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286 lines
7.7 KiB
286 lines
7.7 KiB
#define GMLAN_TICKS_PER_SECOND 33300 //1sec @ 33.3kbps
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#define GMLAN_TICKS_PER_TIMEOUT_TICKLE 500 //15ms @ 33.3kbps
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#define GMLAN_HIGH 0 //0 is high on bus (dominant)
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#define GMLAN_LOW 1 //1 is low on bus
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#define DISABLED -1
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#define BITBANG 0
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#define GPIO_SWITCH 1
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#define MAX_BITS_CAN_PACKET (200)
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int gmlan_alt_mode = DISABLED;
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// returns out_len
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int do_bitstuff(char *out, char *in, int in_len) {
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int last_bit = -1;
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int bit_cnt = 0;
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int j = 0;
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for (int i = 0; i < in_len; i++) {
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char bit = in[i];
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out[j] = bit;
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j++;
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// do the stuffing
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if (bit == last_bit) {
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bit_cnt++;
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if (bit_cnt == 5) {
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// 5 in a row the same, do stuff
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last_bit = !bit;
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out[j] = last_bit;
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j++;
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bit_cnt = 1;
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}
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} else {
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// this is a new bit
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last_bit = bit;
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bit_cnt = 1;
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}
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}
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return j;
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}
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int append_crc(char *in, int in_len) {
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unsigned int crc = 0;
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for (int i = 0; i < in_len; i++) {
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crc <<= 1;
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if (((unsigned int)(in[i]) ^ ((crc >> 15) & 1U)) != 0U) {
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crc = crc ^ 0x4599U;
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}
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crc &= 0x7fffU;
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}
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int in_len_copy = in_len;
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for (int i = 14; i >= 0; i--) {
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in[in_len_copy] = (crc >> (unsigned int)(i)) & 1U;
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in_len_copy++;
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}
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return in_len_copy;
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}
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int append_bits(char *in, int in_len, char *app, int app_len) {
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int in_len_copy = in_len;
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for (int i = 0; i < app_len; i++) {
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in[in_len_copy] = app[i];
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in_len_copy++;
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}
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return in_len_copy;
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}
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int append_int(char *in, int in_len, int val, int val_len) {
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int in_len_copy = in_len;
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for (int i = val_len - 1; i >= 0; i--) {
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in[in_len_copy] = ((unsigned int)(val) & (1U << (unsigned int)(i))) != 0U;
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in_len_copy++;
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}
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return in_len_copy;
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}
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int get_bit_message(char *out, CAN_FIFOMailBox_TypeDef *to_bang) {
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char pkt[MAX_BITS_CAN_PACKET];
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char footer[] = {
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1, // CRC delimiter
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1, // ACK
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1, // ACK delimiter
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1,1,1,1,1,1,1, // EOF
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1,1,1, // IFS
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};
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int len = 0;
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// test packet
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int dlc_len = to_bang->RDTR & 0xF;
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len = append_int(pkt, len, 0, 1); // Start-of-frame
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if ((to_bang->RIR & 4) != 0) {
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// extended identifier
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len = append_int(pkt, len, to_bang->RIR >> 21, 11); // Identifier
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len = append_int(pkt, len, 3, 2); // SRR+IDE
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len = append_int(pkt, len, (to_bang->RIR >> 3) & ((1U << 18) - 1U), 18); // Identifier
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len = append_int(pkt, len, 0, 3); // RTR+r1+r0
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} else {
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// standard identifier
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len = append_int(pkt, len, to_bang->RIR >> 21, 11); // Identifier
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len = append_int(pkt, len, 0, 3); // RTR+IDE+reserved
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}
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len = append_int(pkt, len, dlc_len, 4); // Data length code
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// append data
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for (int i = 0; i < dlc_len; i++) {
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unsigned char dat = ((unsigned char *)(&(to_bang->RDLR)))[i];
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len = append_int(pkt, len, dat, 8);
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}
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// append crc
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len = append_crc(pkt, len);
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// do bitstuffing
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len = do_bitstuff(out, pkt, len);
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// append footer
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len = append_bits(out, len, footer, sizeof(footer));
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return len;
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}
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void setup_timer4(void) {
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// setup
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TIM4->PSC = 48-1; // tick on 1 us
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TIM4->CR1 = TIM_CR1_CEN; // enable
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TIM4->ARR = 30-1; // 33.3 kbps
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// in case it's disabled
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NVIC_EnableIRQ(TIM4_IRQn);
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// run the interrupt
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TIM4->DIER = TIM_DIER_UIE; // update interrupt
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TIM4->SR = 0;
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}
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int gmlan_timeout_counter = GMLAN_TICKS_PER_TIMEOUT_TICKLE; //GMLAN transceiver times out every 17ms held high; tickle every 15ms
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int can_timeout_counter = GMLAN_TICKS_PER_SECOND; //1 second
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int inverted_bit_to_send = GMLAN_HIGH;
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int gmlan_switch_below_timeout = -1;
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int gmlan_switch_timeout_enable = 0;
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void gmlan_switch_init(int timeout_enable) {
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gmlan_switch_timeout_enable = timeout_enable;
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gmlan_alt_mode = GPIO_SWITCH;
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gmlan_switch_below_timeout = 1;
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set_gpio_mode(GPIOB, 13, MODE_OUTPUT);
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setup_timer4();
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inverted_bit_to_send = GMLAN_LOW; //We got initialized, set the output low
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}
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void set_gmlan_digital_output(int to_set) {
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inverted_bit_to_send = to_set;
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/*
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puts("Writing ");
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puth(inverted_bit_to_send);
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puts("\n");
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*/
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}
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void reset_gmlan_switch_timeout(void) {
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can_timeout_counter = GMLAN_TICKS_PER_SECOND;
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gmlan_switch_below_timeout = 1;
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gmlan_alt_mode = GPIO_SWITCH;
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}
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void set_bitbanged_gmlan(int val) {
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if (val != 0) {
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GPIOB->ODR |= (1U << 13);
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} else {
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GPIOB->ODR &= ~(1U << 13);
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}
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}
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char pkt_stuffed[MAX_BITS_CAN_PACKET];
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int gmlan_sending = -1;
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int gmlan_sendmax = -1;
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bool gmlan_send_ok = true;
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int gmlan_silent_count = 0;
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int gmlan_fail_count = 0;
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#define REQUIRED_SILENT_TIME 10
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#define MAX_FAIL_COUNT 10
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void TIM4_IRQHandler(void) {
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if (gmlan_alt_mode == BITBANG) {
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if ((TIM4->SR & TIM_SR_UIF) && (gmlan_sendmax != -1)) {
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int read = get_gpio_input(GPIOB, 12);
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if (gmlan_silent_count < REQUIRED_SILENT_TIME) {
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if (read == 0) {
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gmlan_silent_count = 0;
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} else {
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gmlan_silent_count++;
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}
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} else {
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bool retry = 0;
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// in send loop
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if ((gmlan_sending > 0) && // not first bit
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((read == 0) && (pkt_stuffed[gmlan_sending-1] == 1)) && // bus wrongly dominant
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(gmlan_sending != (gmlan_sendmax - 11))) { //not ack bit
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puts("GMLAN ERR: bus driven at ");
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puth(gmlan_sending);
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puts("\n");
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retry = 1;
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} else if ((read == 1) && (gmlan_sending == (gmlan_sendmax - 11))) { // recessive during ACK
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puts("GMLAN ERR: didn't recv ACK\n");
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retry = 1;
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} else {
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// do not retry
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}
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if (retry) {
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// reset sender (retry after 7 silent)
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set_bitbanged_gmlan(1); // recessive
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gmlan_silent_count = 0;
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gmlan_sending = 0;
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gmlan_fail_count++;
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if (gmlan_fail_count == MAX_FAIL_COUNT) {
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puts("GMLAN ERR: giving up send\n");
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gmlan_send_ok = false;
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}
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} else {
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set_bitbanged_gmlan(pkt_stuffed[gmlan_sending]);
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gmlan_sending++;
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}
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}
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if ((gmlan_sending == gmlan_sendmax) || (gmlan_fail_count == MAX_FAIL_COUNT)) {
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set_bitbanged_gmlan(1); // recessive
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set_gpio_mode(GPIOB, 13, MODE_INPUT);
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TIM4->DIER = 0; // no update interrupt
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TIM4->CR1 = 0; // disable timer
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gmlan_sendmax = -1; // exit
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}
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}
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TIM4->SR = 0;
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} else if (gmlan_alt_mode == GPIO_SWITCH) {
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if ((TIM4->SR & TIM_SR_UIF) && (gmlan_switch_below_timeout != -1)) {
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if ((can_timeout_counter == 0) && gmlan_switch_timeout_enable) {
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//it has been more than 1 second since timeout was reset; disable timer and restore the GMLAN output
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set_gpio_output(GPIOB, 13, GMLAN_LOW);
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gmlan_switch_below_timeout = -1;
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gmlan_timeout_counter = GMLAN_TICKS_PER_TIMEOUT_TICKLE;
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gmlan_alt_mode = DISABLED;
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}
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else {
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can_timeout_counter--;
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if (gmlan_timeout_counter == 0) {
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//Send a 1 (bus low) every 15ms to reset the GMLAN transceivers timeout
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gmlan_timeout_counter = GMLAN_TICKS_PER_TIMEOUT_TICKLE;
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set_gpio_output(GPIOB, 13, GMLAN_LOW);
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}
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else {
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set_gpio_output(GPIOB, 13, inverted_bit_to_send);
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gmlan_timeout_counter--;
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}
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}
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}
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TIM4->SR = 0;
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} else {
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puts("invalid gmlan_alt_mode\n");
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}
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}
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bool bitbang_gmlan(CAN_FIFOMailBox_TypeDef *to_bang) {
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gmlan_send_ok = true;
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gmlan_alt_mode = BITBANG;
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if (gmlan_sendmax == -1) {
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int len = get_bit_message(pkt_stuffed, to_bang);
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gmlan_fail_count = 0;
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gmlan_silent_count = 0;
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gmlan_sending = 0;
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gmlan_sendmax = len;
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// setup for bitbang loop
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set_bitbanged_gmlan(1); // recessive
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set_gpio_mode(GPIOB, 13, MODE_OUTPUT);
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setup_timer4();
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}
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return gmlan_send_ok;
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}
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