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Digital to analog conversion. Reads analog signal (voltage) and depending on it, sets the frequency to produce the analog output for sine wave.
Fork of DACandticker_sample by
main.cpp
- Committer:
- natgovor
- Date:
- 2018-02-09
- Revision:
- 3:ac3412621bf9
- Parent:
- 2:e27fd3b65155
File content as of revision 3:ac3412621bf9:
// Lab 3 Example Program 2 // ----------------------- // Periodically write to the AnalogOut to create a sine wave // Alternate between two fixed frequencies every 5 sec // // Updated for mbed 5 // THIS VERSION HAS NO DEBUGGING CODE #include "mbed.h" #include "sineTable.h" Ticker tick ; // Creates periodic interrupt Ticker adcTick ; // Creates periodic interrupt AnalogOut ao(PTE30) ; // Analog output AnalogIn ain(A0) ; // Analog input Serial pc(USBTX, USBRX); // tx, rx, for debugging // Message type typedef struct { uint16_t analog; /* Analog input value */ } message_t; // Mail box Mail<message_t, 2> mailbox; // Function called every 10ms to read ADC // Low pass filter // Every 10th value is sent to mailbox volatile int samples = 0 ; volatile uint16_t smoothed = 0 ; void readA0() { smoothed = (smoothed >> 1) + (ain.read_u16() >> 1) ; samples++ ; if (samples == 10) { // send to thread message_t *mess = mailbox.alloc() ; // may fail but does not block if (mess) { mess->analog = smoothed ; mailbox.put(mess); // fails but does not block if full } samples = 0; } } // Write voltage digits // v Voltage as scale int, e.g. 3.30 is 330 void vToString(int v, char* s) { s[3] = '0' + (v % 10) ; v = v / 10 ; s[2] = '0' + (v % 10) ; v = v / 10 ; s[0] = '0' + (v % 10) ; } // Function called periodically // Write new value to AnalogOut volatile int index = 0 ; // index into array of sin values void writeAout() { ao.write_u16(sine[index]) ; index = (index + 1) % 64 ; } // Control the frequency of updates // Alternative between two frequencies int main() { int volts = 0 ; int counter = 0 ; char vstring[] = "X.XX\r\n" ; int update_us = 1000 ; // 1ms int maximum_voltage = 330; adcTick.attach_us(callback(&readA0), 10000); // ticks every 10ms int f = 0; int old_update_us = update_us; tick.attach_us(callback(&writeAout), update_us); // setup ticker to write to AnalogOut while (true) { osEvent evt = mailbox.get(); // wait for mail if (evt.status == osEventMail) { message_t* mess = (message_t*)evt.value.p ; volts = (mess->analog * 330) / 0xffff ; mailbox.free(mess) ; // free the message space // change the frequency f = 1 + (49 * volts / maximum_voltage); update_us = 1000000 / (f * 64); if (update_us != old_update_us) { tick.attach_us(callback(&writeAout), update_us); // setup ticker to write to AnalogOut old_update_us = update_us; } vToString(volts, vstring) ; counter++ ; if (counter == 10) { // limit bandwidth of serial pc.printf(vstring) ; counter = 0 ; } } Thread::wait(200) ; } }