src/main/drivers/rx/rx_xn297.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 // This file borrows heavily from project Deviation,
  22 // see http://deviationtx.com
  23
  24 #include <stdbool.h>
  25 #include <stdint.h>
  26
  27 #include "platform.h"
  28
  29 #if defined(USE_RX_XN297)
  30
  31 #include "common/crc.h"
  32
  33 #include "pg/rx.h"
  34
  35 #include "drivers/rx/rx_nrf24l01.h"
  36 #include "drivers/rx/rx_spi.h"
  37
  38
  39 static const uint8_t xn297_data_scramble[30] = {
  40     0xbc, 0xe5, 0x66, 0x0d, 0xae, 0x8c, 0x88, 0x12,
  41     0x69, 0xee, 0x1f, 0xc7, 0x62, 0x97, 0xd5, 0x0b,
  42     0x79, 0xca, 0xcc, 0x1b, 0x5d, 0x19, 0x10, 0x24,
  43     0xd3, 0xdc, 0x3f, 0x8e, 0xc5, 0x2f
  44 };
  45
  46 static const uint16_t xn297_crc_xorout[26] = {
  47     0x9BA7, 0x8BBB, 0x85E1, 0x3E8C, 0x451E, 0x18E6, 0x6B24, 0xE7AB,
  48     0x3828, 0x814B, 0xD461, 0xF494, 0x2503, 0x691D, 0xFE8B, 0x9BA7,
  49     0x8B17, 0x2920, 0x8B5F, 0x61B1, 0xD391, 0x7401, 0x2138, 0x129F,
  50     0xB3A0, 0x2988
  51 };
  52
  53 static uint8_t bitReverse(uint8_t bIn)
  54 {
  55     uint8_t bOut = 0;
  56     for (int ii = 0; ii < 8; ++ii) {
  57         bOut = (bOut << 1) | (bIn & 1);
  58         bIn >>= 1;
  59     }
  60     return bOut;
  61 }
  62
  63
  64 #define RX_TX_ADDR_LEN 5
  65
  66 uint16_t XN297_UnscramblePayload(uint8_t *data, int len, const uint8_t *rxAddr)
  67 {
  68     uint16_t crc = 0xb5d2;
  69     if (rxAddr) {
  70         for (int ii = 0; ii < RX_TX_ADDR_LEN; ++ii) {
  71             crc = crc16_ccitt(crc, rxAddr[RX_TX_ADDR_LEN - 1 - ii]);
  72         }
  73     }
  74     for (int ii = 0; ii < len; ++ii) {
  75         crc = crc16_ccitt(crc, data[ii]);
  76         data[ii] = bitReverse(data[ii] ^ xn297_data_scramble[ii]);
  77     }
  78     crc ^= xn297_crc_xorout[len];
  79     return crc;
  80 }
  81
  82 void XN297_WritePayload(uint8_t *data, int len, const uint8_t *rxAddr)
  83 {
  84     uint8_t packet[NRF24L01_MAX_PAYLOAD_SIZE];
  85     uint16_t crc = 0xb5d2;
  86     for (int ii = 0; ii < RX_TX_ADDR_LEN; ++ii) {
  87         packet[ii] = rxAddr[RX_TX_ADDR_LEN - 1 - ii];
  88         crc = crc16_ccitt(crc, packet[ii]);
  89     }
  90     for (int ii = 0; ii < len; ++ii) {
  91         const uint8_t bOut = bitReverse(data[ii]);
  92         packet[ii + RX_TX_ADDR_LEN] = bOut ^ xn297_data_scramble[ii];
  93         crc = crc16_ccitt(crc, packet[ii + RX_TX_ADDR_LEN]);
  94     }
  95     crc ^= xn297_crc_xorout[len];
  96     packet[RX_TX_ADDR_LEN + len] = crc >> 8;
  97     packet[RX_TX_ADDR_LEN + len + 1] = crc & 0xff;
  98     NRF24L01_WritePayload(packet, RX_TX_ADDR_LEN + len + 2);
  99 }
 100 #endif