src/lib/Handset/PPMHandset.cpp

   1 #include "targets.h"
   2
   3 #if defined(PLATFORM_ESP32) && defined(TARGET_TX)
   4
   5 #include "PPMHandset.h"
   6 #include "common.h"
   7 #include "crsf_protocol.h"
   8 #include "logging.h"
   9
  10 #include <driver/rmt.h>
  11
  12 constexpr auto RMT_TICKS_PER_US = 4;
  13
  14 void PPMHandset::Begin()
  15 {
  16     constexpr auto divisor = 80 / RMT_TICKS_PER_US;
  17
  18     rmt_config_t rmt_rx_config = RMT_DEFAULT_CONFIG_RX(static_cast<gpio_num_t>(GPIO_PIN_RCSIGNAL_RX), PPM_RMT_CHANNEL);
  19     rmt_rx_config.clk_div = divisor;
  20     rmt_rx_config.rx_config.idle_threshold = min(65000, RMT_TICKS_PER_US * 4000); // greater than 4ms triggers end of frame
  21     rmt_config(&rmt_rx_config);
  22     rmt_driver_install(PPM_RMT_CHANNEL, 1000, 0);
  23
  24     rmt_get_ringbuf_handle(PPM_RMT_CHANNEL, &rb);
  25     rmt_rx_start(PPM_RMT_CHANNEL, true);
  26     lastPPM = 0;
  27
  28     if (connected)
  29     {
  30         connected();
  31     }
  32 }
  33
  34 void PPMHandset::End()
  35 {
  36     rmt_driver_uninstall(PPM_RMT_CHANNEL);
  37 }
  38
  39 bool PPMHandset::IsArmed()
  40 {
  41     bool maybeArmed = numChannels < 5 || CRSF_to_BIT(ChannelData[4]);
  42     return maybeArmed && lastPPM;
  43 }
  44
  45 void PPMHandset::handleInput()
  46 {
  47     const auto now = millis();
  48     size_t length = 0;
  49
  50     auto *items = static_cast<rmt_item32_t *>(xRingbufferReceive(rb, &length, 0));
  51     if (items)
  52     {
  53         length /= 4; // one RMT = 4 Bytes
  54         int channelCount = 0;
  55         for (int i = 0; i < length; i++)
  56         {
  57             const auto item = items[i];
  58             // Stop if there is a 0 duration
  59             if (item.duration0 == 0 || item.duration1 == 0)
  60             {
  61                 break;
  62             }
  63             channelCount ++;
  64             const auto ppm = (item.duration0 + item.duration1) / RMT_TICKS_PER_US;
  65             ChannelData[i] = fmap(ppm, 988, 2012, CRSF_CHANNEL_VALUE_MIN, CRSF_CHANNEL_VALUE_MAX);
  66         }
  67         numChannels = channelCount;
  68         vRingbufferReturnItem(rb, static_cast<void *>(items));
  69         lastPPM = now;
  70     }
  71     else if (lastPPM && now - 1000 > lastPPM)
  72     {
  73         DBGLN("PPM signal lost, disarming");
  74         if (disconnected)
  75         {
  76             disconnected();
  77         }
  78         lastPPM = 0;
  79     }
  80 }
  81
  82 #endif