MicroChip dsPic33, UART RX interrupt is not being called - c

Good afternoon,
I've configured my RX interrupt using the following simple function.
char c;
void __attribute__((interrupt, no_auto_psv)) _U1RXInterrupt( void )
{
IFS0bits.U1RXIF = 0; // Clear RX Interrupt flag
c = U1RXREG;
}
The problem is, UART transmits fine, but the interrupt service routine is never entered when it gets sent a character. I can trace with a scope that the character is actually sent without issues, but the interrupt does not get triggered.
The device used for communication is TTL-232R-3v3. The device is running at 3.3V
The actual model number of the dspic33 is p33FJ128MC802
The programming environment is Mplab 8 and the compiled is XC16
Is there a missing setting to perhaps enable the interrupt? What could be missing?
Thanks,
Here is the UART initialization code.
U1MODEbits.UARTEN = 0; // Bit15 TX, RX DISABLED, ENABLE at end of func
U1MODEbits.USIDL = 0; // Bit13 Continue in Idle
U1MODEbits.IREN = 0; // Bit12 No IR translation
U1MODEbits.RTSMD = 0; // Bit11 Simplex Mode
U1MODEbits.UEN = 0; // Bits8,9 TX,RX enabled, CTS,RTS not
U1MODEbits.WAKE = 0; // Bit7 No Wake up (since we don't sleep here)
U1MODEbits.LPBACK = 0; // Bit6 No Loop Back
U1MODEbits.ABAUD = 0; // Bit5 No Autobaud (would require sending '55')
U1MODEbits.URXINV = 0; // Bit4 IdleState = 1 (for dsPIC)
U1MODEbits.BRGH = 0; // Bit3 16 clocks per bit period
U1MODEbits.PDSEL = 0; // Bits1,2 8bit, No Parity
U1MODEbits.STSEL = 0; // Bit0 One Stop Bit
// U1BRG = (Fcy / (16 * BaudRate)) - 1
// U1BRG = (36850000 / (16 * 9600)) - 1
// U1BRG = 238.908854 //Round to 239
U1BRG = 239;
U1STAbits.UTXISEL1 = 0; //Bit15 Int when Char is transferred (1/2 config!)
U1STAbits.UTXINV = 0; //Bit14 N/A, IRDA config
U1STAbits.UTXISEL0 = 0; //Bit13 Other half of Bit15
U1STAbits.UTXBRK = 0; //Bit11 Disabled
U1STAbits.UTXEN = 0; //Bit10 TX pins controlled by periph
U1STAbits.UTXBF = 0; //Bit9 *Read Only Bit*
U1STAbits.TRMT = 0; //Bit8 *Read Only bit*
U1STAbits.URXISEL = 0; //Bits6,7 Int. on character recieved
U1STAbits.ADDEN = 0; //Bit5 Address Detect Disabled
U1STAbits.RIDLE = 0; //Bit4 *Read Only Bit*
U1STAbits.PERR = 0; //Bit3 *Read Only Bit*
U1STAbits.FERR = 0; //Bit2 *Read Only Bit*
U1STAbits.OERR = 0; //Bit1 *Read Only Bit*
U1STAbits.URXDA = 0; //Bit0 *Read Only Bit*
RPINR18bits.U1RXR = 0b00010;//7; //RX is Pin RP2
RPOR1bits.RP3R = 0b00011; //TX is pin RP3
U1MODEbits.UARTEN = 1; // And turn the peripheral on
U1STAbits.UTXEN = 1;

Check if the pin has additional functionality. Typically this is AD (analog pin). Make sure you turn off all analog, via the ADP or ANSEL registers (type and number varies depending on exact chip) E.g. I have this routine (I use both 33F and 33E and a high and low pincount one of both, hence the ifdefs)
void analogoff(void){
#if defined(__dsPIC33F__)
ADPCFG =0xFFFF;
AD1PCFGH=0xFFFF;
AD1PCFGL=0xFFFF;
#endif
#if defined(__dsPIC33E__)
#if !defined(__dsPIC33EP256MU806__)
ANSELA=0;
#endif
ANSELB=0;
ANSELC=0;
ANSELD=0;
ANSELE=0;
ANSELG=0;
#endif
}
Also, make absolutely sure the oscillator and thus the part's speed is correct, though if TX has the correct baudrate (scope!) that is probably ok.
My uart1 init:
U1BRG = brgval;
U1MODE = 0x8000; // Reset UART to 8-n-1, alt pins, and enable lowspeed (=bit 3)
U1MODEbits.USIDL =0; // disable module when device is idle.
U1MODEbits.IREN =0; // IRDA disable
U1MODEbits.RTSMD =0; // flow control mode (1= simplex mode)
U1MODEbits.UEN =0; // RTS en CTS controlled by PORTlatches
U1MODEbits.WAKE =0; // no wakeup enabled;
U1MODEbits.LPBACK=0; // loopback disabled
U1MODEbits.ABAUD =0; // no autobaud
#if !defined(__PIC24F__)
U1MODEbits.URXINV =0; // RXINV inversion RX. (0= idle = '1')
#endif
U1MODEbits.BRGH =1; // high speed.
U1MODEbits.PDSEL =0; // 8 bit no parity
U1MODEbits.STSEL =0; // 1 stopbit.
U1STA = 0x0440;
U1STAbits.URXISEL0=0;// Reset status register and enable TX & RX.
U1STAbits.URXISEL1=0; // rx interrupt on a char.
_U1RXIF=0; // Clear UART RX Interrupt Flag
_U1RXIE = 1; // Interruption active pour la reception
_U1RXIP=2;
_U1TXIP=2;
_U1TXIF=0;
_U1TXIE=0; // only enabled when actually sending
U1MODEbits.UARTEN=1;

Related

PIC32 UART: U1RXREG Register Never Contains Any Values Other Than 0

I've attached an image showing my oscilloscope readout which is from the code below. Context: I have a Pi and a PIC which need to communicate through UART connection. I've implemented my own flow control which can be seen in the image attached [RTS = Yellow Trace, CTS = Blue Trace, Rx = Green Trace]. The code runs through and is caught in the final switch case statement which turns on an LED. But when i debug the code, no values (well the only value which is read is zero) are read in. At first i thought that i'd configured my PIC clock wrong (which is used to derive the baud rate), but i don't think this is the case. Second i through the FIFO buffer was full of zeros only and considering that i'm sending only four packets of information to the PIC, and my FIFO is 4 registers deep that this was the reason why non of the information was appearing. So i executed a code which removes the dummy bytes but this did not work.
All that is received:
0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0><0> etc
I got the right settings selected: baud rate: 9600 data bits: 8 parity: none stop bits: 1
If anyone is willing to spend some time looking at my code, can you see any obvious errors?
https://i.stack.imgur.com/aQoAL.jpg
Minimum Reproducible Example
# include <xc.h>
# include <math.h>
# include <stdio.h>
# include <stdio.h>
//Configuration Bits
#pragma config FNOSC = FRCPLL // Internal Fast RC Oscillator (8MHz)
#pragma config FPLLIDIV = DIV_2 // Divide FRC before PLL (Now 4MHz)
#pragma config FPLLMUL = MUL_20 // PLL Multiply (Now 80MHz)
#pragma config FPLLODIV = DIV_2 // Divide After PLL (Now 40MHz)
#pragma config FPBDIV = DIV_1 // Pheripheral Bus Clock (At 40KHz)
#pragma config FWDTEN = OFF // Watchdog Timer Disabled
#pragma config ICESEL = ICS_PGx2 // ICE/ICD Comm Channel Select
#pragma config JTAGEN = OFF // Disable JTAG
#pragma config FSOSCEN = OFF // Disable Secondary Oscillator
//*****************************UART Functions***********************************
void UART_Config (void) // Baude Rate of 9600, 8-Bit Data , 1 Stop Bit
{
U1MODEbits.BRGH = 0;
U1BRG = 259; //U1BRG = (40M/ (16 * 9.6k))) - 1
U1MODEbits.SIDL = 0; // Continue operation in SLEEP mode
U1MODEbits.IREN = 0; // IrDA is disabled
U1MODEbits.RTSMD = 0; // U1RTS pin is in Flow Control mode
U1MODEbits.UEN = 0b00; // U1TX, U1RX are enabled
U1MODEbits.WAKE = 1; // Wake-up enabled
U1MODEbits.LPBACK = 0; // Loopback mode is disabled
U1MODEbits.RXINV = 0; // U1RX IDLE state is '1'
U1MODEbits.PDSEL = 0b00; // 8-bit data, no parity
U1MODEbits.STSEL = 0; // 1 stop bit
U1STAbits.UTXINV = 0; // U1TX IDLE state is '1'
U1MODEbits.ON = 1; // UART1 is enabled
U1STAbits.URXEN = 1; // UART1 receiver is enabled
U1STAbits.UTXEN = 1; // UART1 transmitter is enabled
}
void Send_UART_Data(unsigned int c) // PIC Sending Data for Pi to Read
{
U1STAbits.UTXEN = 1; // Make sure transmitter is enabled
// while(CTS) // Optional CTS (Clear to Send) use
while(U1STAbits.UTXBF); // Wait while buffer is full
U1TXREG = c; // Transmit character
}
int Read_UART_Data (void) // PIC Reading Sent Data from Pi
{
int c;
while(!U1STAbits.URXDA) // Wait for information to be received
c = (int)U1RXREG; // Convert Character to Value
return c;
}
ADC_To_UART (unsigned int ADC)
{
unsigned int temp_A = 0x00;
unsigned int temp_B = 0x00;
// Splitting a 10 Bit Word Into 2 Bytes [aa aaaa aabb]
// Start Bit = 1 , Stop Bit = 0
// UART Transmission Pattern [1 aaaa aaaa 0 0000 00 bb]
temp_A = ADC >> 2; // MSB(8 Bits) ~ ADC[9:2] [aaaa aaaa]
temp_B = ADC & 0x003; // LSB(2 Bits) ~ ADC[1:0] [0000 00bb]
Send_UART_Data(temp_A);
Send_UART_Data(temp_B);
}
[enter image description here][1]
//*********************Enumerated Variable Declaration**************************
//Program Flow Control
enum Comm_State {Phase1A, Phase1B, Phase1C, Phase1D, Phase1E, Phase2A, Phase2B, Phase2C, Phase2D, Phase2E, Phase2F, Phase2G};
//******************************************************************************
//********************************MAIN******************************************
int main( )
{
//***************************Configuration**********************************
// I/O Definitions
#define UART_TRIS_RX TRISBbits.TRISB13 // UART RX - Reciever Pin (PPS)
#define UART_TRIS_TX TRISBbits.TRISB15 // UART TX - Transmission Pin (PPS)
#define UART_TRIS_CTS_PIC TRISAbits.TRISA4 // UART CTS_1 - Clear to Send - Output [CTS PIC]
#define UART_TRIS_RTS_PIC TRISBbits.TRISB4 // UART RTS_1 - Ready to Send - Output [RTS PIC]
#define UART_TRIS_CTS_PI TRISAbits.TRISA3 // UART CTS_2 - Clear to Send - Input [CTS PI]
#define UART_TRIS_RTS_PI TRISAbits.TRISA2 // UART_RTS_2 - Ready to Send - Input [RTS PI]
#define SPI_TRIS_SCK TRISBbits.TRISB14 // SPI SCK - Serial Clock Pin (PPS?)
#define SPI_TRIS_SDO TRISBbits.TRISB6 // SPI SDO - Serial Data Out Pin (PPS?)
#define SPI_TRIS_CS_1 TRISBbits.TRISB8 // SPI CS1 - DAC 2 Chip Select Pin (PPS?)
#define SPI_TRIS_CS_2 TRISBbits.TRISB7 // SPI CS2 - DAC 1 Chip Select Pin (PPS?)
#define AN4_TRIS TRISBbits.TRISB2 // Analogue Read 3
#define AN3_TRIS TRISBbits.TRISB1 // Analogue Read 2
#define AN2_TRIS TRISBbits.TRISB0 // Analogue Read 1
#define V_REF_TRIS_Plus TRISAbits.TRISA0 // Analogue V_REF(+) (Forms VRange)
#define V_REF_TRIS_Minus TRISAbits.TRISA1 // Analogue V_REF(-) (Forms VRange)
#define Reg_Enable_TRIS_D TRISBbits.TRISB9 // Regulator Digital Control (Output)
#define Reg_Enable_TRIS_M TRISBbits.TRISB12 // Regulator Button (Input)
// Port Input/Output Configuration [TRISB]
TRISB = 0x1004; // All of PortB set as Outputs Except for RB12 (Reg Enable) and RB2 (Input -> Analogue Input (Voltage)) (Port B) = (0000 ... 0100)
TRISA = 0x0003; // Set up A0 [Pin 2] and A1 [Pin 3] as V_REF(+) and V_REF(-) Respectively (Port B) = (0000 ... 0011)
UART_TRIS_RX = 1; // UART Receiver ~ Input
UART_TRIS_TX = 0; // UART Transmission ~ Output
UART_TRIS_CTS_PIC = 0; // UART "CTS_PIC" ~ Output
UART_TRIS_RTS_PIC = 0; // UART "RTS_PIC" ~ Output
UART_TRIS_CTS_PI = 1; // UART "CTS_PI" ~ Input
UART_TRIS_RTS_PI = 1; // UART "RTS_PI" ~ Input
SPI_TRIS_SCK = 0; // SPI Clock ~ Output
SPI_TRIS_SDO = 0; // SPI Data Output ~ Output
SPI_TRIS_CS_1 = 0; // SPI Chip Select 1 ~ Output
SPI_TRIS_CS_2 = 0; // SPI Chip Select 2 ~ Output
AN4_TRIS = 1; // Analogue Read In ~ Input
AN3_TRIS = 1; // Analogue Read In ~ Input
AN2_TRIS = 1; // Analogue Read In ~ Input
V_REF_TRIS_Plus = 1; // V_Ref(+) ~ Input
V_REF_TRIS_Minus = 1; // V_Ref(-) Differential Measurements ~ Input
Reg_Enable_TRIS_D = 0; // Regulator Digital Control (Output)
Reg_Enable_TRIS_M = 1; // Regulator Switch Control (Input)
// Peripheral Pin Select Configurations
U1RXR = 0x0011; // UART PPS Mapping
RPB15R = 0x0001; // UART PPS Mapping
// Analogue Pin Configurations
ANSELB = 0x0028; // RB0 RB1 RB2 = AN2 AN3 AN4 [0001 1100]
ANSELA = 0x0000; // Set all Analogue Inputs of Port A Off
//**************Sub-System Configurations*********************************//
// UART Control Configure
UART_Config(); //UART Control Configure
#define PIC_CTS LATAbits.LATA4 // Output Set Definition [1]
#define PIC_RTS LATBbits.LATB4 // Output Set Definition [2]
#define PI_CTS PORTAbits.RA3 // Input Read Definition [2]
#define PI_RTS PORTAbits.RA2 // Input Read Definition [1]
// Analogue Control Configure
ADC_Config(); // Configure ADC
AD1CON1SET = 0x8000; // Enable ADC
//***************Variable Declarations************************************//
enum Comm_State Communication_State = Phase1A; //Controller Variable
unsigned int temp1 = 0;
unsigned int Comms_Flag_1 = 0;
unsigned int ConFlag = 1;
unsigned int i = 1;
unsigned int UART_ADC_CV_1 = 0;
unsigned int UART_ADC_CV_2 = 0;
unsigned int ADC_CV = 0;
unsigned int UART_ADC_CC_1 = 0;
unsigned int UART_ADC_CC_2 = 0;
unsigned int ADC_CC = 0;
unsigned int DAC_CV = 0;
float I_CC = 0;
float V_CV = 0;
//***************Program Flow - Switch State Controlled*******************//
while(1)
{
switch (Communication_State)
{
case Phase1A: // Check For Pi Ready to Send CV ADC Value
//PIC_CTS = 0;
//Pic_Refresh();
PIC_RTS = 0;
PIC_CTS = 1;
if (PI_RTS == 1)
{
PIC_CTS = 0;
Communication_State = Phase1B;
}
break;
case Phase1B: // Receive CV ~ 12 Bit ADC Value [Two Data Packets with 0.01 Second Delay]
ConFlag = 1;
i = 1;
while (ConFlag == 1)
{
if (PI_RTS == 1 && i == 1)
{
UART_ADC_CV_1 = Read_UART_Data(); //Data Packet 1 Returned - MSB(Bit 15) to Bit 8
i++;
}
else if (PI_RTS == 1 && i == 2)
{
UART_ADC_CV_2 = Read_UART_Data(); //Data Packet 2 Returned - Bit (7)) to LSB(Bit 0)
}
else
{
ConFlag = 0;
}
}
Communication_State = Phase1C;
break;
case Phase1C: // Check for CC Value
delay(); //Ensure that Pi_RTS has gone low after sending last Transmission (Prevents Code from Running Away)
PIC_CTS = 1;
if (PI_RTS == 1)
{
PIC_CTS = 0;
Communication_State = Phase1D;
}
break;
case Phase1D: // Receive CC Value [Two Data Packets with 0.01 Second Delay]
ConFlag = 1;
i = 1;
while (ConFlag == 1)
{
if (PI_RTS == 1 && i == 1)
{
UART_ADC_CC_1 = Read_UART_Data(); //Data Packet 1 Returned - MSB(Bit 15) to Bit 8
i++;
}
else if (PI_RTS == 1 && i == 2)
{
UART_ADC_CC_2 = Read_UART_Data(); //Data Packet 2 Returned - Bit (7)) to LSB(Bit 0)
}
else
{
ConFlag = 0;
}
}
Communication_State = Phase1E;
break;
case Phase1E: // Calculations
// CV Calculations
temp1 = UART_ADC_CV_1 << 8;
ADC_CV = temp1 + UART_ADC_CV_2;
V_CV = ADC_CV * (4.096/4096);
DAC_CV = ADC_CV | 4096;
Comms_Flag_1 = SPI_Transfer(DAC_CV ,1); // Data Transmitted to DAC 1, Upon Transmission LED Turns Green (No Acknowledgement)
// CC Calculations
temp1 = UART_ADC_CC_1 << 8;
ADC_CC = temp1 + UART_ADC_CC_2;
I_CC = ADC_CC * (4.096/4096);
Communication_State = Phase2A;
break;
case Phase2A:
while(1)
{
LATBbits.LATB5 = 1;
}
break;
}
}
return 1;
}
In Read_UART_Data, you have:
while(!U1STAbits.URXDA)
c = (int)U1RXREG;
I think you're missing a semicolon because this is actually:
while (!U1STAbits.URXDA)
c = (int) U1RXREG;
This means that c is set only when the UART receiver is not ready.
What I think you meant is:
while (!U1STAbits.URXDA);
c = (int) U1RXREG;

PIC16F1829 UART RX Interrupt not working using MPLABX and XC8 compiler

I am new to writing firmware for 8-bit PICs and could use some help with my code. I am using a PIC16F1829 for an LED module which gets RX commands. I am just trying to get the basics setup like turn on LEDs when a certain value is received on RX pin, but can't even get that.
Would like to get UART working via interrupts but can't even get it working with polling in main loop. My interrupt vector is commented out in the code below.
RX pin: RC5
TX pin: RB7
Pin to toggle LEDs on and off: RA5
Pin RA5 works fine to toggle LEDs on and off. TX pin is working, though I have not confirmed if interrupt TXIF is also not working like RCIF is not working.
I have tried reading RCIF and PIR1bits.RCIF. Both of them compiled. Neither one worked. I have tried this on two different PICs on 2 different LED modules. They turn on, but reading RX pin didn't work on either.
Variable RXIN is initially defined as 3 and thus due to the RXIN-- loop within the main loop the lights flash 3 times at startup so I know it is entering the main loop. But as far as I can tell the RCIF interrupt is not firing upon reception at RX pin.
I have confirmed on oscilloscope that the signal into RX and out of TX pins using same baud, so I think baud rate is configured correctly (300 baud, 8N1.) I have also confirmed on oscilloscope RX pin receiving strong and clean 5V signal. Neither polling RCIF or using an interrupt service routing has worked thus far. If anyone can see the issues with my code that I am not seeing, your help would be greatly appreciated.
My code:
#include <stdio.h>
#include <stdlib.h>
#include <xc.h>
// This is for 300 baud rate
#define _BAUD_PRESCALER_LOW_ 0x2A
#define _BAUD_PRESCALER_HIGH_ 0x68
#define _XTAL_FREQ 32000000
#pragma config FOSC = INTOSC // Oscillator Selection->INTOSC oscillator: I/O function on CLKIN pin
#pragma config WDTE = OFF // Watchdog Timer Enable->WDT enabled
#pragma config PWRTE = OFF // Power-up Timer Enable->PWRT disabled
#pragma config MCLRE = OFF // MCLR Pin Function Select->MCLR/VPP pin function is digital input
#pragma config CP = OFF // Flash Program Memory Code Protection->Program memory code protection is disabled
#pragma config CPD = OFF // Data Memory Code Protection->Data memory code protection is disabled
#pragma config BOREN = ON // Brown-out Reset Enable->Brown-out Reset enabled
#pragma config CLKOUTEN = OFF // Clock Out Enable->CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin
#pragma config IESO = OFF // Internal/External Switchover->Internal/External Switchover mode is disabled
#pragma config FCMEN = OFF // Fail-Safe Clock Monitor Enable->Fail-Safe Clock Monitor is disabled
// CONFIG2
#pragma config WRT = OFF // Flash Memory Self-Write Protection->Write protection off
#pragma config PLLEN = ON // PLL Enable->4x PLL enabled
#pragma config STVREN = ON // Stack Overflow/Underflow Reset Enable->Stack Overflow or Underflow will cause a Reset
#pragma config BORV = LO // Brown-out Reset Voltage Selection->Brown-out Reset Voltage (Vbor), low trip point selected.
#pragma config LVP = OFF
int flagRXFramingError = 0;
int flagRXOverrunError = 0;
volatile unsigned char RXIN = 3;
unsigned char UARTRead(){
return RCREG;
}
void writeRXIN(unsigned char a){
RXIN = a;
}
void TX(unsigned char a){
while(!TXIF){}
TXREG = a;
}
int main(int argc, char** argv) {
// SCS FOSC; SPLLEN disabled; IRCF 8MHz_HF;
OSCCON = 0xF0;
// TUN 0;
OSCTUNE = 0x00;
// Set the secondary oscillator
// Wait for PLL to stabilize
while(PLLR == 0)
{
}
// WDTPS 1:65536; SWDTEN OFF;
WDTCON = 0x16;
__delay_ms(5);
GIE = 1; // Global interrupts enabled
__delay_ms(5);
PEIE = 1; // Active peripheral interrupts enabled
__delay_ms(5);
RCIE = 1; // Enable USART Receive interrupt
__delay_ms(5);
TXIE = 1; // Enable USART Transmitter interrupt
__delay_ms(5);
ADIE = 1; // Enable ADC interrupts
__delay_ms(5);
RXDTSEL = 0; // RX is on RC5 pin
__delay_ms(5);
TXCKSEL = 0; // TX is on RB7 pin
__delay_ms(5);
TRISC5 = 1; // RX pin set as input
__delay_ms(5);
SPEN = 1; // Serial Port Enabled
__delay_ms(5);
SYNC = 0; // Asynchronous mode
__delay_ms(5);
RX9 = 0; // 8 bit reception
__delay_ms(5);
TX9 = 0; // 8-bit transmission
__delay_ms(5);
CREN = 1; // Receiver enabled
__delay_ms(5);
TXEN = 1; // Transmitter enabled
__delay_ms(5);
BRG16 = 1; // 16-bit baud generation
__delay_ms(5);
BRGH = 1; // High baud rate enabled
__delay_ms(5);
ABDEN = 0; // Auto baud detect disabled
__delay_ms(5);
// Baud prescaler n = [Fosc/(D*BR)] - 1
SPBRGH = _BAUD_PRESCALER_HIGH_;
__delay_ms(5);
SPBRGL = _BAUD_PRESCALER_LOW_;
__delay_ms(5);
TRISC6 = 0; // IadjPWM pin configured as output
__delay_ms(5);
ANSC6 = 0; // IadjPWM pin not analog input
__delay_ms(5);
TRISA5 = 0; // DimPWM pin configured as output
__delay_ms(5);
LATC6 = 1; // Max current for now until PWM written
__delay_ms(5);
while(1){
// Inline assembly code to clear watchdog timer
//asm("CLRWDT");
/*if(RXIN == 5){
RA5 = 1;
}
else{
RA5 = 0;
}*/
if(PIR1bits.RCIF){
writeRXIN(UARTRead());
//RA5 = 0;
TX(RXIN);
} // end if RCIF
while(RXIN > 0){
RA5 = 1;
__delay_ms(100);
RA5 = 0;
__delay_ms(100);
RXIN--;
}
}
// infinite loop
// never leave this loop
RA5 = 1;
return (EXIT_SUCCESS);
} // end main
/*void interrupt ISR(void){
if(RCIF){// if USART Receive interrupt flag
RA5 = 1;
if(FERR){
flagRXFramingError = 1;
SPEN = 0;
SPEN = 1;
}
if(OERR){
flagRXOverrunError = 1;
CREN = 0;
CREN = 1;
}
while(RCIF){ // RCIF high as long as there is data in FIFO register. Read RCREG to clear RCIF flag
writeRXIN(UARTRead());
}
RA5 = 0;
}
if (TXIF){// if USART Transmit interrupt
TXIF = 0; // Clear interrupt flag
}
} // end ISRs*/
Some microcontrollers stop receiving bytes if there was some kind of error. Be sure to clear those errors. Usually by clearing some UART control register bits.
SOLVED THE PROBLEM
I am not sure what exactly solved the problem but I will share the major changes I made and the new code.
I had TXIE enabled. TXIF is almost always high, so it generates
continuous interrupts. I don't see a reason to enable TX interrupts,
though there may be a good one. If you want to TX wait until TXIF is
not zero and transmit, otherwise why use the flag?
I had the interrupts enabling in the wrong order. I should have
enabled the peripherals, then their individual interrupts if
necessary, then PEIE, and finally GIE.
I wasn't handling FERR and OERR in my interrupt, though they may
be firing and causing interrupts.
Also I had RXDTSEL set wrong in my original code. Here is the new, working code. Right now all it does is echo the RX signal and blink the LEDs the number of times that is transmitted.
#include <stdio.h>
#include <stdlib.h>
#include <xc.h>
// This is for 300 baud rate
#define _BAUD_PRESCALER_LOW_ 0x2A
#define _BAUD_PRESCALER_HIGH_ 0x68
#define _XTAL_FREQ 32000000
#define _PIN_DIMPWMPIN_ RA5
#pragma config FOSC = INTOSC // Oscillator Selection->INTOSC oscillator: I/O function on CLKIN pin
#pragma config WDTE = OFF // Watchdog Timer Enable->WDT enabled
#pragma config PWRTE = OFF // Power-up Timer Enable->PWRT disabled
#pragma config MCLRE = OFF // MCLR Pin Function Select->MCLR/VPP pin function is digital input
#pragma config CP = OFF // Flash Program Memory Code Protection->Program memory code protection is disabled
#pragma config CPD = OFF // Data Memory Code Protection->Data memory code protection is disabled
#pragma config BOREN = ON // Brown-out Reset Enable->Brown-out Reset enabled
#pragma config CLKOUTEN = OFF // Clock Out Enable->CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin
#pragma config IESO = OFF // Internal/External Switchover->Internal/External Switchover mode is disabled
#pragma config FCMEN = OFF // Fail-Safe Clock Monitor Enable->Fail-Safe Clock Monitor is disabled
// CONFIG2
#pragma config WRT = OFF // Flash Memory Self-Write Protection->Write protection off
#pragma config PLLEN = ON // PLL Enable->4x PLL enabled
#pragma config STVREN = ON // Stack Overflow/Underflow Reset Enable->Stack Overflow or Underflow will cause a Reset
#pragma config BORV = LO // Brown-out Reset Voltage Selection->Brown-out Reset Voltage (Vbor), low trip point selected.
#pragma config LVP = OFF
int flagRXFramingError = 0;
int flagRXOverrunError = 0;
volatile unsigned char RXIN = 3;
unsigned char RX(){
return RCREG;
}
void writeRXIN(volatile unsigned char a){
RXIN = a;
}
void TX(unsigned char a){
while(!PIR1bits.TXIF); // TXIF is usually 1, only 0 when busy transmitting
TXREG = a;
}
int main(int argc, char** argv) {
// SCS FOSC; SPLLEN disabled; IRCF 8MHz_HF;
OSCCON = 0xF0;
// TUN 0;
OSCTUNE = 0x00;
// Set the secondary oscillator
// Wait for PLL to stabilize
while(OSCSTATbits.PLLR == 0){}
ADCON0bits.ADON = 0;
ANSELA = 0x00;
ANSELB = 0x00;
ANSELC = 0x00;
PIE1bits.ADIE = 0; // Disable ADC interrupts
TRISCbits.TRISC5 = 1; // RX pin set to input
TRISCbits.TRISC6 = 0; // IadjPWM pin configured as output
TRISAbits.TRISA5 = 0; // DimPWM pin configured as output
LATCbits.LATC6 = 1; // Max current for now until PWM written
//UART Init
BAUDCONbits.BRG16 = 1; // 16-bit baud generation
TXSTAbits.BRGH = 1; // High baud rate enabled
BAUDCONbits.ABDEN = 0; // Auto baud detect disabled
// Baud prescaler n = [Fosc/(D*BR)] - 1
SPBRGH = _BAUD_PRESCALER_HIGH_;
__delay_ms(1);
SPBRGL = _BAUD_PRESCALER_LOW_;
__delay_ms(1);
APFCON0bits.RXDTSEL = 1; // RX is on RC5 pin
APFCON0bits.TXCKSEL = 0; // TX is on RB7 pin
TXSTAbits.SYNC = 0; // Asynchronous mode
RCSTAbits.SPEN = 1; // Serial Port Enabled
RCSTAbits.RX9 = 0; // 8 bit reception
TXSTAbits.TX9 = 0; // 8-bit transmission
RCSTAbits.CREN = 1; // Receiver enabled
TXSTAbits.TXEN = 1; // Transmitter enabled
PIE1bits.TXIE = 0; // Enable USART Transmitter interrupt
PIE1bits.RCIE = 1; // Enable USART Receive interrupt
while(PIR1bits.RCIF){
writeRXIN(RX());
}
INTCONbits.PEIE = 1; // Enable peripheral interrupts
INTCONbits.GIE = 1; // Enable global interrupts
while(1){
while(RXIN > 0){
TX(RXIN);
_PIN_DIMPWMPIN_ = 1;
__delay_ms(100);
_PIN_DIMPWMPIN_ = 0;
__delay_ms(100);
RXIN--;
}
}
// infinite loop
// never leave this loop
return (EXIT_SUCCESS);
} // end main
void interrupt ISR(void){
if(PIE1bits.RCIE && PIR1bits.RCIF){ // handle RX pin interrupts
while(PIR1bits.RCIF){
writeRXIN(RX());
}
if(RCSTAbits.FERR){
flagRXFramingError = 1;
SPEN = 0;
SPEN = 1;
}
if(RCSTAbits.OERR){
flagRXOverrunError = 1;
CREN = 0;
CREN = 1;
}
} // end RX pin interrupt handlers
} // end ISRs*/

Transmitting 10bit data through The UART of PIC16F877A

I'm beginner to micro controller technology. I want to transmit the 10-bit output I got from an Analog to Digital Conversion, but only 8 bits can be sent via the UART. How can I send 10 bits?
Please help me to write C code to solve this problem. My code so far is given below. The compiler used is XC8.
#pragma config PWRTE = OFF // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF // Flash Program Memory Code Protection bit (Code protection off)
#define _XTAL_FREQ 4000000
#include <stdio.h>
#include <stdlib.h>
#include <htc.h>
void uart_init(void);
void TX(unsigned char TX_BYTE);
void configure_pins();
unsigned char read_input(unsigned char channel);
void main()
{
__delay_ms(2);
while (1) {
TRISB = 0; //configuring portB as output
TRISC = 0;
TRISA = 1;
configure_pins(); //calling methods
unsigned char x = read_input(0);
uart_initialize();
assign_data_to_tx_pin(x);
}
}
void configure_pins(){
ADCON1 = 0b10000000; //The result is right justified
}
unsigned char read_input(unsigned char channel){ // converting the Analog input to digital
ADCON0=0b00000000;
CHS0=0; // AN0 is selected
CHS1=0; // "
CHS2=0; // "
ADON = 1;
GO_DONE = 1;
while (GO_DONE);
ADON = 0;
return ((ADRESH >> 2) + ADRESL); // return the result of conversion
}
void uart_initialize(void) // initializing the UART for data transmission
{
TRISC = 0; //configuring portC as output
TXSTA = 0b100000000;
TXEN = 1; //enable transmission mode
SPEN = 1; //enable UART
BRGH = 0; //enable low baud
SPBRG = 6; //set baud rate as 9600
SYNC = 0; //enable asynchronous transmission
RCIE = 1;
GIE = 1;
PEIE = 1;
}
void assign_data_to_tx_pin(unsigned char converted_data) { // assigning the data to the Tx pin for transmission
while(!TRMT) {
unsigned char a = converted_data;
TXREG = a;
TXREG = a >> 2;
PORTCbits.RC6 = TXREG;
__delay_ms(100); // Delay
}
}
Typical UARTs do not allow for more than 8 bits of data per transmission. Some allow 9. Sending 10 bits may be available on select UARTS using 9 bits and controlling the parity, but that is rare.
Instead recommend to send the data as 2 transmission with a bit set aside to denote which half is sent.
Send_ADC(void){
ADCON0=0b00000000;
CHS0=0; // AN0 is selected
CHS1=0; // "
CHS2=0; // "
ADON = 1;
GO_DONE = 1;
while (GO_DONE);
ADON = 0;
unsigned adc10 = ((ADRESH >> 2) + ADRESL);
assign_data_to_tx_pin((adc10 % 32) * 2 + 0); // 00lllll0
assign_data_to_tx_pin((adc10 / 32) * 2 + 1); // 00hhhhh1
}
On receiver side, insure bytes received are in the proper byte order. This will re-construct the received data in the proper order, even if reception does not start in phase or if a byte was lost in communication.
// return 0: success, else 1
int ReadSerialADC(unsigned *data) {
unsigned adc;
unsigned low = read_from_comport();
if (low %2) return 1;
low /= 2;
unsigned high = read_from_comport();
if (high %2 == 0) return 1;
high /= 2;
*data = high * 32 + low;
return 0;
}
You are reading a 10-bit ADC result with like this
return ((ADRESH>>2)+ADRESL);
But the function is return unsigned char, it should be unsigned int
unsigned int read_input(unsigned char channel)
and the calling function is also throwing away two bits with
unsigned char x=read_input(0);
which should be
unsigned int x=read_input(0);
Having read a 10-bit value into a (presumably) 16-bit variable, you now have to transmit it to the serial port. Let's do this by sending the most significant 8 bits first.
TX (x >> 8);
TX (x & 0xFF);
Then at the receiver end you read the two bytes and put them back together
unsigned adcval = RX() << 8;
adcval |= RX();

No response from UART

I'm able to receive with the following code, but unfortunately, nothing is sent back. What am I doing wrong?
#include <pic18f25k80.h>
#include "config.h"
#include <usart.h>
int i = 0;
unsigned char MessageBuffer[200];
void main() {
OSCCONbits.IRCF = 0b110; // 8MHz
TRISB6 = 0; // TX set as output
TRISB7 = 0; // RX set as output
// Clear TX interrupt
// Set RX interrupt
// 8-bit Asynch. mode
// BRGH = 1 = high baud mode
// 51 = ((8MHz/baud)/16)-1 with baud = 9600
Open2USART(USART_TX_INT_OFF & USART_RX_INT_ON & USART_ASYNCH_MODE
& USART_EIGHT_BIT & USART_BRGH_HIGH, 51 );
RC2IF = 0; // reset RX2 flag
RC2IP = 0; // not high priority
RC2IE = 1; // Eneble RX2 interrupt
INTCONbits.PEIE = 1; // enable peripheral interrupts
INTCONbits.GIE = 1; // enable interrupts
RCSTA2bits.SPEN = 1; // enable USART
while(1){
}
}
void interrupt ISR () {
if(PIR3bits.RC2IF == 1) {
if(i<200) { // buffer size
MessageBuffer[i] = Read2USART(); // read byte from RX reg
if (MessageBuffer[i] == 0x0D) { // check for return key
puts2USART(MessageBuffer);
for(;i>0;i--)
MessageBuffer[i] = 0x00; // clear array
i=0;
return;
}
i++;
RC2IF = 0; // clear RX flag
} else {
puts2USART(MessageBuffer);
for(;i>0;i--)
MessageBuffer[i] = 0x00; // clear array
i = 0;
return;
}
}
}
I'm transmitting the 0x41 hex code, I checked with the scope and see that is is being received. And according to the code I have, an echo of the received data should be sent back. When I check the TX pin, nothing is happening.
Add USART_CONT_RX to Open2USART to enable continuous receive.
Also, it's a good idea to do the minimum necessary in the interrupt service routine. Consider something like:
void interrupt ISR () {
char data;
if(PIR3bits.RC2IF == 1) {
data = Read2USART(); // always read byte from RX reg (clears RC2IF)
if(i<200) { // buffer size
MessageBuffer[i] = data; // read byte from RX reg
i++;
}
else{
// flag buffer full error
}
}
}
and doing the rest of what you are doing in the while(1) loop.

Interrupt handling with 8051 C using Keil uVision

I've been doing a project about home automation in which I have to use timer interrupts with 8051 microcontroller. I've constructed the following code, however I couldn't manage to get interrupt working. It seems that the program does not go into timer ISR at all. I use a buton to simulate PIR input, therefore lampControl is triggered, no worries there. I use as a library.
Any ideas or help will be greately appreciated:
void timer0_isr(void) interrupt 1 //Timer 0 Interrupt
{
TH0 = 0xDC;
TL0 = 0x00;
TR0 = 1;
if (++lamp_interrupt_count == 6000)
{
sendCharacterShowAsHex(0x8F);
lamp_interrupt_count = 0;
TR0 = 0;
}
}
void main()
{
unsigned char chr;
IE = 0x93;
while(1)
{
serialInput();
if (getPIRInput() == 0x00)
{
lampControl(0x80);
}
....
....
....
}
void lampControl(unsigned char serial_data_in)
{
if (serial_data_in == 0x80)
{
sendCharacterShowAsHex(0x80);
//enable interrupts
IE = 0x93;
device_interrupt = 2; //Lamp
TMOD = 0x21; // Timer0 Gate=0, Mode 1, 16bit timer
TH0 = 0xDC;
TL0 = 0x00;
TR0 = 1;
}
else if(serial_data_in == 0x8F)
{
sendCharacterShowAsHex(0x8F);
}
}
You need to configure the timer and interrupts before you can use them.
In main() you need at least the following configuration bits set in order to be able to turn
the timer on with "TR0 = 1;" :
Set those bits first thing in main() and this should do the trick:
TMOD = 0x01; // 16-bit no auto reload
TH0 = 0xDC; //Set high and low bits to count 0xFFFF - 0xDC00 = 0x23FF counts
TL0 = 0x00;
ET0 = 1; // Enable timer0 interrupt
EA = 1; // Enable all interrupts
//TR0 = 1; //Enable Timer0 immediately
The rest of your code should run fine.
Note: you could change your interrupt function definition to:
"void timer0_isr(void) interrupt 1 using 1" to force it to use register bank 1 for the interrupt function operation.

Resources