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#include <stdio.h>
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#include <stdlib.h>
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/*
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CiA DS-301, p.20
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*/
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#define MAX_BIT_TIMING 9
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int table_bit_timing_settings[MAX_BIT_TIMING][3] =
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{
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{1000, 8, 6}, /* baudrate, number of time quanta per bit, tsync+tseg1 */
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{800, 10, 8},
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{500, 16, 14},
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{250, 16, 14},
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{125, 16, 14},
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{100, 16, 14},
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{ 50, 16, 14},
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{ 25, 16, 14},
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{ 10, 16, 14}
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};
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void can_timing_registers(double f, int *v)
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/* fill the vector v with the proper setting for TIMER 0 and TIMER 1
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regarding the clock and the baudrate */
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{
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int i;
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int BRP, TSEG1, TSEG2;
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double nominal, tq, tscl;
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double tclk = 1 / (f*1e6); /* sec */
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for(i=0; i<MAX_BIT_TIMING; i++)
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{
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nominal = 1. / (table_bit_timing_settings[i][0]*1e3); /* nominal bit time */
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tq = nominal / table_bit_timing_settings[i][1]; /* time quanta */
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tscl = tq; /* Tsyncseg = Tscl (ref. SJA 1000 datasheet, p.51) */
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/* tcsl = 2 tclk (BRP + 1) */
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BRP = (int)(tscl / (2. * tclk) - 1.);
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/*
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BRT0 = SJW * 64 + BRP
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SJW : synchonisation jump Width, user defined (0..3)
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*/
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/* tseg1 = tscl * (TSEG1 + 1) */
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TSEG1 = (int)((table_bit_timing_settings[i][2] - 1)*tq/tscl - 1.);
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/* tseg2 = tscl * (TSEG2 + 1) */
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TSEG2 = (int)(2.*tq/tscl - 1.);
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/*
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BRT1 = SAM*128 + TSEG2*16 + TSEG1
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SAM = Sampling (0 = single sampling, 1 = triple sampling)
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*/
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if (BRP < 64)
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{
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v[2*i] = BRP;
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v[2*i+1] = TSEG1+16*TSEG2;
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}
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else
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{
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v[2*i] = 0;
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v[2*i+1] = 0;
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}
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}
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}
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void print_header(double frequency, /* clock rate in MHz*/
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int sjw) /* 0..3 */
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{
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int i, array[18];
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FILE *f = fopen("baudrate_table.h", "w");
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can_timing_registers(frequency, array);
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fprintf(f, "#if !defined(_BAUDRATE_TABLE_H_)\n");
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fprintf(f, "#define _BAUDRATE_TABLE_H_\n");
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fprintf(f, "\n");
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fprintf(f, "/*\n");
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fprintf(f, "this file must be include only once in the project\n");
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fprintf(f, "*/\n");
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fprintf(f, "\n");
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fprintf(f, "/* clock speed in MHz */\n");
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fprintf(f, "#define CAN_CONTROLER_CLOCK_SPEED %.3lf\n", frequency);
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fprintf(f, "#define CAN_CONTROLER_PHASE_SHIFT_TOLERANCE %d\n", sjw);
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sjw = sjw << 6;
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fprintf(f, "\n");
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fprintf(f, "static int can_baudrate_registers[9][3] =\n");
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fprintf(f, "{ /* BTR0 BTR1 */\n");
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for(i=0; i<MAX_BIT_TIMING; i++)
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{
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if (array[2*i] == 0 && array[2*i+1] == 0)
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fprintf(f, " {0, 0x00, 0x00}, /* %4d kbits/s -- out of range*/\n",
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table_bit_timing_settings[i][0]);
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else
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fprintf(f, " {1, 0x%02x, 0x%02x}, /* %4d kbits/s */\n",
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sjw|array[2*i], array[2*i+1],
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table_bit_timing_settings[i][0]);
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}
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fprintf(f, "};\n");
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fprintf(f, "\n");
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fprintf(f, "#endif\n\n");
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fclose(f);
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}
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int main(int argc, char *argv[])
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{
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if (argc == 3)
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print_header(atof(argv[1]), atoi(argv[2]));
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else
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printf("usage: %s clock_in_Mhz error_rate_in_percent\n", argv[0]);
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}
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