Haozun Sun / Mbed OS ADC_HaozunSun_180773877

ADC

main.cpp@3:f5d7fddeef39, 2019-01-31 (annotated)

Committer:
WilliamMarshQMUL
Date:
Thu Jan 31 11:10:30 2019 +0000
Revision:
3:f5d7fddeef39
Parent:
1:126dd2f5fc2d
Child:
4:ebd00f94455a
Version with thread instead of ticker

Who changed what in which revision?

UserRevisionLine numberNew contents of line
WilliamMarshQMUL 0:ad3cdc525b99 1
WilliamMarshQMUL 0:ad3cdc525b99 2 // LAB 3 SAMPLE PROGRAM 1
WilliamMarshQMUL 3:f5d7fddeef39 3 // Revised for mbed 5
WilliamMarshQMUL 0:ad3cdc525b99 4
WilliamMarshQMUL 0:ad3cdc525b99 5 #include "mbed.h"
WilliamMarshQMUL 1:126dd2f5fc2d 6
WilliamMarshQMUL 0:ad3cdc525b99 7
WilliamMarshQMUL 0:ad3cdc525b99 8 Ticker tick; // Ticker for reading analog
WilliamMarshQMUL 0:ad3cdc525b99 9 AnalogIn ain(A0) ; // Analog input
WilliamMarshQMUL 0:ad3cdc525b99 10 DigitalOut led1(LED_RED); // Red LED
WilliamMarshQMUL 3:f5d7fddeef39 11 DigitalOut led2(LED_BLUE); // BLUE LED
WilliamMarshQMUL 0:ad3cdc525b99 12
WilliamMarshQMUL 0:ad3cdc525b99 13 Serial pc(USBTX, USBRX); // tx, rx, for debugging
WilliamMarshQMUL 0:ad3cdc525b99 14
WilliamMarshQMUL 3:f5d7fddeef39 15 // Variable for a second thread
WilliamMarshQMUL 3:f5d7fddeef39 16 Thread ADCthread;
WilliamMarshQMUL 3:f5d7fddeef39 17
WilliamMarshQMUL 0:ad3cdc525b99 18 // Message type
WilliamMarshQMUL 0:ad3cdc525b99 19 typedef struct {
WilliamMarshQMUL 0:ad3cdc525b99 20 uint16_t analog; /* Analog input value */
WilliamMarshQMUL 0:ad3cdc525b99 21 } message_t;
WilliamMarshQMUL 0:ad3cdc525b99 22
WilliamMarshQMUL 0:ad3cdc525b99 23 // Mail box
WilliamMarshQMUL 0:ad3cdc525b99 24 Mail<message_t, 2> mailbox;
WilliamMarshQMUL 0:ad3cdc525b99 25
WilliamMarshQMUL 0:ad3cdc525b99 26 // Function called every 10ms to read ADC
WilliamMarshQMUL 0:ad3cdc525b99 27 // Low pass filter
WilliamMarshQMUL 0:ad3cdc525b99 28 // Every 10th value is sent to mailbox
WilliamMarshQMUL 0:ad3cdc525b99 29 void readA0() {
WilliamMarshQMUL 3:f5d7fddeef39 30 int samples = 0 ;
WilliamMarshQMUL 3:f5d7fddeef39 31 uint16_t smoothed = 0 ;
WilliamMarshQMUL 3:f5d7fddeef39 32 while (true) {
WilliamMarshQMUL 3:f5d7fddeef39 33 wait(0.01) ; // every 10 ms
WilliamMarshQMUL 3:f5d7fddeef39 34 led2 = 1 ;
WilliamMarshQMUL 3:f5d7fddeef39 35 smoothed = (smoothed >> 1) + (ain.read_u16() >> 1) ;
WilliamMarshQMUL 3:f5d7fddeef39 36 samples++ ;
WilliamMarshQMUL 3:f5d7fddeef39 37 if (samples == 10) {
WilliamMarshQMUL 3:f5d7fddeef39 38 // send to thread
WilliamMarshQMUL 3:f5d7fddeef39 39 message_t *mess = mailbox.alloc() ; // may fail but does not block
WilliamMarshQMUL 3:f5d7fddeef39 40 if (mess) {
WilliamMarshQMUL 3:f5d7fddeef39 41 mess->analog = smoothed ;
WilliamMarshQMUL 3:f5d7fddeef39 42 mailbox.put(mess); // fails but does not block if full
WilliamMarshQMUL 3:f5d7fddeef39 43 }
WilliamMarshQMUL 3:f5d7fddeef39 44 samples = 0;
WilliamMarshQMUL 0:ad3cdc525b99 45 }
WilliamMarshQMUL 0:ad3cdc525b99 46 }
WilliamMarshQMUL 0:ad3cdc525b99 47 }
WilliamMarshQMUL 0:ad3cdc525b99 48
WilliamMarshQMUL 0:ad3cdc525b99 49 // Write voltage digits
WilliamMarshQMUL 0:ad3cdc525b99 50 // v Voltage as scale int, e.g. 3.30 is 330
WilliamMarshQMUL 0:ad3cdc525b99 51 void vToString(int v, char* s) {
WilliamMarshQMUL 0:ad3cdc525b99 52 s[3] = '0' + (v % 10) ;
WilliamMarshQMUL 0:ad3cdc525b99 53 v = v / 10 ;
WilliamMarshQMUL 0:ad3cdc525b99 54 s[2] = '0' + (v % 10) ;
WilliamMarshQMUL 0:ad3cdc525b99 55 v = v / 10 ;
WilliamMarshQMUL 0:ad3cdc525b99 56 s[0] = '0' + (v % 10) ;
WilliamMarshQMUL 0:ad3cdc525b99 57 }
WilliamMarshQMUL 0:ad3cdc525b99 58
WilliamMarshQMUL 0:ad3cdc525b99 59 // Main program
WilliamMarshQMUL 0:ad3cdc525b99 60 // Initialise variables
WilliamMarshQMUL 0:ad3cdc525b99 61 // Attach ISR for ticker
WilliamMarshQMUL 0:ad3cdc525b99 62 // Procss messages from mailbox
WilliamMarshQMUL 0:ad3cdc525b99 63 int main() {
WilliamMarshQMUL 0:ad3cdc525b99 64 led1 = 1 ; // turn off
WilliamMarshQMUL 0:ad3cdc525b99 65 int volts = 0 ;
WilliamMarshQMUL 0:ad3cdc525b99 66 const int threshold = 100 ;
WilliamMarshQMUL 0:ad3cdc525b99 67 int counter = 0 ;
WilliamMarshQMUL 0:ad3cdc525b99 68 char vstring[] = "X.XX\r\n" ;
WilliamMarshQMUL 3:f5d7fddeef39 69
WilliamMarshQMUL 3:f5d7fddeef39 70 // start the ADC reading thread
WilliamMarshQMUL 3:f5d7fddeef39 71 ADCthread.start(callback(readA0));
WilliamMarshQMUL 0:ad3cdc525b99 72
WilliamMarshQMUL 0:ad3cdc525b99 73 while (true) {
WilliamMarshQMUL 0:ad3cdc525b99 74 osEvent evt = mailbox.get(); // wait for mail
WilliamMarshQMUL 0:ad3cdc525b99 75 if (evt.status == osEventMail) {
WilliamMarshQMUL 0:ad3cdc525b99 76 message_t* mess = (message_t*)evt.value.p ;
WilliamMarshQMUL 0:ad3cdc525b99 77 volts = (mess->analog * 330) / 0xffff ;
WilliamMarshQMUL 0:ad3cdc525b99 78 mailbox.free(mess) ; // free the message space
WilliamMarshQMUL 0:ad3cdc525b99 79 if (volts > threshold) led1 = 0 ; else led1 = 1 ;
WilliamMarshQMUL 0:ad3cdc525b99 80 vToString(volts, vstring) ;
WilliamMarshQMUL 0:ad3cdc525b99 81 counter++ ;
WilliamMarshQMUL 0:ad3cdc525b99 82 if (counter == 10) { // limit bandwidth of serial
WilliamMarshQMUL 0:ad3cdc525b99 83 pc.printf(vstring) ;
WilliamMarshQMUL 0:ad3cdc525b99 84 counter = 0 ;
WilliamMarshQMUL 0:ad3cdc525b99 85 }
WilliamMarshQMUL 0:ad3cdc525b99 86 }
WilliamMarshQMUL 0:ad3cdc525b99 87
WilliamMarshQMUL 0:ad3cdc525b99 88 }
WilliamMarshQMUL 0:ad3cdc525b99 89 }