Al Williams / Mbed 2 deprecated HAD_SigGen

Hackaday demo: Signal generator

Dependencies:   SDFileSystem mbed

output.cpp@1:c229c3ceb909, 2015-09-15 (annotated)

Committer:
wd5gnr
Date:
Tue Sep 15 15:21:34 2015 +0000
Revision:
1:c229c3ceb909
Parent:
0:8baa10bd07de 
Making sure all changes are ready for publication.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
wd5gnr 0:8baa10bd07de 1 #include "mbed.h"
wd5gnr 0:8baa10bd07de 2 #define _EXTERN_ extern
wd5gnr 0:8baa10bd07de 3 #include "main.h"
wd5gnr 0:8baa10bd07de 4 #include "output.h"
wd5gnr 0:8baa10bd07de 5
wd5gnr 0:8baa10bd07de 6
wd5gnr 0:8baa10bd07de 7 // Output "engines"
wd5gnr 0:8baa10bd07de 8
wd5gnr 0:8baa10bd07de 9 // Mbed timers are not reliable below a few dozen uS
wd5gnr 0:8baa10bd07de 10 // At one point I did this table but it is better to do a iinear regression
wd5gnr 0:8baa10bd07de 11 // for the whole range not just the ones that suffer from the timer jitters
wd5gnr 0:8baa10bd07de 12 // You would need to refigure the linear regression any time you change the loop but
wd5gnr 0:8baa10bd07de 13 // for the current setup (http://mycurvefit.com/ is handy for that)
wd5gnr 0:8baa10bd07de 14 #define M 23.79f
wd5gnr 0:8baa10bd07de 15 #define B -8.9878f
wd5gnr 0:8baa10bd07de 16
wd5gnr 0:8baa10bd07de 17 // If you want to set the M and B (see above) you can set CALIBRATE to 1
wd5gnr 0:8baa10bd07de 18 // and set M and B to 1.0 and 0. Then enter some different timebase
wd5gnr 0:8baa10bd07de 19 // values (t command) and measure the timing
wd5gnr 0:8baa10bd07de 20 // Then fit the curve using M and B
wd5gnr 0:8baa10bd07de 21 #define CALIBRATE 0
wd5gnr 0:8baa10bd07de 22
wd5gnr 0:8baa10bd07de 23
wd5gnr 0:8baa10bd07de 24 AnalogOut aout(DAC0_OUT); // Analog output
wd5gnr 0:8baa10bd07de 25
wd5gnr 0:8baa10bd07de 26
wd5gnr 0:8baa10bd07de 27 // inline assembly for nop (plus function call overhead)
wd5gnr 0:8baa10bd07de 28 void nop(void)
wd5gnr 0:8baa10bd07de 29 {
wd5gnr 0:8baa10bd07de 30 __ASM volatile("nop\n");
wd5gnr 0:8baa10bd07de 31 }
wd5gnr 0:8baa10bd07de 32
wd5gnr 0:8baa10bd07de 33
wd5gnr 0:8baa10bd07de 34 // Execution engines
wd5gnr 0:8baa10bd07de 35
wd5gnr 0:8baa10bd07de 36 static void exec0() // timebase == 0.0, go as fast as possible
wd5gnr 0:8baa10bd07de 37 {
wd5gnr 0:8baa10bd07de 38 while (1) {
wd5gnr 0:8baa10bd07de 39 aout.write_u16(buffer[bp]);
wd5gnr 0:8baa10bd07de 40 bp=(bp+1)&BUFSIZEMASK;
wd5gnr 0:8baa10bd07de 41 }
wd5gnr 0:8baa10bd07de 42 }
wd5gnr 0:8baa10bd07de 43
wd5gnr 0:8baa10bd07de 44 void exec() // All other time bases
wd5gnr 0:8baa10bd07de 45 {
wd5gnr 0:8baa10bd07de 46 unsigned i, newbase;
wd5gnr 0:8baa10bd07de 47 if (timebaseus==0) exec0(); // go as fast as possible -- never returns
wd5gnr 0:8baa10bd07de 48 #if CALIBRATE==1
wd5gnr 0:8baa10bd07de 49 float m=1.0f,b=0.0f;
wd5gnr 0:8baa10bd07de 50 pc.printf("Using M=%f B=%f\r\n",m,b);
wd5gnr 0:8baa10bd07de 51 newbase=(unsigned int)((m*timebaseus-b)+0.5f);
wd5gnr 0:8baa10bd07de 52 #else
wd5gnr 0:8baa10bd07de 53 newbase=(unsigned int)((M*timebaseus-B)+0.5f);
wd5gnr 0:8baa10bd07de 54 #endif
wd5gnr 0:8baa10bd07de 55 while (1) {
wd5gnr 0:8baa10bd07de 56 aout.write_u16(buffer[bp]);
wd5gnr 0:8baa10bd07de 57 bp=(bp+1)&BUFSIZEMASK;
wd5gnr 0:8baa10bd07de 58 for (i=0; i<newbase; i++) {
wd5gnr 0:8baa10bd07de 59 nop(); // could shave a little off maybe by moving inline here
wd5gnr 0:8baa10bd07de 60 }
wd5gnr 0:8baa10bd07de 61 }
wd5gnr 0:8baa10bd07de 62 }