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AP_Declination: save some more memory by putting the declination keys in progmem 

there was a comment saying this was too slow, but it actually costs
about 30 usec extra, which is trivial given the full auto declination
call costs 680 usec and its only called once per boot
This commit is contained in:
Andrew Tridgell 2012-03-30 13:45:22 +11:00
parent 70d4280935
commit 927834106d
1 changed files with 14 additions and 14 deletions
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28
libraries/AP_Declination/AP_Declination.cpp
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@ -7,11 +7,11 @@
* Scott Ferguson
* scottfromscott@gmail.com
*
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License
as published by the Free Software Foundation; either version 2.1
of the License, or (at your option) any later version.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2.1
* of the License, or (at your option) any later version.
*/
#include <FastSerial.h>
@ -65,9 +65,7 @@ static const uint8_t exception_signs[10][10] PROGMEM = \
};
// 76 bytes
// I decided NOT to store this in PROGMEM because it is small and the expense of pulling
// the value out of the PROGMEM is too high
static const uint8_t declination_keys[2][37] = \
static const uint8_t declination_keys[2][37] PROGMEM = \
{ \
// Row start values
{36,30,25,21,18,16,14,12,11,10,9,9,9,8,8,8,7,6,6,5,4,4,4,3,4,4,4}, \
@ -107,6 +105,8 @@ static const row_value declination_values[] PROGMEM = \
{0,0,0},{3,0,5},{2,0,1},{1,0,0},{0,0,0},{1,1,0},{2,1,0},{5,1,0},{8,1,0},{12,1,0},{14,1,0},{13,1,0},{9,1,0},{6,1,0},{3,1,0},{1,1,0},{0,0,0},{2,0,0},{1,0,0},{3,0,0},{2,0,0},{3,0,0},{4,0,0},{3,0,1},{4,0,0},{3,0,0},{4,0,1},{3,0,0},{4,0,0},{3,0,2},{4,0,0},{3,0,1},{4,0,0},{3,0,0},{2,0,0},{3,0,0},{2,0,2},{0,0,1},{1,1,0},{2,1,0},{4,1,0},{5,1,0},{7,1,0},{8,1,0},{6,1,1},{5,1,0},{3,1,0},{1,1,1},{1,0,1},{2,0,0},{3,0,0},{2,0,0},{3,0,1},{2,0,0},{3,0,0}, \
};
#define PGM_UINT8(p) (uint8_t)pgm_read_byte_far(p)
float
AP_Declination::get_declination(float lat, float lon)
{
@ -149,10 +149,10 @@ AP_Declination::get_lookup_value(uint8_t x, uint8_t y)
if(x >= 34) x -= 27;
// Read the unsigned value from the array
val = (uint8_t)pgm_read_byte_far(&exceptions[x][y]);
val = PGM_UINT8(&exceptions[x][y]);
// Read the 8 bit compressed sign values
uint8_t sign = (uint8_t)pgm_read_byte_far(&exception_signs[x][y/8]);
uint8_t sign = PGM_UINT8(&exception_signs[x][y/8]);
// Check the sign bit for this index
if(sign & (0x80 >> y%8))
@ -169,7 +169,7 @@ AP_Declination::get_lookup_value(uint8_t x, uint8_t y)
// If we are looking for the first value we can just use the
// row start value from declination_keys
if(y == 0) return declination_keys[0][x];
if(y == 0) return PGM_UINT8(&declination_keys[0][x]);
// Init vars
row_value stval;
@ -182,16 +182,16 @@ AP_Declination::get_lookup_value(uint8_t x, uint8_t y)
uint16_t start_index = 0, i;
// Init value to row start
val = declination_keys[0][x];
val = PGM_UINT8(&declination_keys[0][x]);
// Find the first element in the 1D array
// that corresponds with the target row
for(i = 0; i < x; i++){
start_index += declination_keys[1][i];
start_index += PGM_UINT8(&declination_keys[1][i]);
}
// Traverse the row until we find our value
for(i = start_index; i < (start_index + declination_keys[1][x]) && current_virtual_index <= y; i++){
for(i = start_index; i < (start_index + PGM_UINT8(&declination_keys[1][x])) && current_virtual_index <= y; i++){
// Pull out the row_value struct
memcpy_P((void*) &stval, (const prog_char *)&declination_values[i], sizeof(struct row_value));