/************************************************************************* ** The code is modified and reworked to remove all "GOTO's" and ** deprecated macros to be compatible with the latest version of WinAVR. **************************************************************************/ #include #include "j1850.h" /* **--------------------------------------------------------------------------- ** ** Abstract: Init J1850 bus driver ** ** Parameters: none ** ** Returns: none ** **--------------------------------------------------------------------------- */ void j1850_init(void) { j1850_passive(); // set VPW pin in passive state J1850_DIR_OUT |= _BV(J1850_PIN_OUT); // make VPW output pin an output J1850_PULLUP_IN |= _BV(J1850_PIN_IN); // enable pull-up on VPW pin J1850_DIR_IN &=~ _BV(J1850_PIN_IN); // make VPW input pin an input } /* **--------------------------------------------------------------------------- ** ** Abstract: Wait for J1850 bus idle ** ** Parameters: none ** ** Returns: none ** **--------------------------------------------------------------------------- */ static void j1850_wait_idle(void) { timer1_start(); while(TCNT1 < RX_IFS_MIN) // wait for minimum IFS symbol { if(is_j1850_active()) timer1_start(); // restart timer1 when bus not idle } } /* **--------------------------------------------------------------------------- ** ** Abstract: Receive J1850 frame (max 12 bytes) ** ** Parameters: Pointer to frame buffer ** ** Returns: Number of received bytes OR in case of error, error code with ** bit 7 set as error indication ** **--------------------------------------------------------------------------- */ uint8_t j1850_recv_msg(uint8_t *msg_buf ) { uint8_t nbits; // bit position counter within a byte uint8_t nbytes; // number of received bytes uint8_t bit_state;// used to compare bit state, active or passive /* wait for responds */ timer1_start(); while(!is_j1850_active()) // run as long bus is passive (IDLE) { if(TCNT1 >= WAIT_100us) // check for 100us { timer1_stop(); return J1850_RETURN_CODE_NO_DATA | 0x80; // error, no responds within 100us } } // wait for SOF timer1_start(); // restart timer1 while(is_j1850_active()) // run as long bus is active (SOF is an active symbol) { if(TCNT1 >= RX_SOF_MAX) return J1850_RETURN_CODE_BUS_ERROR | 0x80; // error on SOF timeout } timer1_stop(); if(TCNT1 < RX_SOF_MIN) return J1850_RETURN_CODE_BUS_ERROR | 0x80; // error, symbole was not SOF bit_state = is_j1850_active(); // store actual bus state timer1_start(); for(nbytes = 0; nbytes < 12; ++nbytes) { nbits = 8; do { *msg_buf <<= 1; while(is_j1850_active() == bit_state) // compare last with actual bus state, wait for change { if(TCNT1 >= RX_EOD_MIN ) // check for EOD symbol { timer1_stop(); return nbytes; // return number of received bytes } } bit_state = is_j1850_active(); // store actual bus state uint16_t tcnt1_buf = TCNT1; timer1_start(); if( tcnt1_buf < RX_SHORT_MIN) return J1850_RETURN_CODE_BUS_ERROR | 0x80; // error, pulse was to short // check for short active pulse = "1" bit if( (tcnt1_buf < RX_SHORT_MAX) && !is_j1850_active() ) *msg_buf |= 1; // check for long passive pulse = "1" bit if( (tcnt1_buf > RX_LONG_MIN) && (tcnt1_buf < RX_LONG_MAX) && is_j1850_active() ) *msg_buf |= 1; } while(--nbits);// end 8 bit while loop ++msg_buf; // store next byte } // end 12 byte for loop // return after a maximum of 12 bytes timer1_stop(); return nbytes; } /* **--------------------------------------------------------------------------- ** ** Abstract: Send J1850 frame (maximum 12 bytes) ** ** Parameters: Pointer to frame buffer, frame length ** ** Returns: 0 = error ** 1 = OK ** **--------------------------------------------------------------------------- */ uint8_t j1850_send_msg(uint8_t *msg_buf, int8_t nbytes) { if(nbytes > 12) return J1850_RETURN_CODE_DATA_ERROR; // error, message to long, see SAE J1850 j1850_wait_idle(); // wait for idle bus timer1_start(); j1850_active(); // set bus active while(TCNT1 < TX_SOF); // transmit SOF symbol uint8_t temp_byte, // temporary byte store nbits; // bit position counter within a byte uint16_t delay; // bit delay time do { temp_byte = *msg_buf; // store byte temporary nbits = 8; while (nbits--) // send 8 bits { if(nbits & 1) // start allways with passive symbol { j1850_passive(); // set bus passive timer1_start(); delay = (temp_byte & 0x80) ? TX_LONG : TX_SHORT; // send correct pulse lenght while (TCNT1 <= delay) // wait { if(!J1850_PORT_IN & _BV(J1850_PIN_IN)) // check for bus error { timer1_stop(); return J1850_RETURN_CODE_BUS_ERROR; // error, bus collision! } } } else // send active symbol { j1850_active(); // set bus active timer1_start(); delay = (temp_byte & 0x80) ? TX_SHORT : TX_LONG; // send correct pulse lenght while (TCNT1 <= delay); // wait // no error check needed, ACTIVE dominates } temp_byte <<= 1; // next bit }// end nbits while loop ++msg_buf; // next byte from buffer } while(--nbytes);// end nbytes do loop j1850_passive(); // send EOF symbol timer1_start(); while (TCNT1 <= TX_EOF); // wait for EOF complete timer1_stop(); return J1850_RETURN_CODE_OK; // no error } /* **--------------------------------------------------------------------------- ** ** Abstract: Calculate J1850 CRC ** ** Parameters: Pointer to frame buffer, frame length ** ** Returns: CRC of frame ** **--------------------------------------------------------------------------- */ // calculate J1850 message CRC uint8_t j1850_crc(uint8_t *msg_buf, int8_t nbytes) { uint8_t crc_reg=0xff,poly,byte_count,bit_count; uint8_t *byte_point; uint8_t bit_point; for (byte_count=0, byte_point=msg_buf; byte_count>=1) { if (bit_point & *byte_point) // case for new bit = 1 { if (crc_reg & 0x80) poly=1; // define the polynomial else poly=0x1c; crc_reg= ( (crc_reg << 1) | 1) ^ poly; } else // case for new bit = 0 { poly=0; if (crc_reg & 0x80) poly=0x1d; crc_reg= (crc_reg << 1) ^ poly; } } } return ~crc_reg; // Return CRC }