) && (status == 0xB8));
00378     
00379     if((status != 0xC0) && (status != 0xC8)) {
00380         i2c_stop(obj);
00381     }
00382     
00383     i2c_clear_SI(obj);
00384     
00385     return(count);
00386 }
00387 
00388 void i2c_slave_address(i2c_t *obj, int idx, uint32_t address, uint32_t mask) {
00389     uint32_t addr;
00390     
00391     if ((idx >= 0) && (idx <= 3)) {
00392         addr = ((uint32_t)obj->i2c) + I2C_addr_offset[0][idx];
00393         *((uint32_t *) addr) = address & 0xFF;
00394     }
00395 }