Jiajun Zhang / Mbed OS DACandticker

LAB 3 DAC

Fork of DACandticker_sample by William Marsh

name.cpp@4:dc6e0fdcf6b4, 2018-02-15 (annotated)

Committer:
Bossman
Date:
Thu Feb 15 17:19:16 2018 +0000
Revision:
4:dc6e0fdcf6b4
Version 2

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Bossman 4:dc6e0fdcf6b4 1 // Revised for mbed 5
Bossman 4:dc6e0fdcf6b4 2
Bossman 4:dc6e0fdcf6b4 3 #include "mbed.h"
Bossman 4:dc6e0fdcf6b4 4 #include "sineTable.h"
Bossman 4:dc6e0fdcf6b4 5
Bossman 4:dc6e0fdcf6b4 6 Ticker tickout ; // Creates periodic interrupt
Bossman 4:dc6e0fdcf6b4 7 AnalogOut ao(PTE30) ; // Analog output
Bossman 4:dc6e0fdcf6b4 8
Bossman 4:dc6e0fdcf6b4 9 Ticker tick; // Ticker for reading analog
Bossman 4:dc6e0fdcf6b4 10 AnalogIn ain(A0) ; // Analog input
Bossman 4:dc6e0fdcf6b4 11 DigitalOut led1(LED_RED);
Bossman 4:dc6e0fdcf6b4 12
Bossman 4:dc6e0fdcf6b4 13
Bossman 4:dc6e0fdcf6b4 14 Serial pc(USBTX, USBRX); // tx, rx, for debugging
Bossman 4:dc6e0fdcf6b4 15
Bossman 4:dc6e0fdcf6b4 16 // Message type
Bossman 4:dc6e0fdcf6b4 17 typedef struct {
Bossman 4:dc6e0fdcf6b4 18 uint16_t analog; /* Analog input value */
Bossman 4:dc6e0fdcf6b4 19 } message_t;
Bossman 4:dc6e0fdcf6b4 20
Bossman 4:dc6e0fdcf6b4 21 // Mail box
Bossman 4:dc6e0fdcf6b4 22 Mail<message_t, 2> mailbox;
Bossman 4:dc6e0fdcf6b4 23
Bossman 4:dc6e0fdcf6b4 24 // Function called every 10ms to read ADC
Bossman 4:dc6e0fdcf6b4 25 // Low pass filter
Bossman 4:dc6e0fdcf6b4 26 // Every 10th value is sent to mailbox
Bossman 4:dc6e0fdcf6b4 27 volatile int samples = 0 ;
Bossman 4:dc6e0fdcf6b4 28 volatile uint16_t smoothed = 0 ;
Bossman 4:dc6e0fdcf6b4 29 void readA0() {
Bossman 4:dc6e0fdcf6b4 30 smoothed = (smoothed >> 1) + (ain.read_u16() >> 1) ;
Bossman 4:dc6e0fdcf6b4 31 samples++ ;
Bossman 4:dc6e0fdcf6b4 32 if (samples == 10) {
Bossman 4:dc6e0fdcf6b4 33 // send to thread
Bossman 4:dc6e0fdcf6b4 34 message_t *mess = mailbox.alloc() ; // may fail but does not block
Bossman 4:dc6e0fdcf6b4 35 if (mess) {
Bossman 4:dc6e0fdcf6b4 36 mess->analog = smoothed ;
Bossman 4:dc6e0fdcf6b4 37 mailbox.put(mess); // fails but does not block if full
Bossman 4:dc6e0fdcf6b4 38 }
Bossman 4:dc6e0fdcf6b4 39 samples = 0;
Bossman 4:dc6e0fdcf6b4 40 }
Bossman 4:dc6e0fdcf6b4 41 }
Bossman 4:dc6e0fdcf6b4 42
Bossman 4:dc6e0fdcf6b4 43 // Write voltage digits
Bossman 4:dc6e0fdcf6b4 44 // v Voltage as scale int, e.g. 3.30 is 330
Bossman 4:dc6e0fdcf6b4 45 void vToString(int v, char* s) {
Bossman 4:dc6e0fdcf6b4 46 s[3] = '0' + (v % 10) ;
Bossman 4:dc6e0fdcf6b4 47 v = v / 10 ;
Bossman 4:dc6e0fdcf6b4 48 s[2] = '0' + (v % 10) ;
Bossman 4:dc6e0fdcf6b4 49 v = v / 10 ;
Bossman 4:dc6e0fdcf6b4 50 s[0] = '0' + (v % 10) ;
Bossman 4:dc6e0fdcf6b4 51 }
Bossman 4:dc6e0fdcf6b4 52
Bossman 4:dc6e0fdcf6b4 53 volatile int index = 0 ; // index into array of sin values
Bossman 4:dc6e0fdcf6b4 54 void writeAout() {
Bossman 4:dc6e0fdcf6b4 55 ao.write_u16(sine[index]) ;
Bossman 4:dc6e0fdcf6b4 56 index = (index + 1) % 64 ;
Bossman 4:dc6e0fdcf6b4 57 }
Bossman 4:dc6e0fdcf6b4 58
Bossman 4:dc6e0fdcf6b4 59 // Main program
Bossman 4:dc6e0fdcf6b4 60 // Initialise variables
Bossman 4:dc6e0fdcf6b4 61 // Attach ISR for ticker
Bossman 4:dc6e0fdcf6b4 62 // Procss messages from mailbox
Bossman 4:dc6e0fdcf6b4 63 int main() {
Bossman 4:dc6e0fdcf6b4 64
Bossman 4:dc6e0fdcf6b4 65 int update_us = 1000 ;
Bossman 4:dc6e0fdcf6b4 66 int volts = 0;
Bossman 4:dc6e0fdcf6b4 67 led1 = 1 ; // turn off
Bossman 4:dc6e0fdcf6b4 68 // char vstring[] = "X.XX\r\n" ;
Bossman 4:dc6e0fdcf6b4 69
Bossman 4:dc6e0fdcf6b4 70 tick.attach_us(callback(&readA0), 10000); // ticks every 10ms
Bossman 4:dc6e0fdcf6b4 71
Bossman 4:dc6e0fdcf6b4 72
Bossman 4:dc6e0fdcf6b4 73 while (true)
Bossman 4:dc6e0fdcf6b4 74 {
Bossman 4:dc6e0fdcf6b4 75 osEvent evt = mailbox.get(); // wait for mail
Bossman 4:dc6e0fdcf6b4 76 if (evt.status == osEventMail)
Bossman 4:dc6e0fdcf6b4 77 {
Bossman 4:dc6e0fdcf6b4 78 message_t* mess = (message_t*)evt.value.p ;
Bossman 4:dc6e0fdcf6b4 79 volts = (mess->analog * 330) / 0xffff ;
Bossman 4:dc6e0fdcf6b4 80 mailbox.free(mess) ; // free the message space
Bossman 4:dc6e0fdcf6b4 81
Bossman 4:dc6e0fdcf6b4 82 update_us = 1000000/((1+(49*volts/330))*64) ;
Bossman 4:dc6e0fdcf6b4 83 tickout.detach() ;
Bossman 4:dc6e0fdcf6b4 84 tickout.attach_us(callback(&writeAout), update_us);
Bossman 4:dc6e0fdcf6b4 85 }
Bossman 4:dc6e0fdcf6b4 86
Bossman 4:dc6e0fdcf6b4 87 }
Bossman 4:dc6e0fdcf6b4 88 }