I will describe library functions used in the portable solar tracker project here:
The following functions are stored in the _myincludes.h file for inclusion by the main program. Since they are support programs and not necessary to understanding the program logic, they have been placed there in their entirety (there are no external C files to be included).
wait() is an often-used function which pauses program execution for sensors to adjust, registers to be updated, etc. millis may contain values from 0 to 65535. values over this delay indefinitely.
| void wait( uint16_t millis ){ while(millis--) _delay_ms(1); } |
I wote debug_d() and debug() to flash numbers on an LED for debugging. debug() can flash numbers within +/-32767.999. Reading the numbers takes a bit of practice, but is easy to do when it is understood that:
9 short (1/4 second) flashes indicate negative
1..9 is indicated by from one to nine (1/2second) flashes
0 is indicated by one long (1 second) flash
3 short flashes indicate a decimal point
leading/trailing zeros are suppressed
For example, –270.25 is [9 short][2][7][1 long][3 short][2][5]
Why do I have to do this? Because sometimes it is useful to show that a particular section of code is being executed, and as the Baby O has no built-in LCD panel, this provides a convenient and simple way to provide the user with feedback for debugging purposes. Note the use of the wait() function to allow the user time to mentally count the flashes...
NOTE: The debug_d() and debug() functions can be removed when a project is finalized.
| void debug_d(int digit) { /* pulse user LED on PC0 digit 1 to 9: 1 to 9 normal (250ms) pulses digit 0: one long (500ms) pulse digit 0xA (10): (decimal point) 3 short (125ms) pulses digit 0xB (11): (negative number) 9 short (125ms) pulses */ int long_delay = 0, short_delay = 0; if (digit == 0) {digit = 1; long_delay = 750;} if (digit == 0xA) {digit = 3; short_delay = -125;} if (digit == 0xB) {digit = 9; short_delay = -125;} while(digit--) { set_digital_output(IO_C0,HIGH); wait(250+long_delay+short_delay); set_digital_output(IO_C0,LOW); wait(250+short_delay); } wait(500); } int debug(double v) { /* pulse number using external LED on PC0 for debugging purposes calls debug_d() to pulse each digit, decimal point or sign, if negative ex: debug(-20.5) => [(9 short):2:(1 long):(3 short):5] pulses function returns 0 for OK, 1 for error numbers are rounded to 3 decimal places; function returns 1 numbers outside the range +|- MAX_VALUE will be truncated to +|- MAX_VALUE; function returns 0; numbers are leading|trailing zero suppressed, eg. debug(-0.70) <=> debug(-.7) => [9 long][3 short][7 medium] pulses */ int status = 1; long u6,u5,u4,u3,u2,u1, wp, dp; const double MAX_VALUE = 32767.999; if(v<0){v=-v;debug_d(0xB);} // flash that number is negative if (fabs(v)>MAX_VALUE) // exceeding supported limit flashes [-]MAX_VALUE, error status { v = MAX_VALUE; status = 0; } wp = floor(v); // whole part of number dp = round((v-wp)*10000/10); // decimal part u6 = floor(wp/100000); u5 = floor((wp-u6*100000)/10000); u4 = floor((wp-u6*100000-u5*10000)/1000); u3 = floor((wp-u6*100000-u5*10000-u4*1000)/100); u2 = floor((wp-u6*100000-u5*10000-u4*1000-u3*100)/10); u1 = wp-u6*100000-u5*10000-u4*1000-u3*100-u2*10; if(u6!=0) debug_d(u6); if(u6!=0 || u5!=0) debug_d(u5); if(u6!=0 || u5!=0 || u4!=0) debug_d(u4); if(u6!=0 || u5!=0 || u4!=0 || u3!=0) debug_d(u3); if(u6!=0 || u5!=0 || u4!=0 || u3!=0 || u2!=0) debug_d(u2); if((u6!=0 || u5!=0 || u4!=0 || u3!=0 || u2!=0 || u1!=0) || dp==0) debug_d(u1); // yes: 0, 20, -0; no: -0.23 // handle decimal part if (dp!=0) { debug_d(0xA); // flash decimal point u3 = floor(dp/100); u2 = floor((dp-u3*100)/10); u1 = dp-u3*100-u2*10; // no trailing zeros... if (u3!=0||u2!=0||u1!=0) debug_d(u3); // .001 if (u2!=0||u1!=0) debug_d(u2); if (u1!=0) debug_d(u1); } wait(2500); //pause between numbers return status; } |
| int switch_is_open(int pin) { /* test limit switch connected to any general i/o pin '..When the AVR powers up, all I/O pins are configured as inputs with their pull-up resistors disabled." Docs also say must set to PULL_UP_ENABLED before reading state pin ungrounded: is_digital_input_high() returns 1; pin grounded: is_digital_input_high() returns 0 */ set_digital_input(pin, PULL_UP_ENABLED); wait(100); return is_digital_input_high(pin); } |
The declination() function retrieves the declination values from a 4-point grid surrounding the position in question designated by its latitude and longitude, and returns an approximation of its declination. It uses a variation of ratios math called bilinear interpolation to estimate the declination. See: http://en.wikipedia.org/wiki/Bilinear_interpolation for a detailed explanation of this method.
The declination returned by this function is simply added to the bearing value returned by a compass IC, then adjusted to make sure the bearing is >= 0 and < 360 degrees--eg.:
:
bearing += declination(lat, lon);
return bearing >= 360 ? bearing - 360 : bearing < 0 ? bearing + 360 : bearing;
:
| float declination(float lat, float lon) { /* lookup declination values from 10 x 10 degree grid and return approximate declination for (lat,lon) data; 482 declination values (rounded to nearest degree) stored in 482 bytes */ // -60..0..60 step 10 => 2(6) + 1 = 13 dimensions for lat; -180..0..180 step 10 => 2(18) + 1 = 37 dimensions for lon char dec_tbl[13][37] = \ {46,45,44,42,41,40,38,36,33,28,23,16,10,4,-1,-5,-9,-14,-19,-26,-33,-40,-48,-55,-61, \ -66,-71,-74,-75,-72,-61,-25,22,40,45,47,46,30,30,30,30,29,29,29,29,27,24,18,11,3, \ -3,-9,-12,-15,-17,-21,-26,-32,-39,-45,-51,-55,-57,-56,-53,-44,-31,-14,0,13,21,26, \ 29,30,21,22,22,22,22,22,22,22,21,18,13,5,-3,-11,-17,-20,-21,-22,-23,-25,-29,-35, \ -40,-44,-45,-44,-40,-32,-22,-12,-3,3,9,14,18,20,21,16,17,17,17,17,17,16,16,16,13, \ 8,0,-9,-16,-21,-24,-25,-25,-23,-20,-21,-24,-28,-31,-31,-29,-24,-17,-9,-3,0,4,7, \ 10,13,15,16,12,13,13,13,13,13,12,12,11,9,3,-4,-12,-19,-23,-24,-24,-22,-17,-12,-9, \ -10,-13,-17,-18,-16,-13,-8,-3,0,1,3,6,8,10,12,12,10,10,10,10,10,10,10,9,9,6,0,-6, \ -14,-20,-22,-22,-19,-15,-10,-6,-2,-2,-4,-7,-8,-8,-7,-4,0,1,1,2,4,6,8,10,10,9,9,9, \ 9,9,9,8,8,7,4,-1,-8,-15,-19,-20,-18,-14,-9,-5,-2,0,1,0,-2,-3,-4,-3,-2,0,0,0,1,3,5, \ 7,8,9,8,8,8,9,9,9,8,8,6,2,-3,-9,-15,-18,-17,-14,-10,-6,-2,0,1,2,2,0,-1,-1,-2,-1,0, \ 0,0,0,1,3,5,7,8,8,9,9,10,10,10,10,8,5,0,-5,-11,-15,-16,-15,-12,-8,-4,-1,0,2,3,2,1,0, \ 0,0,0,0,-1,-2,-2,-1,0,3,6,8,6,9,10,11,12,12,11,9,5,0,-7,-12,-15,-15,-13,-10,-7,-3, \ 0,1,2,3,3,3,2,1,0,0,-1,-3,-4,-5,-5,-2,0,3,6,5,8,11,13,15,15,14,11,5,-1,-9,-14,-17, \ -16,-14,-11,-7,-3,0,1,3,4,5,5,5,4,3,1,-1,-4,-7,-8,-8,-6,-2,1,5,4,8,12,15,17,18,16, \ 12,5,-3,-12,-18,-20,-19,-16,-13,-8,-4,-1,1,4,6,8,9,9,9,7,3,-1,-6,-10,-12,-11,-9,-5, \ 0,4,3,9,14,17,20,21,19,14,4,-8,-19,-25,-26,-25,-21,-17,-12,-7,-2,1,5,9,13,15,16,16, \ 13,7,0,-7,-12,-15,-14,-11,-6,-1,3}; float decSW, decSE, decNW, decNE, decmin, decmax; float lonmin,latmin; short latmin_index,lonmin_index; /* set base point (latmin, lonmin) of grid */ /* no limits test on lon */ if (lon == 180) lonmin = 170; else lonmin = floor(lon/10)*10; /* supported lat's -60..60, so range check... */ if (lat >= 60) latmin = 50; else if (lat < -60) latmin = -60; else latmin = floor(lat/10)*10; /* array index = (degrees+[60|180])/10 */ latmin_index= (60+latmin)/10; lonmin_index= (180+lonmin)/10; decSW = dec_tbl[latmin_index][lonmin_index]; decSE = dec_tbl[latmin_index][lonmin_index+1]; decNE = dec_tbl[latmin_index+1][lonmin_index+1]; decNW = dec_tbl[latmin_index+1][lonmin_index]; /* approximate declination within the grid using bilinear interpolation */ decmin = (lon - lonmin) / 10 * (decSE - decSW) + decSW; decmax = (lon - lonmin) / 10 * (decNE - decNW) + decNW; return (lat - latmin) / 10 * (decmax - decmin) + decmin; } /* DIAGRAM OF 10X10 GRID SQUARE: (+60) (lon,latmin+10,decmax=?) l (lonmin,latmin+10,decNW) | | |(lonmin+10,latmin+10,decNE) a --o----x-------o-- t | | | i | | | t +----x(lon,lat,dec=?) u | | | d --o----x-------o-- e (lonmin,latmin,decSW) | | |(lonmin+10,latmin,decSE) (-60) (lon,latmin,decmin=?) (-180)<- longitude ->(+180) o = decs from table, x = calculated decs */ |
<< Contents < Main Functions
