diff options
Diffstat (limited to 'src/ootx_decoder.c')
-rw-r--r-- | src/ootx_decoder.c | 287 |
1 files changed, 287 insertions, 0 deletions
diff --git a/src/ootx_decoder.c b/src/ootx_decoder.c new file mode 100644 index 0000000..8ec16f2 --- /dev/null +++ b/src/ootx_decoder.c @@ -0,0 +1,287 @@ +// (C) 2017 Joshua Allen, MIT/x11 License. +// +//All MIT/x11 Licensed Code in this file may be relicensed freely under the GPL or LGPL licenses. + +/* ootx data decoder */ + +#include <stdio.h> +#include <stdlib.h> +#include <zlib.h> +#include <assert.h> +#include "ootx_decoder.h" +//#include "crc32.h" + +//char* fmt_str = "L Y HMD %d 5 1 206230 %d\n"; + +#define MAX_BUFF_SIZE 64 + +void (*ootx_packet_clbk)(ootx_decoder_context * ctx, ootx_packet* packet) = NULL; +void (*ootx_bad_crc_clbk)(ootx_decoder_context * ctx, ootx_packet* packet, uint32_t crc) = NULL; + +void ootx_pump_bit(ootx_decoder_context *ctx, uint8_t dbit); + +void ootx_init_decoder_context(ootx_decoder_context *ctx) { + ctx->buf_offset = 0; + ctx->bits_written = 0; + + ctx->preamble = 0XFFFFFFFF; + ctx->bits_processed = 0; + ctx->found_preamble = 0; + + ctx->buffer = (uint8_t*)malloc(MAX_BUFF_SIZE); + ctx->payload_size = (uint16_t*)ctx->buffer; + *(ctx->payload_size) = 0; +} + +void ootx_free_decoder_context(ootx_decoder_context *ctx) { + free(ctx->buffer); + ctx->buffer = NULL; + ctx->payload_size = NULL; +} + +uint8_t ootx_decode_bit(uint32_t length) { + uint8_t t = (length - 2750) / 500; //why 2750? +// return ((t & 0x02)>0)?0xFF:0x00; //easier if we need to bitshift right + return ((t & 0x02)>>1); +} + +uint8_t ootx_detect_preamble(ootx_decoder_context *ctx, uint8_t dbit) { + ctx->preamble <<= 1; +// ctx->preamble |= (0x01 & dbit); + ctx->preamble |= dbit; + if ((ctx->preamble & 0x0003ffff) == 0x00000001) return 1; + return 0; +} + +void ootx_reset_buffer(ootx_decoder_context *ctx) { + ctx->buf_offset = 0; + ctx->buffer[0] = 0; + ctx->bits_written = 0; + *(ctx->payload_size) = 0; +} + +void ootx_inc_buffer_offset(ootx_decoder_context *ctx) { + ++(ctx->buf_offset); + +// assert(ctx->buf_offset<MAX_BUFF_SIZE); + + /* the buffer is going to overflow, wrap the buffer and don't write more data until the preamble is found again */ + if(ctx->buf_offset>=MAX_BUFF_SIZE) { + ctx->buf_offset = 0; + ctx->found_preamble = 0; + } + + ctx->buffer[ctx->buf_offset] = 0; +} + +void ootx_write_to_buffer(ootx_decoder_context *ctx, uint8_t dbit) { + uint8_t *current_byte = ctx->buffer + ctx->buf_offset; + + *current_byte <<= 1; +// *current_byte |= (0x01 & dbit); + *current_byte |= dbit; + + ++(ctx->bits_written); + if (ctx->bits_written>7) { + ctx->bits_written=0; +// printf("%d\n", *current_byte); + ootx_inc_buffer_offset(ctx); + } +} + +uint8_t ootx_process_bit(ootx_decoder_context *ctx, uint32_t length) { + uint8_t dbit = ootx_decode_bit(length); + ootx_pump_bit( ctx, dbit ); + return dbit; +} + +void ootx_pump_bit(ootx_decoder_context *ctx, uint8_t dbit) { +// uint8_t dbit = ootx_decode_bit(length); + ++(ctx->bits_processed); + + if ( ootx_detect_preamble(ctx, dbit) ) { + /* data stream can start over at any time so we must + always look for preamble bits */ + //printf("Preamble found\n"); + ootx_reset_buffer(ctx); + ctx->bits_processed = 0; + ctx->found_preamble = 1; + } + else if(ctx->bits_processed>16) { + //every 17th bit needs to be dropped (sync bit) +// printf("drop %d\n", dbit); + if( !dbit ) + { + printf("Bad sync bit\n"); + ootx_reset_buffer(ctx); + } + ctx->bits_processed = 0; + } + else if (ctx->found_preamble > 0) + { + /* only write to buffer if the preamble is found. + if the buffer overflows, found_preamble will be cleared + and writing will stop. data would be corrupted, so there is no point in continuing + */ + + ootx_write_to_buffer(ctx, dbit); + + uint16_t padded_length = *(ctx->payload_size); + padded_length += (padded_length&0x01); //extra null byte if odd + +/* int k; + printf( ":" ); + for( k = 0; k < 36; k++ ) + { + printf( "%02x ", ctx->buffer[k] ); + } + printf( "\n" );*/ + + if (ctx->buf_offset >= (padded_length+6)) { + /* once we have a complete ootx packet, send it out in the callback */ + ootx_packet op; + + op.length = *(ctx->payload_size); + op.data = ctx->buffer+2; + op.crc32 = *(uint32_t*)(op.data+padded_length); + + uint32_t crc = crc32( 0L, Z_NULL, 0 ); + crc = crc32( crc, op.data,op.length); + + if (crc != op.crc32) { + if (ootx_bad_crc_clbk != NULL) ootx_bad_crc_clbk(ctx, &op,crc); + } + else if (ootx_packet_clbk != NULL) { + ootx_packet_clbk(ctx,&op); + } + + ootx_reset_buffer(ctx); + } + } +} + +uint8_t* get_ptr(uint8_t* data, uint8_t bytes, uint16_t* idx) { + uint8_t* x = data + *idx; + *idx += bytes; + return x; +} + +/* simply doing: +float f = 0; +uint32_t *ftmp = (uint32_t*)&f; //use the allocated floating point memory +This can cause problem when strict aliasing (-O2) is used. +Reads and writes to f and ftmp would be considered independent and could be +be reordered by the compiler. A union solves that problem. +*/ +union iFloat { + uint32_t i; + float f; +}; + +float _half_to_float(uint8_t* data) { + uint16_t x = *(uint16_t*)data; + union iFloat fnum; + fnum.f = 0; + + //sign + fnum.i = (x & 0x8000)<<16; + + if ((x & 0x7FFF) == 0) return fnum.f; //signed zero + + if ((x & 0x7c00) == 0) { + //denormalized + x = (x&0x3ff)<<1; //only mantissa, advance intrinsic bit forward + uint8_t e = 0; + //shift until intrinsic bit of mantissa overflows into exponent + //increment exponent each time + while ((x&0x0400) == 0) { + x<<=1; + e++; + } + fnum.i |= ((uint32_t)(112-e))<<23; //bias exponent to 127, half floats are biased 15 so only need to go 112 more. + fnum.i |= ((uint32_t)(x&0x3ff))<<13; //insert mantissa + return fnum.f; + } + + if((x&0x7c00) == 0x7c00) { + //for infinity, fraction is 0 + //for NaN, fraction is anything non zero + //we could just copy in bits and not shift, but the mantissa of a NaN can have meaning + fnum.i |= 0x7f800000 | ((uint32_t)(x & 0x3ff))<<13; + return fnum.f; + } + + fnum.i |= ((((uint32_t)(x & 0x7fff)) + 0x1c000u) << 13); + + return fnum.f; +} + +void init_lighthouse_info_v6(lighthouse_info_v6* lhi, uint8_t* data) { + uint16_t idx = 0; + /* + uint16_t fw_version;//Firmware version (bit 15..6), protocol version (bit 5..0) + uint32_t id; //Unique identifier of the base station + float fcal_0_phase; //"phase" for rotor 0 + float fcal_1_phase; //"phase" for rotor 1 + float fcal_0_tilt; //"tilt" for rotor 0 + float fcal_1_tilt; //"tilt" for rotor 1 + uint8_t sys_unlock_count; //Lowest 8 bits of the rotor desynchronization counter + uint8_t hw_version; //Hardware version + float fcal_0_curve; //"curve" for rotor 0 + float fcal_1_curve; //"curve" for rotor 1 + int8_t accel_dir_x; //"orientation vector" + int8_t accel_dir_y; //"orientation vector" + int8_t accel_dir_z; //"orientation vector" + float fcal_0_gibphase; //"gibbous phase" for rotor 0 (normalized angle) + float fcal_1_gibphase; //"gibbous phase" for rotor 1 (normalized angle) + float fcal_0_gibmag; //"gibbous magnitude" for rotor 0 + float fcal_1_gibmag; //"gibbous magnitude" for rotor 1 + uint8_t mode_current; //Currently selected mode (default: 0=A, 1=B, 2=C) + uint8_t sys_faults; //"fault detect flags" (should be 0) + */ + + lhi->fw_version = *(uint16_t*)get_ptr(data,sizeof(uint16_t),&idx); + lhi->id = *(uint32_t*)get_ptr(data,sizeof(uint32_t),&idx); + lhi->fcal_0_phase = _half_to_float( get_ptr(data,sizeof(uint16_t),&idx) ); + lhi->fcal_1_phase = _half_to_float( get_ptr(data,sizeof(uint16_t),&idx) ); + lhi->fcal_0_tilt = _half_to_float( get_ptr(data,sizeof(uint16_t),&idx) ); + lhi->fcal_1_tilt = _half_to_float( get_ptr(data,sizeof(uint16_t),&idx) ); + lhi->sys_unlock_count = *get_ptr(data,sizeof(uint8_t),&idx); + lhi->hw_version = *get_ptr(data,sizeof(uint8_t),&idx); + lhi->fcal_0_curve = _half_to_float( get_ptr(data,sizeof(uint16_t),&idx) ); + lhi->fcal_1_curve = _half_to_float( get_ptr(data,sizeof(uint16_t),&idx) ); + lhi->accel_dir_x = *(int8_t*)get_ptr(data,sizeof(uint8_t),&idx); + lhi->accel_dir_y = *(int8_t*)get_ptr(data,sizeof(uint8_t),&idx); + lhi->accel_dir_z = *(int8_t*)get_ptr(data,sizeof(uint8_t),&idx); + lhi->fcal_0_gibphase = _half_to_float( get_ptr(data,sizeof(uint16_t),&idx) ); + lhi->fcal_1_gibphase = _half_to_float( get_ptr(data,sizeof(uint16_t),&idx) ); + lhi->fcal_0_gibmag = _half_to_float( get_ptr(data,sizeof(uint16_t),&idx) ); + lhi->fcal_1_gibmag = _half_to_float( get_ptr(data,sizeof(uint16_t),&idx) ); + lhi->mode_current = *get_ptr(data,sizeof(uint8_t),&idx); + lhi->sys_faults = *get_ptr(data,sizeof(uint8_t),&idx); + +} + +void print_lighthouse_info_v6(lighthouse_info_v6* lhi) { + + printf("\t%X\n\t%X\n\t%f\n\t%f\n\t%f\n\t%f\n\t%d\n\t%d\n\t%f\n\t%f\n\t%d\n\t%d\n\t%d\n\t%f\n\t%f\n\t%f\n\t%f\n\t%d\n\t%d\n", + lhi->fw_version, + lhi->id, + lhi->fcal_0_phase, + lhi->fcal_1_phase, + lhi->fcal_0_tilt, + lhi->fcal_1_tilt, + lhi->sys_unlock_count, + lhi->hw_version, + lhi->fcal_0_curve, + lhi->fcal_1_curve, + lhi->accel_dir_x, + lhi->accel_dir_y, + lhi->accel_dir_z, + lhi->fcal_0_gibphase, + lhi->fcal_1_gibphase, + lhi->fcal_0_gibmag, + lhi->fcal_1_gibmag, + lhi->mode_current, + lhi->sys_faults); +} |