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/*
* Dual sense: CDT (Signal) + RXD packet heuristic (edges + HDLC 0x7E).
* SPDX-License-Identifier: GPL-3.0-or-later
*/
#include "sense.h"
#include "board_pins.h"
#include "config.h"
#include "hardware/gpio.h"
#include "pico/stdlib.h"
#include <stdint.h>
static bool g_signal;
static bool g_packet;
static bool g_flag;
static absolute_time_t g_packet_until;
static absolute_time_t g_window_start;
static uint16_t g_edges;
static bool g_last_rxd;
static bool g_hold_valid;
static void try_flag_sample(void)
{
uint16_t sh = 0;
for (int i = 0; i < 16; i++) {
bool b = gpio_get(PIN_MODEM_RXD);
sh = (uint16_t)((sh << 1) | (b ? 1u : 0u));
if ((uint8_t)(sh & 0xFFu) == 0x7Eu) {
g_flag = true;
return;
}
sleep_us(833);
}
}
void sense_init(void)
{
g_signal = false;
g_packet = false;
g_flag = false;
g_hold_valid = false;
g_window_start = get_absolute_time();
g_edges = 0;
g_last_rxd = gpio_get(PIN_MODEM_RXD);
}
void sense_poll(void)
{
const c1224_config_t *cfg = config_get();
bool cdt = gpio_get(PIN_MODEM_CDT);
g_signal = cfg->cdt_active_high ? cdt : !cdt;
bool rxd = gpio_get(PIN_MODEM_RXD);
if (rxd != g_last_rxd) {
g_edges++;
g_last_rxd = rxd;
}
uint32_t win_ms = cfg->packet_window_ms ? cfg->packet_window_ms : 50;
if (absolute_time_diff_us(g_window_start, get_absolute_time()) >=
(int64_t)win_ms * 1000) {
if (g_edges >= cfg->packet_edge_min) {
g_flag = false;
try_flag_sample();
g_packet_until = make_timeout_time_ms(
cfg->packet_hold_ms ? cfg->packet_hold_ms : 500);
g_hold_valid = true;
}
g_edges = 0;
g_window_start = get_absolute_time();
}
if (g_hold_valid) {
if (time_reached(g_packet_until)) {
g_hold_valid = false;
g_packet = false;
g_flag = false;
} else {
g_packet = true;
}
} else {
g_packet = false;
}
}
bool sense_signal_active(void)
{
return g_signal;
}
bool sense_packet_active(void)
{
return g_packet;
}
bool sense_packet_flag(void)
{
return g_flag;
}
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