ESP32-PaxCounter/src/if482.cpp

/* NOTE:
The IF482 Generator needs an high precise 1 Hz clock signal which cannot be
acquired in suitable precision on the ESP32 SoC itself. Additional clocking
hardware is required, ususally the clock signal is generated by external RTC or
GPS which can generate a precise time pulse signal (+/- 2ppm).

In this example code we use a Maxim DS3231 RTC chip, and configure the chips's
interrupt output pin as clock. The clock signal triggers an interrupt on the
ESP32, which controls the realtime output of IF482 telegram. This is why code in
IF482.cpp depends on code in RTCTIME.cpp.
*/

///////////////////////////////////////////////////////////////////////////////

/*
IF482 Generator to control clocks with IF482 telegram input (e.g. BÜRK BU190)
   

Example IF482 telegram: "OAL160806F170400"

IF482 Specification:
http://www.mobatime.com/fileadmin/user_upload/downloads/TE-112023.pdf

The IF 482 telegram is a time telegram, which sends the time and date
information as ASCII characters through the serial interface RS 232 or RS 422.

Communication parameters:

Baud rate: 9600 Bit/s
Data bits 7
Parity: even
Stop bit: 1
Jitter: < 50ms

Interface : RS232 or RS422

Synchronization: Telegram ends at the beginning of the second
specified in the telegram

Cycle: 1 second

Format of ASCII telegram string:

Byte  Meaning             ASCII     Hex
 1    Start of telegram   O         4F
 2    Monitoring*         A         41
 3    Time-Season**       W/S/U/L   57 or 53
 4    Year tens           0 .. 9    30 .. 39
 5    Year unit           0 .. 9    30 .. 39
 6    Month tens          0 or 1    30 or 31
 7    Month unit          0 .. 9    30 .. 39
 8    Day tens            0 .. 3    30 .. 33
 9    Day unit            0 .. 9    30 .. 39
10    Day of week***      1 .. 7    31 .. 37
11    Hours tens          0 .. 2    30 .. 32
12    Hours unit          0 .. 9    30 .. 39
13    Minutes tens        0 .. 5    30 .. 35
14    Minutes unit        0 .. 9    30 .. 39
15    Seconds tens        0 .. 5    30 .. 35
16    Seconds unit        0 .. 9    30 .. 39
17    End of telegram     CR        0D

*) Monitoring:
With a correctly received time in the sender unit, the ASCII character 'A' is
issued. If 'M' is issued, this indicates that the sender was unable to receive
any time signal for over 12 hours (time is accepted with ‘A’ and ‘M’).

**) Season:
W: Standard time,
S: Season time,
U: UTC time (not supported by all systems),
L: Local Time

***) Day of week:
not evaluated by model BU-190

*/
///////////////////////////////////////////////////////////////////////////////

#ifdef HAS_IF482

#include "if482.h"

// Local logging tag
static const char TAG[] = "main";

HardwareSerial IF482(2); // use UART #2 (note: #1 may be in use for serial GPS)

// triggered by timepulse to ticker out DCF signal
void IF482_Pulse(time_t t) {

  static const TickType_t txDelay =
      pdMS_TO_TICKS(IF482_PULSE_LENGTH) - tx_Ticks(HAS_IF482);

  TickType_t startTime = xTaskGetTickCount();

  vTaskDelayUntil(&startTime, txDelay); // wait until moment to fire
  IF482.print(IF482_Frame(t + 1)); // note: if482 telegram for *next* second
}

String IRAM_ATTR IF482_Frame(time_t startTime) {

  time_t t = myTZ.toLocal(startTime);
  char mon, out[IF482_FRAME_SIZE];

  switch (timeStatus()) { // indicates if time has been set and recently synced
  case timeSet:           // time is set and is synced
    mon = 'A';
    break;
  case timeNeedsSync: // time had been set but sync attempt did not succeed
    mon = 'M';
    break;
  default: // unknown time status (should never be reached)
    mon = '?';
    break;
  } // switch

  // generate IF482 telegram
  snprintf(out, sizeof(out), "O%cL%02u%02u%02u%1u%02u%02u%02u\r", mon,
           year(t) - 2000, month(t), day(t), weekday(t), hour(t), minute(t),
           second(t));

  ESP_LOGD(TAG, "IF482 = %s", out);
  return out;
}

// calculate serial tx time from IF482 serial settings
TickType_t tx_Ticks(unsigned long baud, uint32_t config, int8_t rxPin,
                    int8_t txPins) {

  uint32_t databits = ((config & 0x0c) >> 2) + 5;
  uint32_t stopbits = ((config & 0x20) >> 5) + 1;
  uint32_t txTime =
      (databits + stopbits + 2) * IF482_FRAME_SIZE * 1000.0 / baud;
  // +2 ms margin for the startbit and the clock's processing time

  return pdMS_TO_TICKS(round(txTime));
}

#endif // HAS_IF482