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 
00018 #include "cmsis.h"
00019 #include "pinmap.h"
00020 #include "error.h"
00021 
00022 #include <math.h>
00023 #include <string.h>
00024 
00025 /* Acceptance filter mode in AFMR register */
00026 #define ACCF_OFF                0x01
00027 #define ACCF_BYPASS             0x02
00028 #define ACCF_ON                 0x00
00029 #define ACCF_FULLCAN            0x04
00030 
00031 /* There are several bit timing calculators on the internet.
00032 http://www.port.de/engl/canprod/sv_req_form.html
00033 http://www.kvaser.com/can/index.htm
00034 */
00035 
00036 static const PinMap PinMap_CAN_RD[] = {
00037     {P0_0 , CAN_1, 1},
00038     {P0_4 , CAN_2, 2},
00039     {P0_21, CAN_1, 3},
00040     {P2_7 , CAN_2, 1},
00041     {NC   , NC   , 0}
00042 };
00043 
00044 static const PinMap PinMap_CAN_TD[] = {
00045     {P0_1 , CAN_1, 1},
00046     {P0_5 , CAN_2, 2},
00047     {P0_22, CAN_1, 3},
00048     {P2_8 , CAN_2, 1},
00049     {NC   , NC   , 0}
00050 };
00051 
00052 // Type definition to hold a CAN message
00053 struct CANMsg {
00054     unsigned int  reserved1 : 16;
00055     unsigned int  dlc       :  4; // Bits 16..19: DLC - Data Length Counter
00056     unsigned int  reserved0 : 10;
00057     unsigned int  rtr       :  1; // Bit 30: Set if this is a RTR message
00058     unsigned int  type      :  1; // Bit 31: Set if this is a 29-bit ID message
00059     unsigned int  id;             // CAN Message ID (11-bit or 29-bit)
00060     unsigned char data[8];        // CAN Message Data Bytes 0-7
00061 };
00062 typedef struct CANMsg CANMsg;
00063 
00064 static uint32_t can_disable(can_t *obj) {
00065     uint32_t sm = obj->dev->MOD;
00066     obj->dev->MOD |= 1;
00067     return sm;
00068 }
00069 
00070 static inline void can_enable(can_t *obj) {
00071     if (obj->dev->MOD & 1) {
00072         obj->dev->MOD &= ~(1);
00073     }
00074 }
00075 
00076 static int can_pclk(can_t *obj) {
00077     int value = 0;
00078     switch ((int)obj->dev) {
00079         case CAN_1: value = (LPC_SC->PCLKSEL0 & (0x3 << 26)) >> 26; break;
00080         case CAN_2: value = (LPC_SC->PCLKSEL0 & (0x3 << 28)) >> 28; break;
00081     }
00082 
00083     switch (value) {
00084         case 1: return 1;
00085         case 2: return 2;
00086         case 3: return 6;
00087         default: return 4;
00088     }
00089 }
00090 
00091 // This table has the sampling points as close to 75% as possible. The first
00092 // value is TSEG1, the second TSEG2.
00093 static const int timing_pts[23][2] = {
00094     {0x0, 0x0},      // 2,  50%
00095     {0x1, 0x0},      // 3,  67%
00096     {0x2, 0x0},      // 4,  75%
00097     {0x3, 0x0},      // 5,  80%
00098     {0x3, 0x1},      // 6,  67%
00099     {0x4, 0x1},      // 7,  71%
00100     {0x5, 0x1},      // 8,  75%
00101     {0x6, 0x1},      // 9,  78%
00102     {0x6, 0x2},      // 10, 70%
00103     {0x7, 0x2},      // 11, 73%
00104     {0x8, 0x2},      // 12, 75%
00105     {0x9, 0x2},      // 13, 77%
00106     {0x9, 0x3},      // 14, 71%
00107     {0xA, 0x3},      // 15, 73%
00108     {0xB, 0x3},      // 16, 75%
00109     {0xC, 0x3},      // 17, 76%
00110     {0xD, 0x3},      // 18, 78%
00111     {0xD, 0x4},      // 19, 74%
00112     {0xE, 0x4},      // 20, 75%
00113     {0xF, 0x4},      // 21, 76%
00114     {0xF, 0x5},      // 22, 73%
00115     {0xF, 0x6},      // 23, 70%
00116     {0xF, 0x7},      // 24, 67%
00117 };
00118 
00119 static unsigned int can_speed(unsigned int sclk, unsigned int pclk, unsigned int cclk, unsigned char psjw) {
00120     uint32_t    btr;
00121     uint16_t    brp = 0;
00122     uint32_t    calcbit;
00123     uint32_t    bitwidth;
00124     int         hit = 0;
00125     int         bits;
00126     
00127     bitwidth = sclk / (pclk * cclk);
00128     
00129     brp = bitwidth / 0x18;
00130     while ((!hit) && (brp < bitwidth / 4)) {
00131         brp++;
00132         for (bits = 22; bits > 0; bits--) {
00133             calcbit = (bits + 3) * (brp + 1);
00134             if (calcbit == bitwidth) {
00135                 hit = 1;
00136                 break;
00137             }
00138         }
00139     }
00140     
00141     if (hit) {
00142         btr = ((timing_pts[bits][1] << 20) & 0x00700000)
00143             | ((timing_pts[bits][0] << 16) & 0x000F0000)
00144             | ((psjw                << 14) & 0x0000C000)
00145             | ((brp                 <<  0) & 0x000003FF);
00146     } else {
00147         btr = 0xFFFFFFFF;
00148     }
00149     
00150     return btr;
00151 
00152 }
00153 
00154 void can_init(can_t *obj, PinName rd, PinName td) {
00155     CANName can_rd = (CANName)pinmap_peripheral(rd, PinMap_CAN_RD);
00156     CANName can_td = (CANName)pinmap_peripheral(td, PinMap_CAN_TD);
00157     obj->dev = (LPC_CAN_TypeDef *)pinmap_merge(can_rd, can_td);
00158     if ((int)obj->dev == NC) {
00159         error("CAN pin mapping failed");
00160     }
00161 
00162     switch ((int)obj->dev) {
00163         case CAN_1: LPC_SC->PCONP |= 1 << 13; break;
00164         case CAN_2: LPC_SC->PCONP |= 1 << 14; break;
00165     }
00166 
00167     pinmap_pinout(rd, PinMap_CAN_RD);
00168     pinmap_pinout(td, PinMap_CAN_TD);
00169 
00170     can_reset(obj);
00171     obj->dev->IER = 0;             // Disable Interrupts
00172     can_frequency(obj, 100000);
00173 
00174     LPC_CANAF->AFMR = ACCF_BYPASS; // Bypass Filter
00175 }
00176 
00177 void can_free(can_t *obj) {
00178     switch ((int)obj->dev) {
00179         case CAN_1: LPC_SC->PCONP &= ~(1 << 13); break;
00180         case CAN_2: LPC_SC->PCONP &= ~(1 << 14); break;
00181     }
00182 }
00183 
00184 int can_frequency(can_t *obj, int f) {
00185     int pclk = can_pclk(obj);
00186     
00187     int btr = can_speed(SystemCoreClock, pclk, (unsigned int)f, 1);
00188 
00189     if (btr > 0) {
00190         uint32_t modmask = can_disable(obj);
00191         obj->dev->BTR = btr;
00192         obj->dev->MOD = modmask;
00193         return 1;
00194     } else {
00195         return 0;
00196     }
00197 }
00198 
00199 int can_write(can_t *obj, CAN_Message msg, int cc) {
00200     unsigned int CANStatus;
00201     CANMsg m;
00202 
00203     can_enable(obj);
00204 
00205     m.id   = msg.id ;
00206     m.dlc  = msg.len & 0xF;
00207     m.rtr  = msg.type;
00208     m.type = msg.format;
00209     memcpy(m.data, msg.data, msg.len);
00210     const unsigned int *buf = (const unsigned int *)&m;
00211 
00212     CANStatus = obj->dev->SR;
00213     if (CANStatus & 0x00000004) {
00214         obj->dev->TFI1 = buf[0] & 0xC00F0000;
00215         obj->dev->TID1 = buf[1];
00216         obj->dev->TDA1 = buf[2];
00217         obj->dev->TDB1 = buf[3];
00218         if(cc) {
00219             obj->dev->CMR = 0x30;
00220         } else {
00221             obj->dev->CMR = 0x21;
00222         }
00223         return 1;
00224 
00225     } else if (CANStatus & 0x00000400) {
00226         obj->dev->TFI2 = buf[0] & 0xC00F0000;
00227         obj->dev->TID2 = buf[1];
00228         obj->dev->TDA2 = buf[2];
00229         obj->dev->TDB2 = buf[3];
00230         if (cc) {
00231             obj->dev->CMR = 0x50;
00232         } else {
00233             obj->dev->CMR = 0x41;
00234         }
00235         return 1;
00236 
00237     } else if (CANStatus & 0x00040000) {
00238         obj->dev->TFI3 = buf[0] & 0xC00F0000;
00239         obj->dev->TID3 = buf[1];
00240         obj->dev->TDA3 = buf[2];
00241         obj->dev->TDB3 = buf[3];
00242         if (cc) {
00243             obj->dev->CMR = 0x90;
00244         } else {
00245             obj->dev->CMR = 0x81;
00246         }
00247         return 1;
00248     }
00249 
00250     return 0;
00251 }
00252 
00253 int can_read(can_t *obj, CAN_Message *msg) {
00254     CANMsg x;
00255     unsigned int *i = (unsigned int *)&x;
00256 
00257     can_enable(obj);
00258 
00259     if (obj->dev->GSR & 0x1) {
00260         *i++ = obj->dev->RFS;  // Frame
00261         *i++ = obj->dev->RID;  // ID
00262         *i++ = obj->dev->RDA;  // Data A
00263         *i++ = obj->dev->RDB;  // Data B
00264         obj->dev->CMR = 0x04;  // release receive buffer
00265 
00266         msg->id     = x.id;
00267         msg->len    = x.dlc;
00268         msg->format = (x.type)? CANExtended : CANStandard;
00269         msg->type   = (x.rtr)?  CANRemote:    CANData;
00270         memcpy(msg->data,x.data,x.dlc);
00271         return 1;
00272     }
00273 
00274     return 0;
00275 }
00276 
00277 void can_reset(can_t *obj) {
00278     can_disable(obj);
00279     obj->dev->GSR = 0; // Reset error counter when CAN1MOD is in reset
00280 }
00281 
00282 unsigned char can_rderror(can_t *obj) {
00283     return (obj->dev->GSR >> 16) & 0xFF;
00284 }
00285 
00286 unsigned char can_tderror(can_t *obj) {
00287     return (obj->dev->GSR >> 24) & 0xFF;
00288 }
00289 
00290 void can_monitor(can_t *obj, int silent) {
00291     uint32_t mod_mask = can_disable(obj);
00292     if (silent) {
00293         obj->dev->MOD |= (1 << 1);
00294     } else {
00295         obj->dev->MOD &= ~(1 << 1);
00296     }
00297     if (!(mod_mask & 1)) {
00298         can_enable(obj);
00299     }
00300 }