123 lines
3.3 KiB
C
123 lines
3.3 KiB
C
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#include <stdint.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include "soft_uart.h"
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static inline uint32_t samples_per_etu(struct suart_data *su)
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{
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return su->samplerate / su->recip_etu;
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}
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static const char *state_strings[] = {
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[WAIT_RESET] = "WAIT_RESET",
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[IN_RESET] = "IN_RESET",
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[WAIT_START_FALLEDGE] = "WAIT_START_FALLEDGE",
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[WAIT_START_ETU07] = "WAIT_START_ETU07",
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[RX_BITS] = "RX_BITS",
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[POST_RX_WAIT_HIGH] = "POST_RX_WAIT_HIGH",
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};
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static void change_state(struct suart_data *su, enum suart_state new_state)
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{
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printf("State change: %s -> %s\n", state_strings[su->state], state_strings[new_state]);
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su->state = new_state;
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}
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/* According to ISO/IEC 7816-3 Section 6.1.2 */
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int suart_process_sample_bit(struct suart_data *suart, uint8_t clk_bit, uint8_t rst_bit, uint8_t sample_bit)
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{
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uint32_t samp_per_etu = samples_per_etu(suart);
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uint8_t next_bit;
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if (rst_bit == 0 && suart->state != IN_RESET) {
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change_state(suart, IN_RESET);
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/* FIXME: reset some other things? */
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}
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switch (suart->state) {
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case WAIT_RESET:
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if (rst_bit == 0)
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change_state(suart, IN_RESET);
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break;
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case IN_RESET:
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if (rst_bit == 1)
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change_state(suart, WAIT_START_FALLEDGE);
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break;
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case WAIT_START_FALLEDGE:
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if (sample_bit == 0) {
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suart->sample_after_sbit = 0;
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suart->bits_pending = suart->num_bits + 1;
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change_state(suart, WAIT_START_ETU07);
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}
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break;
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case WAIT_START_ETU07:
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if (suart->sample_after_sbit > (samp_per_etu/2)+1) {
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if (sample_bit != 0) {
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printf("!!!!!!!!!!!!!!!!!!!!! start bit after 0.7 * ETU no longer low\n");
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} else {
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change_state(suart, RX_BITS);
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suart->rx_char = 0;
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}
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}
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/* else stay in this state until the condition is true */
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break;
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case RX_BITS:
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next_bit = suart->num_bits+1 - suart->bits_pending;
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#if 0
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printf("\tRX_BITS: IO = %u, next_bit = %u, sample_after_sbit = %u, samp_per_etu = %u, required_after_sbit = %u\n",
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sample_bit, next_bit, suart->sample_after_sbit, samp_per_etu,
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(samp_per_etu/2) + ((next_bit+1) * samp_per_etu));
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#endif
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if (suart->sample_after_sbit > (samp_per_etu/2) + ((next_bit+1) * samp_per_etu)) {
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/* check if this is the parity bit */
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//printf("new_bit = %u\n", sample_bit);
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if (next_bit == suart->num_bits) {
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/* FIXME calculate parity */
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} else {
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/* an actual data bit */
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/* Section 6.1.4.1 */
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if (suart->convention == INVERSE_CONVENTION) {
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if (sample_bit == 1)
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sample_bit = 0x00;
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else
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sample_bit = 0x80;
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/* shift existing patter one to the right */
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suart->rx_char = suart->rx_char >> 1;
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/* mask in the additional bit */
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suart->rx_char |= sample_bit;
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} else {
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suart->rx_char |= (sample_bit << next_bit);
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}
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}
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suart->bits_pending--;
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}
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if (suart->bits_pending == 0) {
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/* output the character that we decoded */
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printf("Output Byte: %02x\n", suart->rx_char);
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change_state(suart, POST_RX_WAIT_HIGH);
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}
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break;
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case POST_RX_WAIT_HIGH:
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if (sample_bit == 0x01) {
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/* return to initial state */
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change_state(suart, WAIT_START_FALLEDGE);
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}
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break;
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}
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suart->sample_after_sbit++;
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}
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void suart_init(struct suart_data *su)
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{
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su->state = WAIT_RESET;
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su->convention = DIRECT_CONVENTION;
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printf("Samplerate = %u\n", su->samplerate);
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printf("etu = 1 / %u\n", su->recip_etu);
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printf("samp_per_etu = %u\n", samples_per_etu(su));
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}
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