Sebastian Barrera / Mbed OS Lab3_ADC

Proposed solution to lab 3

main.cpp@4:ebd00f94455a, 2019-01-31 (annotated)

Committer:
WilliamMarshQMUL
Date:
Thu Jan 31 13:53:15 2019 +0000
Revision:
4:ebd00f94455a
Parent:
3:f5d7fddeef39
Child:
6:a5841dd9e3b2
Replace Ticker with event queue and thread

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 4:ebd00f94455a 4 // Revised to replace Ticker with event queue and thread
WilliamMarshQMUL 0:ad3cdc525b99 5
WilliamMarshQMUL 0:ad3cdc525b99 6 #include "mbed.h"
WilliamMarshQMUL 1:126dd2f5fc2d 7
WilliamMarshQMUL 0:ad3cdc525b99 8
WilliamMarshQMUL 0:ad3cdc525b99 9 AnalogIn ain(A0) ; // Analog input
WilliamMarshQMUL 0:ad3cdc525b99 10 DigitalOut led1(LED_RED); // Red LED
WilliamMarshQMUL 4:ebd00f94455a 11 EventQueue queue; // creates an event queue, to call read ADC
WilliamMarshQMUL 0:ad3cdc525b99 12
WilliamMarshQMUL 0:ad3cdc525b99 13 Serial pc(USBTX, USBRX); // tx, rx, for debugging
WilliamMarshQMUL 0:ad3cdc525b99 14
WilliamMarshQMUL 4:ebd00f94455a 15 // This thread runs the event queue
WilliamMarshQMUL 4:ebd00f94455a 16 Thread eventThread ;
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 4:ebd00f94455a 27 // Average using a low pass filter
WilliamMarshQMUL 0:ad3cdc525b99 28 // Every 10th value is sent to mailbox
WilliamMarshQMUL 4:ebd00f94455a 29 volatile int samples = 0 ;
WilliamMarshQMUL 4:ebd00f94455a 30 volatile uint16_t smoothed = 0 ;
WilliamMarshQMUL 4:ebd00f94455a 31
WilliamMarshQMUL 0:ad3cdc525b99 32 void readA0() {
WilliamMarshQMUL 4:ebd00f94455a 33 smoothed = (smoothed >> 1) + (ain.read_u16() >> 1) ;
WilliamMarshQMUL 4:ebd00f94455a 34 samples++ ;
WilliamMarshQMUL 4:ebd00f94455a 35 if (samples == 10) {
WilliamMarshQMUL 4:ebd00f94455a 36 // send to thread
WilliamMarshQMUL 4:ebd00f94455a 37 message_t *mess = mailbox.alloc() ; // may fail but does not block
WilliamMarshQMUL 4:ebd00f94455a 38 if (mess) {
WilliamMarshQMUL 4:ebd00f94455a 39 mess->analog = smoothed ;
WilliamMarshQMUL 4:ebd00f94455a 40 mailbox.put(mess); // fails but does not block if full
WilliamMarshQMUL 0:ad3cdc525b99 41 }
WilliamMarshQMUL 4:ebd00f94455a 42 samples = 0;
WilliamMarshQMUL 4:ebd00f94455a 43 }
WilliamMarshQMUL 0:ad3cdc525b99 44 }
WilliamMarshQMUL 0:ad3cdc525b99 45
WilliamMarshQMUL 0:ad3cdc525b99 46 // Write voltage digits
WilliamMarshQMUL 0:ad3cdc525b99 47 // v Voltage as scale int, e.g. 3.30 is 330
WilliamMarshQMUL 0:ad3cdc525b99 48 void vToString(int v, char* s) {
WilliamMarshQMUL 0:ad3cdc525b99 49 s[3] = '0' + (v % 10) ;
WilliamMarshQMUL 0:ad3cdc525b99 50 v = v / 10 ;
WilliamMarshQMUL 0:ad3cdc525b99 51 s[2] = '0' + (v % 10) ;
WilliamMarshQMUL 0:ad3cdc525b99 52 v = v / 10 ;
WilliamMarshQMUL 0:ad3cdc525b99 53 s[0] = '0' + (v % 10) ;
WilliamMarshQMUL 0:ad3cdc525b99 54 }
WilliamMarshQMUL 0:ad3cdc525b99 55
WilliamMarshQMUL 0:ad3cdc525b99 56 // Main program
WilliamMarshQMUL 0:ad3cdc525b99 57 // Initialise variables
WilliamMarshQMUL 0:ad3cdc525b99 58 // Attach ISR for ticker
WilliamMarshQMUL 0:ad3cdc525b99 59 // Procss messages from mailbox
WilliamMarshQMUL 0:ad3cdc525b99 60 int main() {
WilliamMarshQMUL 0:ad3cdc525b99 61 led1 = 1 ; // turn off
WilliamMarshQMUL 0:ad3cdc525b99 62 int volts = 0 ;
WilliamMarshQMUL 0:ad3cdc525b99 63 const int threshold = 100 ;
WilliamMarshQMUL 0:ad3cdc525b99 64 int counter = 0 ;
WilliamMarshQMUL 0:ad3cdc525b99 65 char vstring[] = "X.XX\r\n" ;
WilliamMarshQMUL 3:f5d7fddeef39 66
WilliamMarshQMUL 4:ebd00f94455a 67 // Start the event queue
WilliamMarshQMUL 4:ebd00f94455a 68 eventThread.start(callback(&queue, &EventQueue::dispatch_forever));
WilliamMarshQMUL 4:ebd00f94455a 69
WilliamMarshQMUL 4:ebd00f94455a 70 // call the readA0 function every 10ms
WilliamMarshQMUL 4:ebd00f94455a 71 queue.call_every(10, 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 }