can_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 "can_api.h"
00017 #include "cmsis.h"
00018 #include "pinmap.h"
00019 #include "error.h"
00020 
00021 #include <math.h>
00022 #include <string.h>
00023 
00024 /* Acceptance filter mode in AFMR register */
00025 #define ACCF_OFF                0x01
00026 #define ACCF_BYPASS             0x02
00027 #define ACCF_ON                 0x00
00028 #define ACCF_FULLCAN            0x04
00029 
00030 /* There are several bit timing calculators on the internet.
00031 http://www.port.de/engl/canprod/sv_req_form.html
00032 http://www.kvaser.com/can/index.htm
00033 */
00034 
00035 static const PinMap PinMap_CAN_RD[] = {
00036     {P0_0 , CAN_1, 1},
00037     {P0_4 , CAN_2, 2},
00038     {P0_21, CAN_1, 3},
00039     {P2_7 , CAN_2, 1},
00040     {NC   , NC   , 0}
00041 };
00042 
00043 static const PinMap PinMap_CAN_TD[] = {
00044     {P0_1 , CAN_1, 1},
00045     {P0_5 , CAN_2, 2},
00046     {P0_22, CAN_1, 3},
00047     {P2_8 , CAN_2, 1},
00048     {NC   , NC   , 0}
00049 };
00050 
00051 // Type definition to hold a CAN message
00052 struct CANMsg {
00053     unsigned int  reserved1 : 16;
00054     unsigned int  dlc       :  4; // Bits 16..19: DLC - Data Length Counter
00055     unsigned int  reserved0 : 10;
00056     unsigned int  rtr       :  1; // Bit 30: Set if this is a RTR message
00057     unsigned int  type      :  1; // Bit 31: Set if this is a 29-bit ID message
00058     unsigned int  id;             // CAN Message ID (11-bit or 29-bit)
00059     unsigned char data[8];        // CAN Message Data Bytes 0-7
00060 };
00061 typedef struct CANMsg CANMsg;
00062 
00063 static uint32_t can_disable(can_t *obj) {
00064     uint32_t sm = obj->dev->MOD;
00065     obj->dev->MOD |= 1;
00066     return sm;
00067 }
00068 
00069 static inline void can_enable(can_t *obj) {
00070     if (obj->dev->MOD & 1) {
00071         obj->dev->MOD &= ~(1);
00072     }
00073 }
00074 
00075 static int can_pclk(can_t *obj) {
00076     int value = 0;
00077     switch ((int)obj->dev) {
00078         case CAN_1: value = (LPC_SC->PCLKSEL0 & (0x3 << 26)) >> 26; break;
00079         case CAN_2: value = (LPC_SC->PCLKSEL0 & (0x3 << 28)) >> 28; break;
00080     }
00081     
00082     switch (value) {
00083         case 1: return 1;
00084         case 2: return 2;
00085         case 3: return 6;
00086         default: return 4;
00087     }
00088 }
00089 
00090 // This table has the sampling points as close to 75% as possible. The first
00091 // value is TSEG1, the second TSEG2.
00092 static const int timing_pts[23][2] = {
00093     {0x0, 0x0},      // 2,  50%
00094     {0x1, 0x0},      // 3,  67%
00095     {0x2, 0x0},      // 4,  75%
00096     {0x3, 0x0},      // 5,  80%
00097     {0x3, 0x1},      // 6,  67%
00098     {0x4, 0x1},      // 7,  71%
00099     {0x5, 0x1},      // 8,  75%
00100     {0x6, 0x1},      // 9,  78%
00101     {0x6, 0x2},      // 10, 70%
00102     {0x7, 0x2},      // 11, 73%
00103     {0x8, 0x2},      // 12, 75%
00104     {0x9, 0x2},      // 13, 77%
00105     {0x9, 0x3},      // 14, 71%
00106     {0xA, 0x3},      // 15, 73%
00107     {0xB, 0x3},      // 16, 75%
00108     {0xC, 0x3},      // 17, 76%
00109     {0xD, 0x3},      // 18, 78%
00110     {0xD, 0x4},      // 19, 74%
00111     {0xE, 0x4},      // 20, 75%
00112     {0xF, 0x4},      // 21, 76%
00113     {0xF, 0x5},      // 22, 73%
00114     {0xF, 0x6},      // 23, 70%
00115     {0xF, 0x7},      // 24, 67%
00116 };
00117 
00118 static unsigned int can_speed(unsigned int sclk, unsigned int pclk, unsigned int cclk, unsigned char psjw) {
00119     uint32_t    btr;
00120     uint16_t    brp = 0;
00121     uint32_t    calcbit;
00122     uint32_t    bitwidth;
00123     int         hit = 0;
00124     int         bits;
00125     
00126     bitwidth = sclk / (pclk * cclk);
00127     
00128     brp = bitwidth / 0x18;
00129     while ((!hit) && (brp < bitwidth / 4)) {
00130         brp++;
00131         for (bits = 22; bits > 0; bits--) {
00132             calcbit = (bits + 3) * (brp + 1);
00133             if (calcbit == bitwidth) {
00134                 hit = 1;
00135                 break;
00136             }
00137         }
00138     }
00139     
00140     if (hit) {
00141         btr = ((timing_pts[bits][1] << 20) & 0x00700000)
00142             | ((timing_pts[bits][0] << 16) & 0x000F0000)
00143             | ((psjw                << 14) & 0x0000C000)
00144             | ((brp                 <<  0) & 0x000003FF);
00145     } else {
00146         btr = 0xFFFFFFFF;
00147     }
00148     
00149     return btr;
00150 }
00151 
00152 void can_init(can_t *obj, PinName rd, PinName td) {
00153     CANName can_rd = (CANName)pinmap_peripheral(rd, PinMap_CAN_RD);
00154     CANName can_td = (CANName)pinmap_peripheral(td, PinMap_CAN_TD);
00155     obj->dev = (LPC_CAN_TypeDef *)pinmap_merge(can_rd, can_td);
00156     if ((int)obj->dev == NC) {
00157         error("CAN pin mapping failed");
00158     }
00159     
00160     switch ((int)obj->dev) {
00161         case CAN_1: LPC_SC->PCONP |= 1 << 13; break;
00162         case CAN_2: LPC_SC->PCONP |= 1 << 14; break;
00163     }
00164     
00165     pinmap_pinout(rd, PinMap_CAN_RD);
00166     pinmap_pinout(td, PinMap_CAN_TD);
00167     
00168     can_reset(obj);
00169     obj->dev->IER = 0;             // Disable Interrupts
00170     can_frequency(obj, 100000);
00171     
00172     LPC_CANAF->AFMR = ACCF_BYPASS; // Bypass Filter
00173 }
00174 
00175 void can_free(can_t *obj) {
00176     switch ((int)obj->dev) {
00177         case CAN_1: LPC_SC->PCONP &= ~(1 << 13); break;
00178         case CAN_2: LPC_SC->PCONP &= ~(1 << 14); break;
00179     }
00180 }
00181 
00182 int can_frequency(can_t *obj, int f) {
00183     int pclk = can_pclk(obj);
00184     int btr = can_speed(SystemCoreClock, pclk, (unsigned int)f, 1);
00185     
00186     if (btr > 0) {
00187         uint32_t modmask = can_disable(obj);
00188         obj->dev->BTR = btr;
00189         obj->dev->MOD = modmask;
00190         return 1;
00191     } else {
00192         return 0;
00193     }
00194 }
00195 
00196 int can_write(can_t *obj, CAN_Message msg, int cc) {
00197     unsigned int CANStatus;
00198     CANMsg m;
00199     
00200     can_enable(obj);
00201     
00202     m.id   = msg.id ;
00203     m.dlc  = msg.len & 0xF;
00204     m.rtr  = msg.type;
00205     m.type = msg.format;
00206     memcpy(m.data, msg.data, msg.len);
00207     const unsigned int *buf = (const unsigned int *)&m;
00208     
00209     CANStatus = obj->dev->SR;
00210     if (CANStatus & 0x00000004) {
00211         obj->dev->TFI1 = buf[0] & 0xC00F0000;
00212         obj->dev->TID1 = buf[1];
00213         obj->dev->TDA1 = buf[2];
00214         obj->dev->TDB1 = buf[3];
00215         if (cc) {
00216             obj->dev->CMR = 0x30;
00217         } else {
00218             obj->dev->CMR = 0x21;
00219         }
00220         return 1;
00221     
00222     } else if (CANStatus & 0x00000400) {
00223         obj->dev->TFI2 = buf[0] & 0xC00F0000;
00224         obj->dev->TID2 = buf[1];
00225         obj->dev->TDA2 = buf[2];
00226         obj->dev->TDB2 = buf[3];
00227         if (cc) {
00228             obj->dev->CMR = 0x50;
00229         } else {
00230             obj->dev->CMR = 0x41;
00231         }
00232         return 1;
00233     
00234     } else if (CANStatus & 0x00040000) {
00235         obj->dev->TFI3 = buf[0] & 0xC00F0000;
00236         obj->dev->TID3 = buf[1];
00237         obj->dev->TDA3 = buf[2];
00238         obj->dev->TDB3 = buf[3];
00239         if (cc) {
00240             obj->dev->CMR = 0x90;
00241         } else {
00242             obj->dev->CMR = 0x81;
00243         }
00244         return 1;
00245     }
00246     
00247     return 0;
00248 }
00249 
00250 int can_read(can_t *obj, CAN_Message *msg) {
00251     CANMsg x;
00252     unsigned int *i = (unsigned int *)&x;
00253     
00254     can_enable(obj);
00255     
00256     if (obj->dev->GSR & 0x1) {
00257         *i++ = obj->dev->RFS;  // Frame
00258         *i++ = obj->dev->RID;  // ID
00259         *i++ = obj->dev->RDA;  // Data A
00260         *i++ = obj->dev->RDB;  // Data B
00261         obj->dev->CMR = 0x04;  // release receive buffer
00262         
00263         msg->id     = x.id;
00264         msg->len    = x.dlc;
00265         msg->format = (x.type)? CANExtended : CANStandard;
00266         msg->type   = (x.rtr)?  CANRemote:    CANData;
00267         memcpy(msg->data,x.data,x.dlc);
00268         return 1;
00269     }
00270     
00271     return 0;
00272 }
00273 
00274 void can_reset(can_t *obj) {
00275     can_disable(obj);
00276     obj->dev->GSR = 0; // Reset error counter when CAN1MOD is in reset
00277 }
00278 
00279 unsigned char can_rderror(can_t *obj) {
00280     return (obj->dev->GSR >> 16) & 0xFF;
00281 }
00282 
00283 unsigned char can_tderror(can_t *obj) {
00284     return (obj->dev->GSR >> 24) & 0xFF;
00285 }
00286 
00287 void can_monitor(can_t *obj, int silent) {
00288     uint32_t mod_mask = can_disable(obj);
00289     if (silent) {
00290         obj->dev->MOD |= (1 << 1);
00291     } else {
00292         obj->dev->MOD &= ~(1 << 1);
00293     }
00294     if (!(mod_mask & 1)) {
00295         can_enable(obj);
00296     }
00297 }