Electronic – Atmega168 USART RX Interrupt does not trigger

atmelatmel-studioc

I have been trying to get the USART RX interrupt trigger working on my ATmega168A using the tutorial here (updating my registers as per the datasheet): Tutorials

I have setup the system to use a baud of 4800 at a freq of 1MHz (8Mhz internal oscillator div/8), prescale value of 12 came from the microchip datasheet.

Using the normal serial communications (inside my main loop), the system works as expected and echos the transmitted char back to the pc console. I then added the 2 lines at the end of the function USART_Init() which should enable the RX interrupt and the global interrpt but when typing over the same serial connection which worked, noting happens which suggests to me that either its not triggering or theres an error.

I have searched google and the stack overflow for other instances and I havent been able to find anything which matches my issue or the many links i have found suggest doing things which I already have in my code/tried before.

Have I missed something or have I got a fault in something?

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

#define F_CPU 1000000UL
#define BAUD 4800
#define BAUD_PRESCALE 12


void USART_Transmit( unsigned char data )
{
/* Wait for empty transmit buffer */
while ( !( UCSR0A & (1<<UDRE0)) )
;
/* Put data into buffer, sends the data */
UDR0 = data;
}

unsigned char USART_Receive( void )
{
/* Wait for data to be received */
while ( !(UCSR0A & (1<<RXC0)) )
;
/* Get and return received data from buffer */
return UDR0;
}

void USART_Init( unsigned int ubrr)
{
/*Set baud rate */
UBRR0H = (unsigned char)(ubrr>>8);
UBRR0L = (unsigned char)ubrr;
/* Enable receiver and transmitter */
UCSR0B = (1<<RXEN0)|(1<<TXEN0);
/* Set frame format: 8data, 1stop bit */
UCSR0C = (0<<USBS0)|(1<<UCSZ00)|(1<<UCSZ01);
/*enable RX interrupt */
UCSR0B |= (1 << RXCIE0);
sei();
}

int main(void)
{
USART_Init(BAUD_PRESCALE);
while (1) 
{
    //a = USART_Receive();
    //USART_Transmit(a);
    _delay_ms(100);
}
}

ISR(USART_RX_vect, ISR_BLOCK){
char ReceivedByte ;
ReceivedByte = UDR0 ; // Fetch the received byte value into the variable " ByteReceived "
UDR0 = ReceivedByte ; // Echo back the received byte back to the computer

}

I am using ATmel Studio 7 with WinAvr to code, compile and program the chip.

Best Answer

You need to change ISR(USART_RX_vect, ISR_BLOCK) to ISR(USART0_RX_vect, ISR_BLOCK)

Beware when following code examples online. With the newer chips they started adding numbers to a lot of the registers/macros.

Related Solutions

PIC32 RTCC running too fast 1min = 10 sec

This doesn't answer your question, but might make the code a little easier for you to debug. The case statements are really long and may not be the best way to explain what you are doing with your outputs. I make no guarantees that the code is operational (I have not run it at all), but this should get you thinking about file size and readability.

Your singleminutes case statement has a truth table like this:

//    | out
//  in| 0 1 2 3 4
// ---------------
//  0 | 0 0 0 0 0
//  1 | 0 1 0 0 0
//  2 | 0 1 1 0 0
//  3 | 0 1 1 1 0
//  4 | 0 1 1 1 1

which might be better represented with output-centric code like this:

if (singleminutes >= 1)
    PPEins = 1;
else
    PPEins = 0;

if (singleminutes >= 2)
    PPZwei = 1;
else
    PPZwei = 0;

if (singleminutes >= 3)
    PPDrei = 1;
else
    PPDrei = 0;

if (singleminutes >= 4)
    PPVier = 1;
else
    PPVier = 0;

The nfminutes is a little more complicated, but here is the Truth Table:

//   | MHUhr PMFuenf PMZehn PMViertel PMZwanzig PMVor PMNach PMHalb |        |
// --|--------------------------------------------------------------|--------|-----
// 0 | 1     0       0      0         0         0     0      0      | 1000 0 |  000
// 1 | 0     1       0      0         0         0     1      0      | 0100 0 |  010
// 2 | 0     0       1      0         0         0     1      0      | 0010 0 |  010
// 3 | 0     0       0      1         0         0     1      0      | 0001 0 |  010
// 4 | 0     0       0      0         1         0     1      0      | 0000 1 |  010
// 5 | 0     1       0      0         0         1     0      1      | 0000 0 |  101
// 6 | 0     0       0      0         0         0     0      1      | 0000 0 |  001
// 7 | 0     1       0      0         0         0     1      1      | 0100 0 |  011
// 8 | 0     0       0      0         1         1     0      0      | 0000 1 |  100
// 9 | 0     0       0      1         0         1     0      0      | 0001 0 |  100
//10 | 0     0       1      0         0         1     0      0      | 0010 0 |  100
//11 | 0     1       0      0         0         1     0      0      | 0100 0 |  100

and again some output-centric code:

    // MHUhr PMFuenf PMZehn PMViertel PMZwanzig
if( nfminutes == 0 )
    MHUhr = 1;
else
    MHUhr = 0;

if(( nfminutes == 1 ) || (nfminutes == 5) || (nfminutes == 7) || (nfminutes == 11))
    PMFuenf = 1;
else
    PMFuenf = 0;

if(( nfminutes == 2 ) || (nfminutes == 10) )
    PMZehn = 1;
else
    PMZehn = 0;
if(( nfminutes == 3 ) || (nfminutes == 9) )
    PMViertel = 1;
else
    PMViertel = 0;

if(( nfminutes == 4 ) || (nfminutes == 8) )
    PMZwanzig = 1;
else
    PMZwanzig = 0;


// PMVor PMNach PMHalb
if( ((nfminutes >= 1 ) && (nfminutes <= 4 )) || (nfminutes == 7))
    PMNach = 1;
else
    PMNach = 0;

if( (nfminutes >= 5) && (nfminutes <= 7 )
    PMHalb = 1;
    else
        PMHalb = 0;
if(nfminutes >=8)
    PMVor  = 1;
else
    PMVor  = 0;

The code above might do well with some #defines too

#define UHR     0
#define PHUENF_NACH 1
#define ZEHN_NACH   2
...
if(nfminutes == UHR)

Again for hours. Truth Table:

      | 12  1  2  3  4  5  6  7  8  9 10 11
//----|------------------------------------
// 0  | 1  0  0  0  0  0  0  0  0  0  0  0 
// 1  | 0  1  0  0  0  0  0  0  0  0  0  0 
// 2  | 0  0  1  0  0  0  0  0  0  0  0  0 
// 3  | 0  0  0  1  0  0  0  0  0  0  0  0 
// 4  | 0  0  0  0  1  0  0  0  0  0  0  0 
// 5  | 0  0  0  0  0  1  0  0  0  0  0  0 
// 6  | 0  0  0  0  0  0  1  0  0  0  0  0 
// 7  | 0  0  0  0  0  0  0  1  0  0  0  0 
// 8  | 0  0  0  0  0  0  0  0  1  0  0  0 
// 9  | 0  0  0  0  0  0  0  0  0  1  0  0 
// 10 | 0  0  0  0  0  0  0  0  0  0  1  0 
// 11 | 0  0  0  0  0  0  0  0  0  0  0  1

and code. Slightly different structure with all outputs being cleared, then only the correct output turned on.

// one-hot, clear all will not cause a glitch
PHZwoelf    = 0;
PHEins      = 0;
PHZwei      = 0;
PHDrei      = 0;
PHVier      = 0;
PHFuenf     = 0;
PHSechs     = 0;
PHSieben    = 0;
PHAcht      = 0;
PHNeun      = 0;
PHZehn      = 0;
PHElf       = 0;

if( hours == 0 )
    PHZwoelf = 1;   
if( hours == 1 )
    PHEins = 1;
if( hours == 2 )
    PHZwei = 1; 
if( hours == 3 )
    PHDrei = 1; 
if( hours == 4 )
    PHVier = 1; 
if( hours == 5 )
    PHFuenf = 1;    
if( hours == 6 )
    PHSechs = 1;    
if( hours == 7 )
    PHSieben = 1;   
if( hours == 8 )
    PHAcht = 1; 
if( hours == 9 )
    PHNeun = 1; 
if( hours == 10 )
    PHZehn = 1; 
if( hours == 11 )
    PHElf = 1;

All this also allows you to do your input calculations together before your case statements.

// update single minutes
int singleminutes = (int) (unbcd(tm.min)%5);    // 1, 2, 3, 4
// update 5 minutes
int nfminutes = (int) (unbcd(tm.min)/5);    // Fuenf Nach, Zehn Nach, ...
// update hours
int hours = (int) (unbcd(tm.hour)%12);      // 12, 1, 2, 3, 4...
if(nfminutes>=5) hours++;           // 7:25 = Fuenf Vor Halb Acht (8)

Electronic – PIC18 USART Interrupt for reception, doesn’t trigger

Every processor has its own special interrupt-handling quirks.

Microchip's PIC18F4331 page has links to an errata document and the PIC18F4331 datasheet. In particular, the datasheet has some good tips in section 20 "Enhanced universal synchronous asynchronous receiver transmitter (EUSART)" and even more particularly, the 3 steps listed in section 20.0 and the 10 steps of "To set up an Asynchronous Reception" in section 20.3.2.

I've changed a few things that look like they might help:

// WARNING: untested code
int main(void){

//***********************Initializing Values****************************//
unsigned int ResultADC, FLAG; 
unsigned char temp, idle; //High Byte result store, 8bits long

//***********************ADC and SPI Settings****************************//

Initialize_control();    //Initialize Control Configuration Pins
InitializeADC();         //Initialize ADC in Continuous Mode
USART_initialize();      //Initialize USART module
InitializeMasterSPI();   //Initialize SPI module

//***********************ADC Capture and Output to SPI******************//

  while(1){             //While ADC buffer has something

    //Enable transmission
     TXREG = 0xff; //Debugger

     while(!TXSTAbits.TRMT);//wait while TSR is full

     TXREG = 0x0; //Debugger

     while(!TXSTAbits.TRMT);//wait while TSR is full

  }
  return 0;
}

//////////////////INTERRUPT SERVICE ROUTINE/////////////////

static void interrupt isr(void){
    // The PIC hardware has already disabled global interrupts
    // by the time it starts executing the ISR,
    // so there's no need to do "PIE1bits.RCIE  = 0;".

int count;

//Read USART data
//PIR1bits.RCIF;//Data has been passed to RCREG
RX_Data[count] = RCREG; //Read RX register
count++;
//Reading RCREG automatically clears the RX flag.
// so there's no need to do "PIR1bits.RCIF = 0;".
// Q: How to read more than 1 byte?
// A: FIGURE 20-5 of the datasheet
// Implies that there's only a 1 byte buffer.
// Therefore, to read more than 1 byte, we must:
// pull the current byte out of the hardware buffer,
// store it in a software buffer RX_Data[] in RAM,
// then return to normal background main loop
// until the next byte in the message
// triggers another interrupt.

// Would it be better to do the following in the main loop?
  if (count==3){
    //Use data for control
    Control_Arduino(RX_Data);
    count = 0;
  }

/*
The datasheet p. 229 is a little confusing about
whether "CREN" should be set (step 5) or cleared (step 9).
p. 219 which clearly seems to say CREN should be set.
But maybe it needs to be cleared to flush out any errors,
and then be set?
Are the following 2 lines really necessary?
*/
RCSTAbits.CREN = 0; //clear error (if any)
RCSTAbits.CREN = 1; //Enables Receiver

// the PIC hardware enables global interrupts
// automatically during the return-from-interrupt,
// so there's no need to do a "PIE1bits.RCIE  = 1;"
// See the datasheet section 10.0: "Interrupts" for details.

}

//**********************Functions****************************//

void USART_initialize(void){

//Configuration TX and RX pins
// *normally* we use a "0" to indicate "output",
// but the TX output pin is different, see p. 217 of datasheet
TRISCbits.RC6 = 1; //TX output
TRISCbits.RC7 = 1; //RX input

//TXSTA: Transmit Status and Control Register
TXSTAbits.SYNC = 0; //Asynchronous mode
TXSTAbits.TX9 = 0; //8bit transmission
TXSTAbits.BRGH = 1; //Set HIGH Baud rate
TXSTAbits.TXEN = 1; //Enable transmitter
TXSTAbits.SENDB = 0; //Disable break

//RCSTA: Receive Status and Control Register
RCSTAbits.SPEN = 1; //Serial Port enabled
RCSTAbits.RX9 = 0; //8bit reception
RCSTAbits.CREN = 1; //Enables Receiver

//Test bits
//    RCSTAbits.FERR = 0; //No framing error, cleared by reading
//    RCSTAbits.OERR = 0; //No Overrun error, cleared by clearing CREN
                      //Disable receiver CREN 0

//BAUDCON Control register
BAUDCONbits.BRG16 = 1;  //16bit baud rate generator
SPBRG = 0xCF;           // Set to 19200 baud rate, 12Mhz, High Speed, BRG16
//Test bits
//    BAUDCONbits.RCIDL = 0; //Receive in progress

// USART interrupts configuration
RCONbits.IPEN   = 1; // ENABLE interrupt priority
// (p. 4 of http://www.gooligum.com.au/tutorials/midrange/PIC_Mid_C_3.pdf )
ei(); // same as INTCONbits.GIE  = 1; // ENABLE interrupts
INTCONbits.PEIE = 1; // ENable peripheral interrupts.
PIE1bits.RCIE   = 1; // ENABLE USART receive interrupt
PIE1bits.TXIE   = 0; // disable USART TX interrupt

// make sure the RX flag is clear
    PIR1bits.RCIF = 0;
}

Other code online:

"AN944: Using the EUSART on the PIC16F688" http://www.gooligum.com.au/tutorials/midrange/PIC_Mid_C_3.pdf https://forum.sparkfun.com/viewtopic.php?t=7542 http://panteltje.com/panteltje/pic/scope_pic/ http://www.microchip.com/forums/m411875.aspx http://www.enmcu.com/guides/autobaudratebasedoneusartmodule

Tell us if you ever figure out the real problem, OK?

Best Answer

Related Solutions

PIC32 RTCC running too fast 1min = 10 sec

Electronic – PIC18 USART Interrupt for reception, doesn’t trigger

Related Topic