src/main/drivers/transponder_ir_erlt.c

   1 /*
   2  * This file is part of Cleanflight and Betaflight.
   3  *
   4  * Cleanflight and Betaflight are free software. You can redistribute
   5  * this software and/or modify this software under the terms of the
   6  * GNU General Public License as published by the Free Software
   7  * Foundation, either version 3 of the License, or (at your option)
   8  * any later version.
   9  *
  10  * Cleanflight and Betaflight are distributed in the hope that they
  11  * will be useful, but WITHOUT ANY WARRANTY; without even the implied
  12  * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  13  * See the GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this software.
  17  *
  18  * If not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include <stdbool.h>
  22 #include <stdint.h>
  23 #include <string.h>
  24 #include "platform.h"
  25
  26 #ifdef USE_TRANSPONDER
  27
  28 #include "drivers/transponder_ir.h"
  29 #include "drivers/transponder_ir_erlt.h"
  30
  31 #if defined(STM32F3) || defined(STM32F4) || defined(STM32F7) || defined(STM32H7) || defined(STM32G4) || defined(UNIT_TEST)
  32
  33 static uint16_t dmaBufferOffset;
  34 extern const struct transponderVTable erltTansponderVTable;
  35
  36 void transponderIrInitERLT(transponder_t *transponder){
  37     transponder->dma_buffer_size    = TRANSPONDER_DMA_BUFFER_SIZE_ERLT;
  38     transponder->vTable             = &erltTansponderVTable;
  39     transponder->timer_hz           = TRANSPONDER_TIMER_MHZ_ERLT;
  40     transponder->timer_carrier_hz   = TRANSPONDER_CARRIER_HZ_ERLT;
  41     memset(&(transponder->transponderIrDMABuffer.erlt), 0, sizeof(transponder->transponderIrDMABuffer.erlt));
  42 }
  43
  44 void addBitToBuffer(transponder_t *transponder, uint8_t cycles, uint8_t pulsewidth)
  45 {
  46     for (int i = 0; i < cycles; i++) {
  47         transponder->transponderIrDMABuffer.erlt[dmaBufferOffset++] = pulsewidth;
  48     }
  49 }
  50
  51 void updateTransponderDMABufferERLT(transponder_t *transponder, const uint8_t* transponderData)
  52 {
  53     uint8_t byteToSend = ~(*transponderData); //transponderData is stored inverted, so invert before using
  54     uint8_t paritysum = 0; //sum of one bits
  55
  56     dmaBufferOffset = 0; //reset buffer count
  57
  58     //start bit 1, always pulsed, bit value = 0
  59     addBitToBuffer(transponder, ERLTCyclesForZeroBit, transponder->bitToggleOne);
  60
  61     //start bit 2, always not pulsed, bit value = 0
  62     addBitToBuffer(transponder, ERLTCyclesForZeroBit, ERLTBitQuiet);
  63
  64     //add data bits, only the 6 LSB
  65     for (int i = 5; i >= 0; i--)
  66     {
  67         uint8_t bv = (byteToSend >> i) & 0x01;
  68         paritysum += bv;
  69         addBitToBuffer(transponder, (bv ? ERLTCyclesForOneBit : ERLTCyclesForZeroBit), ((i % 2) ? transponder->bitToggleOne : ERLTBitQuiet));
  70     }
  71
  72     //parity bit, always pulsed, bit value is zero if sum is even, one if odd
  73     addBitToBuffer(transponder, ((paritysum % 2) ?  ERLTCyclesForOneBit : ERLTCyclesForZeroBit), transponder->bitToggleOne);
  74
  75     //add final zero after the pulsed parity bit to stop pulses until the next update
  76     transponder->transponderIrDMABuffer.erlt[dmaBufferOffset++] = ERLTBitQuiet;
  77
  78     //reset buffer size to that required by this ERLT id
  79     transponder->dma_buffer_size = dmaBufferOffset;
  80 }
  81
  82 const struct transponderVTable erltTansponderVTable = {
  83      updateTransponderDMABufferERLT,
  84 };
  85
  86 #endif
  87 #endif