128 lines
3.0 KiB
C
128 lines
3.0 KiB
C
#include "paracomm.h"
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#include <stdlib.h>
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#define kMosiIdleByte 0x00
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#define kMosiStartByte 0x42
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#define kMisoIdleNibble 0x0
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#define kMisoStartNibble 0xa
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static uint8_t mosi_workbuf[2][256];
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static uint8_t mosi_workbuf_idx;
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static uint8_t mosi_workbuf_size;
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static uint8_t* mosi_sendbuf;
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static uint8_t mosi_size;
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static uint8_t mosi_sent;
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static uint8_t mosi_state;
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static uint8_t miso_recvbuf[256];
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static uint8_t miso_size;
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static uint8_t miso_received_nibbles;
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static uint8_t miso_state;
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static void (*miso_cb)(const uint8_t*, uint8_t);
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static void swapbuffers() {
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mosi_sendbuf = mosi_workbuf[mosi_workbuf_idx];
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mosi_size = mosi_workbuf_size;
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mosi_workbuf_size = 0;
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mosi_workbuf_idx = (mosi_workbuf_idx + 1) % 2;
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}
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uint8_t paracomm_nextbyte() {
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switch (mosi_state) {
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case 0:
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if (mosi_size == 0) {
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swapbuffers();
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if (mosi_size == 0) {
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return kMosiIdleByte;
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}
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}
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mosi_state = 1;
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return kMosiStartByte;
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case 1:
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// assert(mosi_size > 0)
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mosi_sent = 0;
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mosi_state = 2;
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return mosi_size;
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case 2:
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{
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uint8_t b = mosi_sendbuf[mosi_sent];
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mosi_sent += 1;
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if (mosi_sent == mosi_size) {
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swapbuffers();
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mosi_state = 0;
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}
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return b;
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}
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}
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__builtin_unreachable();
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}
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void paracomm_feed(uint8_t n) {
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switch (miso_state) {
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case 0:
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if (n == kMisoStartNibble) {
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miso_state = 1;
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} else if (n == kMisoIdleNibble) {
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} else {
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// error: spurious nibble
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}
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break;
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case 1:
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miso_size = n;
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miso_state = 2;
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break;
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case 2:
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miso_size += n << 4;
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miso_received_nibbles = 0;
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miso_state = 3;
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break;
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case 3:
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{
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uint8_t idx = miso_received_nibbles / 2;
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if (miso_received_nibbles % 2 == 0) {
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miso_recvbuf[idx] = n;
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} else {
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miso_recvbuf[idx] += n << 4;
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}
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miso_received_nibbles += 1;
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if (miso_received_nibbles == 2*miso_size) {
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if (miso_cb != 0) {
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miso_cb(miso_recvbuf, miso_size);
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}
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miso_state = 0;
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}
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}
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break;
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}
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}
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void paracomm_init(miso_cb_t cb) {
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mosi_size = 0;
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mosi_workbuf_idx = 0;
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mosi_workbuf_size = 0;
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mosi_state = 0;
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miso_state = 0;
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miso_cb = cb;
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}
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int paracomm_send(uint8_t b) {
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if (mosi_workbuf_size == 256) {
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return -1;
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}
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uint8_t* buff = mosi_workbuf[mosi_workbuf_idx];
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buff[mosi_workbuf_size] = b;
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mosi_workbuf_size += 1;
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return 0;
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}
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