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betaflight/src/main/blackbox/blackbox_encoding.c

490 lines
14 KiB
C
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#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include "platform.h"
#ifdef USE_BLACKBOX
#include "blackbox_encoding.h"
#include "blackbox_io.h"
#include "common/encoding.h"
#include "common/printf.h"
static void _putc(void *p, char c)
{
(void)p;
blackboxWrite(c);
}
static int blackboxPrintfv(const char *fmt, va_list va)
{
return tfp_format(NULL, _putc, fmt, va);
}
//printf() to the blackbox serial port with no blocking shenanigans (so it's caller's responsibility to not write too fast!)
int blackboxPrintf(const char *fmt, ...)
{
va_list va;
va_start(va, fmt);
const int written = blackboxPrintfv(fmt, va);
va_end(va);
return written;
}
/*
* printf a Blackbox header line with a leading "H " and trailing "\n" added automatically. blackboxHeaderBudget is
* decreased to account for the number of bytes written.
*/
void blackboxPrintfHeaderLine(const char *name, const char *fmt, ...)
{
va_list va;
blackboxWrite('H');
blackboxWrite(' ');
blackboxWriteString(name);
blackboxWrite(':');
va_start(va, fmt);
const int written = blackboxPrintfv(fmt, va);
va_end(va);
blackboxWrite('\n');
blackboxHeaderBudget -= written + 3;
}
/**
* Write an unsigned integer to the blackbox serial port using variable byte encoding.
*/
void blackboxWriteUnsignedVB(uint32_t value)
{
//While this isn't the final byte (we can only write 7 bits at a time)
while (value > 127) {
blackboxWrite((uint8_t) (value | 0x80)); // Set the high bit to mean "more bytes follow"
value >>= 7;
}
blackboxWrite(value);
}
/**
* Write a signed integer to the blackbox serial port using ZigZig and variable byte encoding.
*/
void blackboxWriteSignedVB(int32_t value)
{
//ZigZag encode to make the value always positive
blackboxWriteUnsignedVB(zigzagEncode(value));
}
void blackboxWriteSignedVBArray(int32_t *array, int count)
{
for (int i = 0; i < count; i++) {
blackboxWriteSignedVB(array[i]);
}
}
void blackboxWriteSigned16VBArray(int16_t *array, int count)
{
for (int i = 0; i < count; i++) {
blackboxWriteSignedVB(array[i]);
}
}
void blackboxWriteS16(int16_t value)
{
blackboxWrite(value & 0xFF);
blackboxWrite((value >> 8) & 0xFF);
}
/**
* Write a 2 bit tag followed by 3 signed fields of 2, 4, 6 or 32 bits
*/
void blackboxWriteTag2_3S32(int32_t *values)
{
static const int NUM_FIELDS = 3;
//Need to be enums rather than const ints if we want to switch on them (due to being C)
enum {
BITS_2 = 0,
BITS_4 = 1,
BITS_6 = 2,
BITS_32 = 3
};
enum {
BYTES_1 = 0,
BYTES_2 = 1,
BYTES_3 = 2,
BYTES_4 = 3
};
int selector = BITS_2, selector2;
/*
* Find out how many bits the largest value requires to encode, and use it to choose one of the packing schemes
* below:
*
* Selector possibilities
*
* 2 bits per field ss11 2233,
* 4 bits per field ss00 1111 2222 3333
* 6 bits per field ss11 1111 0022 2222 0033 3333
* 32 bits per field sstt tttt followed by fields of various byte counts
*/
for (int x = 0; x < NUM_FIELDS; x++) {
//Require more than 6 bits?
if (values[x] >= 32 || values[x] < -32) {
selector = BITS_32;
break;
}
//Require more than 4 bits?
if (values[x] >= 8 || values[x] < -8) {
if (selector < BITS_6) {
selector = BITS_6;
}
} else if (values[x] >= 2 || values[x] < -2) { //Require more than 2 bits?
if (selector < BITS_4) {
selector = BITS_4;
}
}
}
switch (selector) {
case BITS_2:
blackboxWrite((selector << 6) | ((values[0] & 0x03) << 4) | ((values[1] & 0x03) << 2) | (values[2] & 0x03));
break;
case BITS_4:
blackboxWrite((selector << 6) | (values[0] & 0x0F));
blackboxWrite((values[1] << 4) | (values[2] & 0x0F));
break;
case BITS_6:
blackboxWrite((selector << 6) | (values[0] & 0x3F));
blackboxWrite((uint8_t)values[1]);
blackboxWrite((uint8_t)values[2]);
break;
case BITS_32:
/*
* Do another round to compute a selector for each field, assuming that they are at least 8 bits each
*
* Selector2 field possibilities
* 0 - 8 bits
* 1 - 16 bits
* 2 - 24 bits
* 3 - 32 bits
*/
selector2 = 0;
//Encode in reverse order so the first field is in the low bits:
for (int x = NUM_FIELDS - 1; x >= 0; x--) {
selector2 <<= 2;
if (values[x] < 128 && values[x] >= -128) {
selector2 |= BYTES_1;
} else if (values[x] < 32768 && values[x] >= -32768) {
selector2 |= BYTES_2;
} else if (values[x] < 8388608 && values[x] >= -8388608) {
selector2 |= BYTES_3;
} else {
selector2 |= BYTES_4;
}
}
//Write the selectors
blackboxWrite((selector << 6) | selector2);
//And now the values according to the selectors we picked for them
for (int x = 0; x < NUM_FIELDS; x++, selector2 >>= 2) {
switch (selector2 & 0x03) {
case BYTES_1:
blackboxWrite(values[x]);
break;
case BYTES_2:
blackboxWrite(values[x]);
blackboxWrite(values[x] >> 8);
break;
case BYTES_3:
blackboxWrite(values[x]);
blackboxWrite(values[x] >> 8);
blackboxWrite(values[x] >> 16);
break;
case BYTES_4:
blackboxWrite(values[x]);
blackboxWrite(values[x] >> 8);
blackboxWrite(values[x] >> 16);
blackboxWrite(values[x] >> 24);
break;
}
}
break;
}
}
/**
* Write a 2 bit tag followed by 3 signed fields of 2, 554, 877 or 32 bits
*/
int blackboxWriteTag2_3SVariable(int32_t *values)
{
static const int FIELD_COUNT = 3;
enum {
BITS_2 = 0,
BITS_554 = 1,
BITS_877 = 2,
BITS_32 = 3
};
enum {
BYTES_1 = 0,
BYTES_2 = 1,
BYTES_3 = 2,
BYTES_4 = 3
};
/*
* Find out how many bits the largest value requires to encode, and use it to choose one of the packing schemes
* below:
*
* Selector possibilities
*
* 2 bits per field ss11 2233,
* 554 bits per field ss11 1112 2222 3333
* 877 bits per field ss11 1111 1122 2222 2333 3333
* 32 bits per field sstt tttt followed by fields of various byte counts
*/
int selector = BITS_2;
int selector2 = 0;
// Require more than 877 bits?
if (values[0] >= 256 || values[0] < -256
|| values[1] >= 128 || values[1] < -128
|| values[2] >= 128 || values[2] < -128) {
selector = BITS_32;
// Require more than 554 bits?
} else if (values[0] >= 16 || values[0] < -16
|| values[1] >= 16 || values[1] < -16
|| values[2] >= 8 || values[2] < -8) {
selector = BITS_877;
// Require more than 2 bits?
} else if (values[0] >= 2 || values[0] < -2
|| values[1] >= 2 || values[1] < -2
|| values[2] >= 2 || values[2] < -2) {
selector = BITS_554;
}
switch (selector) {
case BITS_2:
blackboxWrite((selector << 6) | ((values[0] & 0x03) << 4) | ((values[1] & 0x03) << 2) | (values[2] & 0x03));
break;
case BITS_554:
// 554 bits per field ss11 1112 2222 3333
blackboxWrite((selector << 6) | ((values[0] & 0x1F) << 1) | ((values[1] & 0x1F) >> 4));
blackboxWrite(((values[1] & 0x0F) << 4) | (values[2] & 0x0F));
break;
case BITS_877:
// 877 bits per field ss11 1111 1122 2222 2333 3333
blackboxWrite((selector << 6) | ((values[0] & 0xFF) >> 2));
blackboxWrite(((values[0] & 0x03) << 6) | ((values[1] & 0x7F) >> 1));
blackboxWrite(((values[1] & 0x01) << 7) | (values[2] & 0x7F));
break;
case BITS_32:
/*
* Do another round to compute a selector for each field, assuming that they are at least 8 bits each
*
* Selector2 field possibilities
* 0 - 8 bits
* 1 - 16 bits
* 2 - 24 bits
* 3 - 32 bits
*/
selector2 = 0;
//Encode in reverse order so the first field is in the low bits:
for (int x = FIELD_COUNT - 1; x >= 0; x--) {
selector2 <<= 2;
if (values[x] < 128 && values[x] >= -128) {
selector2 |= BYTES_1;
} else if (values[x] < 32768 && values[x] >= -32768) {
selector2 |= BYTES_2;
} else if (values[x] < 8388608 && values[x] >= -8388608) {
selector2 |= BYTES_3;
} else {
selector2 |= BYTES_4;
}
}
//Write the selectors
blackboxWrite((selector << 6) | selector2);
//And now the values according to the selectors we picked for them
for (int x = 0; x < FIELD_COUNT; x++, selector2 >>= 2) {
switch (selector2 & 0x03) {
case BYTES_1:
blackboxWrite(values[x]);
break;
case BYTES_2:
blackboxWrite(values[x]);
blackboxWrite(values[x] >> 8);
break;
case BYTES_3:
blackboxWrite(values[x]);
blackboxWrite(values[x] >> 8);
blackboxWrite(values[x] >> 16);
break;
case BYTES_4:
blackboxWrite(values[x]);
blackboxWrite(values[x] >> 8);
blackboxWrite(values[x] >> 16);
blackboxWrite(values[x] >> 24);
break;
}
}
break;
}
return selector;
}
/**
* Write an 8-bit selector followed by four signed fields of size 0, 4, 8 or 16 bits.
*/
void blackboxWriteTag8_4S16(int32_t *values)
{
//Need to be enums rather than const ints if we want to switch on them (due to being C)
enum {
FIELD_ZERO = 0,
FIELD_4BIT = 1,
FIELD_8BIT = 2,
FIELD_16BIT = 3
};
uint8_t selector = 0;
//Encode in reverse order so the first field is in the low bits:
for (int x = 3; x >= 0; x--) {
selector <<= 2;
if (values[x] == 0) {
selector |= FIELD_ZERO;
} else if (values[x] < 8 && values[x] >= -8) {
selector |= FIELD_4BIT;
} else if (values[x] < 128 && values[x] >= -128) {
selector |= FIELD_8BIT;
} else {
selector |= FIELD_16BIT;
}
}
blackboxWrite(selector);
int nibbleIndex = 0;
uint8_t buffer = 0;
for (int x = 0; x < 4; x++, selector >>= 2) {
switch (selector & 0x03) {
case FIELD_ZERO:
//No-op
break;
case FIELD_4BIT:
if (nibbleIndex == 0) {
//We fill high-bits first
buffer = values[x] << 4;
nibbleIndex = 1;
} else {
blackboxWrite(buffer | (values[x] & 0x0F));
nibbleIndex = 0;
}
break;
case FIELD_8BIT:
if (nibbleIndex == 0) {
blackboxWrite(values[x]);
} else {
//Write the high bits of the value first (mask to avoid sign extension)
blackboxWrite(buffer | ((values[x] >> 4) & 0x0F));
//Now put the leftover low bits into the top of the next buffer entry
buffer = values[x] << 4;
}
break;
case FIELD_16BIT:
if (nibbleIndex == 0) {
//Write high byte first
blackboxWrite(values[x] >> 8);
blackboxWrite(values[x]);
} else {
//First write the highest 4 bits
blackboxWrite(buffer | ((values[x] >> 12) & 0x0F));
// Then the middle 8
blackboxWrite(values[x] >> 4);
//Only the smallest 4 bits are still left to write
buffer = values[x] << 4;
}
break;
}
}
//Anything left over to write?
if (nibbleIndex == 1) {
blackboxWrite(buffer);
}
}
/**
* Write `valueCount` fields from `values` to the Blackbox using signed variable byte encoding. A 1-byte header is
* written first which specifies which fields are non-zero (so this encoding is compact when most fields are zero).
*
* valueCount must be 8 or less.
*/
void blackboxWriteTag8_8SVB(int32_t *values, int valueCount)
{
uint8_t header;
if (valueCount > 0) {
//If we're only writing one field then we can skip the header
if (valueCount == 1) {
blackboxWriteSignedVB(values[0]);
} else {
//First write a one-byte header that marks which fields are non-zero
header = 0;
// First field should be in low bits of header
for (int i = valueCount - 1; i >= 0; i--) {
header <<= 1;
if (values[i] != 0) {
header |= 0x01;
}
}
blackboxWrite(header);
for (int i = 0; i < valueCount; i++) {
if (values[i] != 0) {
blackboxWriteSignedVB(values[i]);
}
}
}
}
}
/** Write unsigned integer **/
void blackboxWriteU32(int32_t value)
{
blackboxWrite(value & 0xFF);
blackboxWrite((value >> 8) & 0xFF);
blackboxWrite((value >> 16) & 0xFF);
blackboxWrite((value >> 24) & 0xFF);
}
/** Write float value in the integer form **/
void blackboxWriteFloat(float value)
{
blackboxWriteU32(castFloatBytesToInt(value));
}
#endif // BLACKBOX
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