I am working with the explorer16/32 evb and trying to send data to UART.
I tried UART1, UART2 with and without interrupts and got the same problem all the time.
It appeared that in order to send 1 byte I need to split it to two 4 bits with shift
code:
#define FCY 16000000
#define BAUDRATE 9600
#define BRGVAL ((FCY/BAUDRATE)/16)-1
U2MODE = 0;
U2STA = 0;
U2MODEbits.STSEL = 0; // 1-Stop bit
U2MODEbits.PDSEL = 0 ; // No Parity 8 bit data
U2MODEbits.ABAUD = 0; // Auto-Baud Disabled
U2MODEbits.BRGH = 1; // High Speed Mode
U2MODEbits.URXINV = 0;
U2STAbits.UTXINV = 0;
U2BRG = BRGVAL; // Baud Rate Setting for 9600
U2MODEbits.UARTEN = 1; //Enable UART module
U2STAbits.UTXEN = 1; //Enable UART TX
unsigned char putU2(unsigned char c)
{
while (U2STAbits.TRMT == 0)
{
}
while ( CTS);
while ( U2STAbits.UTXBF);
U2TXREG = c & 0xF;
U2TXREG = (c >> 4) & 0xF;
return c;
}
If I am sedning that data splited to 4 bits I can see the data correct on the PC( c# serial port application)
But it should not be split into two writes to U2TXREG.
I am not 100% sure that the FCY is 16000000 but this is the only value that give me reasonable result.
What could be the problem?
For PIC24H, in UART high speed mode ( BRGH = 1 ) to get correct value of BRGVAL you need to divide by 4, not 16. Change the formula on line 3. Also, it is helpful to be 100% sure about clock rate; if you didn't change configuration bits it is likely 8 MHz, not 16.
Related
I'm working on a Distance measurement program using an AVR microcontroller. I use a 16x2 LCD and an ultrasonic sensor along with ATMEGA32A. I wrote a code to display the distance from the Ultrasonic HC-SR04 on the LCD screen, but it gives me false readings, it increases the distance when the object is very near and vice versa. I just want an accurate reading.
Ultrasonic datasheet
ATMEGA32A Datasheet
#include <avr/io.h>
#include <avr/interrupt.h>
#include <MrLcd/MrLCDmega32.h>
#define F_CPU 1000000
#include <util/delay.h>
#include <stdlib.h>
#define Trigger_pin PD0 /* Trigger pin */
static volatile int pulse = 0;
static volatile int i = 0;
int main(void)
{
Initialise();
DDRD = 0b11111011;
_delay_ms(50);
GICR |= 1<<INT0;
MCUCR |= 1<<ISC00;
int16_t count_a = 0;
char show_a[16];
sei();
while(1)
{
PORTD |= (1<<Trigger_pin);
_delay_us(10);
PORTD &= ~(1<<Trigger_pin);
count_a = pulse/58;
Send_A_String("Distance Sensor");
GoToMrLCDLocation(1,2);
Send_A_String("Distance=");
itoa(count_a,show_a,10);
Send_A_String(show_a);
Send_A_String(" ");
GoToMrLCDLocation(13,2);
Send_A_String("cm");
GoToMrLCDLocation(1,1);
}
}
ISR(INT0_vect)
{
if(i == 1)
{
TCCR1B = 0;
pulse = TCNT1;
TCNT1 = 0;
i = 0;
}
if(i==0)
{
TCCR1B |= 1<<CS10;
i = 1;
}
}
I tried to change the trigger pin definition and define it in the code itself but still no progress.
Update: I changed a bit more in the code but I'm getting hex values when the distance is more than 9, for example, 10 is being displayed as 1e.
This is for initialise function
void Initialise(void)
{
DataDir_MrLCDsControl|=1<<LightSwitch|1<<ReadWrite|1<<BipolarMood; //these information will go towards the LCD
_delay_ms(15); // Wait for the LCD to start
Send_A_Command(0x01); // to clear the screen
_delay_ms(2);
Send_A_Command(0x38); // TO tell LCD about 8 data lines
_delay_us(50);
Send_A_Command(0b00001110); //Some cursor command
_delay_us(50);
}
You are sending pulses at a very rapid rate (determined solely by the display update time), and they are asynchronous to the time/counter reset. You have no idea which pulse triggered the interrupt and it did not start at the same time as the timer.
I would suggest that you reset the counter at the start of the pulse, and capture the counter value on interrupt. When the time has exceeded the maximum range, send a new pulse:
First define some constants:
#define PULSES_PER_CMx100 (F_CPU * 100 / 68600)
#define MAX_RANGE_CM 300
#define MAX_RANGE_COUNT ((MAX_RANGE_CM * PULSES_PER_CMx100) / 100)
Then your measure/display loop might look like:
pulse = 1 ; // dummy start
GICR &= ~(1<<INT0) ; // Disable INT0
for(;;)
{
// Ready for new measurement?...
if( pulse != 0 )
{
// Send pulse and reset timer
PORTD |= (1<<Trigger_pin) ;
pulse = 0 ;
TCNT1 = 0 ;
_delay_us(10);
PORTD &= ~(1<<Trigger_pin) ;
// Wait for echo pulse interrupt...
GIFR |= 1<<INTF0; // Clear INT0 pending flag
GICR |= 1<<INT0 ; // Enable INT0
}
else // When measurement available...
{
int distance_cm = pulse * 100 / PULSES_PER_CMx100 ;
// display distance
...
}
// If out of range, timeout, send a new pulse
if( TCNT1 > MAX_RANGE_COUNT )
{
// Force a new pulse to be triggered
pulse = 1 ;
}
}
And the ISR:
ISR(INT0_vect)
{
pulse = TCNT1; // Capture time on interrupt
GICR &= ~(1<<INT0) ; // Disable further interrupts
}
Now bear in mind that that method will take measurements as fast as possible and since you are displaying them for human reading, that is rather unnecessary. You might simply put a delay in the loop - making the pulse timeout unnecessary, or better you could take the mean of multiple measurements to get a more robust measurement, or use a moving average window, with outlier rejection.
I'm trying to connect to an STM8 using uart. The STM seems to transmit data OK, but what it receives seems to be mostly junk, and often seems to receive 2 bytes at once. Here's the code:
#include "../stm8.h"
//
// Setup the system clock to run at 16MHz using the internal oscillator.
//
void InitialiseSystemClock()
{
CLK_ICKR = 0; // Reset the Internal Clock Register.
CLK_ICKR |= CLK_ICKR_HSIEN ; // Enable the HSI.
CLK_ECKR = 0; // Disable the external clock.
while ((CLK_ICKR & CLK_ICKR_HSIRDY) == 0); // Wait for the HSI to be ready for use.
CLK_CKDIVR = 0; // Ensure the clocks are running at full speed.
CLK_PCKENR1 = 0xff; // Enable all peripheral clocks.
CLK_PCKENR2 = 0xff; // Ditto.
CLK_CCOR = 0; // Turn off CCO.
CLK_HSITRIMR = 0; // Turn off any HSIU trimming.
CLK_SWIMCCR = 0; // Set SWIM to run at clock / 2.
CLK_SWR = 0xe1; // Use HSI as the clock source.
CLK_SWCR = 0; // Reset the clock switch control register.
CLK_SWCR |= CLK_SWCR_SWEN; // Enable switching.
while ((CLK_SWCR & CLK_SWCR_SWBSY) != 0); // Pause while the clock switch is busy.
}
//
// Setup the UART to run at 115200 baud, no parity, one stop bit, 8 data bits.
//
// Important: This relies upon the system clock being set to run at 16 MHz.
//
void init_uart()
{
//
// Clear the Idle Line Detected bit in the status register by a read
// to the UART1_SR register followed by a Read to the UART1_DR register.
//
//unsigned char tmp = UART1_SR;
//tmp = UART1_DR;
//UART1_SR = 0xC0; // mcarter set to default value
//
// Reset the UART registers to the reset values.
//
UART1_CR1 = 0;
UART1_CR2 = 0;
UART1_CR4 = 0;
UART1_CR3 = 0;
UART1_CR5 = 0;
UART1_GTR = 0;
UART1_PSCR = 0;
//
// Now setup the port to 115200,n,8,1.
//
// clear certain bits
UART1_CR1 &= ~UART1_CR1_M ; // 8 Data bits.
UART1_CR1 &= ~UART1_CR1_PCEN; // Disable parity
// stop bits
UART1_CR3 &= 0b11001111; // unmask the stop bit to default (1 stop bit)
//UART1_CR3 |= 0b00100000; // two stop bits
//UART1_CR3 |= 0b00110000; // 1.5 stop bits
//UART1_CR3 &= ~UART1_CR3_STOP; // 1 stop bit.
#if 1 //115200 baud
//UART1_BRR2 = 0x0a; // given in original example
UART1_BRR2 = 0x0b; // Set the baud rate registers to 115200 baud
UART1_BRR1 = 0x08; // based upon a 16 MHz system clock.
#else // 9600 baud, but seems to be worse than 115200
UART1_BRR2 = 0x03;
UART1_BRR1 = 0x69;
#endif
//
// Disable the transmitter and receiver.
//
//UART1_CR2_TEN = 0; // Disable transmit.
//UART1_CR2_REN = 0; // Disable receive.
//
// Set the clock polarity, lock phase and last bit clock pulse.
//
UART1_CR3 |= UART1_CR3_CPOL;
UART1_CR3 |= UART1_CR3_CPHA;
//UART1_CR3 |= UART1_CR3_LBCL; // this seems to cause problems
UART1_CR2 |= UART1_CR2_TEN; // enable transmit
UART1_CR2 |= UART1_CR2_REN; // enable receive
UART1_CR3 |= UART1_CR3_CLKEN; // unable uart clock
}
char uart_getc()
{
while((UART1_SR & UART1_SR_RXNE)==0); // Block until char rec'd
//char c = UART1_DR;
//return c;
return UART1_DR;
}
void uart_putc(char c)
{
while((UART1_SR & UART1_SR_TXE)==0); // Wait for transmission complete
UART1_DR = c; // transmit char
}
void UARTPrintf(char *message)
{
char *ch = message;
while (*ch)
uart_putc(*ch++);
}
void main()
{
disable_interrupts();
InitialiseSystemClock();
init_uart();
enable_interrupts();
UARTPrintf("Uart example: you type, I echo\n\r");
while (1)
{
//continue;
char c = uart_getc();
uart_putc(c);
//UARTPrintf("Hello from my microcontroller....\n\r");
//for (long counter = 0; counter < 2500000; counter++);
}
}
Relevant declaration headers are:
#define UART1_SR *(uchar*)(0x5230)
#define UART1_DR *(uchar*)(0x5231)
#define UART1_BRR1 *(uchar*)(0x5232)
#define UART1_BRR2 *(uchar*)(0x5233)
#define UART1_CR1 *(uchar*)(0x5234)
#define UART1_CR2 *(uchar*)(0x5235)
#define UART1_CR3 *(uchar*)(0x5236)
#define UART1_CR4 *(uchar*)(0x5237)
#define UART1_CR5 *(uchar*)(0x5238)
#define UART1_GTR *(uchar*)(0x5239)
#define UART1_PSCR *(uchar*)(0x523A)
#define UART1_CR1_M (1<<4)
#define UART1_CR1_PCEN (1<<2)
#define UART1_CR2_TEN (1<<3)
#define UART1_CR2_REN (1<<2)
#define UART1_CR3_STOP 4
#define UART1_CR3_CPOL (1<<2)
#define UART1_CR3_CPHA (1<<1)
#define UART1_CR3_LBCL (1<<0)
#define UART1_CR3_CLKEN (1<<3)
#define UART1_SR_TXE (1<<7)
#define UART1_SR_TC (1<<6)
#define UART1_SR_RXNE (1<<5)
I'm not really sure about stop bits, and all that. It's just "regular" serial communication.
I found that if I uncommented the line
//UART1_CR3 |= UART1_CR3_LBCL; // this seems to cause problems
then the stm8 prints out a continuous stream of junk. But with it commented out, the mcu seems to correctly know that there has been a transmission. There doesn't seem to be any pattern as to what it sees, though.
Hmm. The offending line seems to be
UART1_CR3 |= UART1_CR3_CLKEN;
It's purpose seem to be to "enable the SCLK pin". I don't really understand what's going on here, but according to a pinout diagram, one of the purposes of pin PD4 is UART1_CK. So you can attach a UART clock to the STM8 and this enables it?? And thereby causes problems if a clock isn't attached. It doesn't make that much sense, really; I didn't know uarts could have external clocks.
Anyway, commenting out the line seems to have fixed things.
I am currently working for the first time with a PIC microcontroller. In the code I specified exactly which PIC, compiler, etc I am using. Maybe this is of help.
I am trying to set up UART communication on the PIC32 and send a hex code like 0x41 for example to a terminal on my computer through RS232. To convert the signal from the PIC UART to RS232 levels I am using a MAX232EPE.
At the moment I am running into the problem that when I send 0x41 for example from the PIC32 to the terminal or vice versa, the received data doesn't match. I think this being caused by a mistake in my baud rate settings, but I am not sure. Could someone please look over my code and see if someone can see a problem? Did I forget to define something? Did I define something wrong? Did I mis calculate the baud rate?
P.S. I know the data being received doesn't match the data send because i checked in the "watches" in debug mode in mplab and when I echo the data send from the terminal to the PIC32 back to the terminal it doesn't match either.
The Delay and interrupt code can be ignored, they are working as expected, so I really believe the problem has to do with the initial setting of the PIC/buad rate.
I hope this is clear enough, any help is very much appreciated
Thanks,
See code below
/*
The configuration below and in void UART1_Init should set up the UART correctly.
I want to achieve a buadrate of 9600. My external Crystal is 8MHz. So:
FPLLIDIV=2, FPLLMUL=20, FPLLODIV=1, FPBDIV=2, FNOSC=PRIPLL, BRGH = 0, and U1BRG = 259.
This should give me the desired baudrate of 9600.
- ((8MHz / 2) * 20)/2) = 40MHz PBclk.
- U1BRG = (PBclk/(16*Buad rate))-1 so 259
- 16*Buad rate because BRGH = 0
PIC32MX795F512H
MPLAB X IDE V3.26
XC32 Compiler
PICKit3
*/
#include <stdio.h>
#include <stdlib.h>
#include <xc.h>
#include <plib.h>
// Give useful names to pins
#define LED1_TRIS TRISDbits.TRISD6
#define LED1 LATDbits.LATD6
#define UART1TX_TRIS TRISDbits.TRISD3
#define UART1RX_TRIS TRISDbits.TRISD2
#define FOSC 8000000 // Crystal frequency = 8 MHz
#define SYS_FREQ (80000000UL) // SYSCLK is 80 MHz
#define GetSystemClock() (FOSC) // For delay
#pragma config FPLLIDIV=DIV_2 // PLL Input Divider Value (Divide by 2)
#pragma config FPLLMUL=MUL_20 // Phase-Locked Loop (PPL) muiltiplier, multiplier of 20
#pragma config FPLLODIV=DIV_1 // Postscaler for PLL, output divided by 1
#pragma config FPBDIV=DIV_2 // 2 = PBCLK is SYSCLK divided by 2 (80MHz/2 = 40MHz)
#pragma config FWDTEN=OFF // Watch Dog Timer (WDT) is not enabled. It can be enabled by software
#pragma config CP=OFF // Code-Protect, 1 = OFF/Disabled
#pragma config BWP=OFF // Boot Flash Write-protect, 1 = OFF/Disabled
#pragma config POSCMOD=XT // Primary oscillator configuration, HS = HS Oscillator mode selection
#pragma config FNOSC=PRIPLL // Oscillator selection, PRIPLL = Primary Oscillator with PLL module
#pragma config OSCIOFNC=OFF // CLKO output disabled
#pragma config FSOSCEN=OFF // Disable secondary Oscillator
int UART_RX_Count; // Counter variable for the UART1 receiver interrupt
int UART_TX_Count; // Counter varible for the UART1 transmitted interrupt
unsigned char RD_SER_NUM; // Variable to store command to read serial number
unsigned char UART_RX_OUTPUT; // Variable to store the UART output
unsigned char i;
void UART1_Init(void){
// UART1 initialization
U1MODEbits.ON = 1; // UART1 is enabled
U1MODEbits.SIDL = 0; // Continue operation in idle mode
U1MODEbits.IREN = 0; // Disable IrDA (IrDA Encoder and Decoder Enable bit)
U1MODEbits.RTSMD = 1; // !U1RTS! pin is in Simplex mode, 0 = !U1RTS! pin is in Flow Control mode
U1MODEbits.UEN = 0; // UxTX and UxRX pins are enabled and used; UxCTS and UxRTS/UxBCLK pins are controlled by corresponding bits in the PORTx register
U1MODEbits.WAKE = 1; // Enable Wake-up on Start bit Detect During Sleep Mode bit
U1MODEbits.LPBACK = 0; // UARTx Loopback Mode Select bit, 0 = disabled, loopback = UxTX output is internally connected to the UxRX input
U1MODEbits.PDSEL = 2; // Parity and Data Selection bits, 10 = 8-bit data, odd parity
U1MODEbits.STSEL = 0; // Stop Selection bit, 0 = 1 stop bit
U1MODEbits.BRGH = 0; // High Baud Rate Enable bit, 0 = Standard Speed mode 16x baud clock enabled
U1MODEbits.RXINV = 1; // Receive Polarity Inversion bit, 1 = UxRX Idle state is 0
U1STAbits.URXEN = 1; // 1 = UART1 receiver is enabled. U1RX pin is controlled by UARTx (if ON = 1)
U1STAbits.UTXEN = 1; // 1 = UART1 transmitter is enabled. U1TX pin is controlled by UARTx (if ON = 1)
U1STAbits.UTXINV = 1; // Transmit Polarity Inversion bit, 1 = UxTX Idle state is 0
U1STAbits.ADM_EN = 0; // 0 = Automatic Address Detect mode is disabled
U1BRG = 259; // Baud Rate Divisor bits (0-15 bits), set baud rate, 9600 # 40 MHz PBclk
__builtin_disable_interrupts(); // Tell CPU to stop paying attention to interrupts
INTCONbits.MVEC = 1; // Multi Vector interrupts
U1STAbits.URXISEL = 0; // 0x = Interrupt flag bit is set when a character is received
U1STAbits.UTXISEL = 1; // 01 = Interrupt flag bit is set when all characters have been transmitted
IPC6bits.U1IP = 5; // Set UART1 priority 5 of 7
IPC6bits.U1IS = 0; // Set UART1 sub priority to 0
IFS0bits.U1RXIF = 0; // Clear UART1 RX interrupt flag
IFS0bits.U1TXIF = 0; // Clear UART1 TX interrupt flag
IEC0bits.U1RXIE = 1; // Enable UART1 RX ISR
__builtin_enable_interrupts(); // Tell CPU to start paying attention to interrupts again
UART_RX_Count = 0; // Set initial UART1 received interrupts count to 0
UART_TX_Count = 0; // Set initial UART1 transmit interrupts count to 0
}
void __ISR(_UART_1_VECTOR, IPL5SRS) UART1_INT(void){
if(INTGetFlag(INT_U1RX)){ // Check if UART1 RX interrupt was triggered
LED1 = ~LED1; // Toggle LED1
UART_RX_Count++; // Add 1 to UART1 RX interrupt occurrence counter
// UART_RX_OUTPUT = U1RXREG; // Read UART1 RX buffer/register
U1TXREG = U1RXREG; // Transmit the received data back
// U1STAbits.OERR = 0; // Clear UART1 buffer overflow
IFS0bits.U1RXIF = 0; // Clear UART1 RX interrupt flag
}else{
if(INTGetFlag(INT_U1TX)){ // Check if UART1 TX interrupt was triggered
UART_TX_Count++; // Add 1 to UART1 TX interrupt occurrence counter
IEC0bits.U1TXIE = 0; // Disable UART1 TX ISR
IFS0bits.U1TXIF = 0; // Clear UART1 TX interrupt flag
}
}
}
// DelayMs creates a delay of given milliseconds using the Core Timer
void DelayMs(WORD delay){
unsigned int int_status;
while( delay-- ){
int_status = INTDisableInterrupts();
OpenCoreTimer(GetSystemClock() / 200);
INTRestoreInterrupts(int_status);
mCTClearIntFlag();
while( !mCTGetIntFlag() );
}
mCTClearIntFlag();
}
int main(){
UART1_Init(); // Call the initializations function of UART1
LED1_TRIS = 0; // Set the LED1 as an output
UART1TX_TRIS = 0; // Set UART1 TX pin as output
UART1RX_TRIS = 1; // Set UART1 RX pin as input
LED1 = 0; // Turn off LED1
while(1){
// DelayMs(1000);
// IEC0bits.U1TXIE = 1; // Enable UART1 TX ISR
// U1TXREG = 0x41; // Send command to U1TXREG
}
return 0;
}
As You are using PIC32MX795F512H, You can use the MPLAB Harmony framework tool for creating your project. So that you need not to play on bit level and stuck in minor error or most probabaly typo error.
Its convinient to generate drivers and all framework properly.
Thanks and regards
Ravi
Using Harmony will actually help you avoid simple errors like the one you have encountered. Especially for the clocks you even have auto calculating functions decreasing your implementation time significantly.
I am trying to read several PWM signals from an RC receiver into an ATMega 2560. I am having trouble understanding how the ICRn pin functions as it appears to be used for all three compare registers.
The RC PWM signal has a period of 20ms with a HIGH pulse of 2ms being a valid upper value and 1ms being a valid lower value. So the value will sweep from 1000us to 2000us. The period should begin at the rising edge of the pulse.
I have prescaled the 16MHz clock by 8 to have a 2MHz timer an thus should be able to measure the signal to 0.5us accuracy which is sufficient for my requirements.
Please note that I am having not problems with PWM output and this question is specifically about PWM input.
My code thus far is attached below. I know that I will have to use ICR3 and an ISR to measure the PWM values but I am unsure as to the best procedure for doing this. I also do not know how to check if the value measured is from PE3, PE4, or PE5. Is this code right and how do I get the value that I am looking for?
Any help would be greatly appreciated.
// Set pins as inputs
DDRE |= ( 0 << PE3 ) | ( 0 << PE4 ) | ( 0 << PE5 );
// Configure Timers for CTC mode
TCCR3A |= ( 1 << WGM31 ) | ( 1 << WGM30 ); // Set on compare match
TCCR3B |= ( 1 << WGM33 ) | ( 1 << WGM32 ) | ( 1 << CS31); // Set on compare match, prescale_clk/8
TCCR3B |= ( 1 << ICES5 ) // Use rising edge as trigger
// 16 bit register - set TOP value
OCR3A = 40000 - 1;
OCR3B = 40000 - 1;
OCR3C = 40000 - 1;
TIMSK3 |= ( 1 << ICIE3 );
I had forgotten to post my solution a few months ago so here it is...
I used a PPM receiver in the end so this code can easily edited to read a simple PWM.
In my header file I made a structure for a 6 channel receiver that I was using for my project. This can be changed as required for receivers with more or less channels.
#ifndef _PPM_H_
#define _PPM_H_
// Libraries included
#include <stdint.h>
#include <avr/interrupt.h>
struct orangeRX_ppm {
uint16_t ch[6];
};
volatile unsigned char ch_index;
struct orangeRX_ppm ppm;
/* Functions */
void ppm_input_init(void); // Initialise the PPM Input to CTC mode
ISR( TIMER5_CAPT_vect ); // Use ISR to handle CTC interrupt and decode PPM
#endif /* _PPM_H_ */
I then had the following in my .c file.
// Libraries included
#include <avr/io.h>
#include <stdint.h>
#include "ppm.h"
/* PPM INPUT
* ---
* ICP5 Pin48 on Arduino Mega
*/
void ppm_input_init(void)
{
DDRL |= ( 0 << PL1 ); // set ICP5 as an input
TCCR5A = 0x00; // none
TCCR5B = ( 1 << ICES5 ) | ( 1 << CS51); // use rising edge as trigger, prescale_clk/8
TIMSK5 = ( 1 << ICIE5 ); // allow input capture interrupts
// Clear timer 5
TCNT5H = 0x00;
TCNT5L = 0x00;
}
// Interrupt service routine for reading PPM values from the radio receiver.
ISR( TIMER5_CAPT_vect )
{
// Count duration of the high pulse
uint16_t high_cnt;
high_cnt = (unsigned int)ICR5L;
high_cnt += (unsigned int)ICR5H * 256;
/* If the duration is greater than 5000 counts then this is the end of the PPM signal
* and the next signal being addressed will be Ch0
*/
if ( high_cnt < 5000 )
{
// Added for security of the array
if ( ch_index > 5 )
{
ch_index = 5;
}
ppm.ch[ch_index] = high_cnt; // Write channel value to array
ch_index++; // increment channel index
}
else
{
ch_index = 0; // reset channel index
}
// Reset counter
TCNT5H = 0;
TCNT5L = 0;
TIFR5 = ( 1 << ICF5 ); // clear input capture flag
}
This code will use an trigger an ISR every time ICP5 goes from low to high. In this ISR the 16bit ICR5 register "ICR5H<<8|ICR5L" holds the number of pre-scaled clock pulses that have elapsed since the last change from low to high. This count is typically less than 2000 us. I have said that if the count is greater than 2500us (5000 counts) then the input is invalid and the next input should be ppm.ch[0].
I have attached an image of PPM as seen on my oscilloscope.
This method of reading PPM is quite efficient as we do not need to keep polling pins to check their logic level.
Don't forget to enable interrupts using the sei() command. Otherwise the ISR will never run.
Let's say you want to do the following (I'm not saying this will allow you to accurately measure the PWM signals but it might serve as example on how to set the registers)
Three timers running, which reset every 20 ms. This can be done by setting them in CTC mode for OCRnA: wgm3..0 = 0b0100.
//timer 1
TCCR4A = 0;
TCCR1B = (1<<CS11) | (1<<WGM12);
OCR1A = 40000 - 1;
//timer 3 (there's no ICP2)
TCCR3A = 0;
TCCR3B = (1<<CS31) | (1<<WGM32);
OCR3A = 40000 - 1;
//timer 4
TCCR4A = 0;
TCCR4B = (1<<CS41) | (1<<WGM42);
OCR4A = 40000 - 1;
Now connect each of the three pwm signals to their own ICPn pin (where n = timer). Check the datasheet for the locations of the different ICPn pins (i'm pretty sure it's not PE3, 4, 5)
Assuming the pwm signals start high at t=0 and go low after their high-time for the remainder of the period. You want to measure the high-time so we trigger an interrupt for each when a falling edge occurs on the ICPn pin.
bit ICESn in the TCCRnB register set to 0 will select the falling edge (this is already done in the previous code block).
To trigger the interrupts, set the corresponding interrupt enable bits:
TIMSK1 |= (1<<ICIE1);
TIMSK3 |= (1<<ICIE3);
TIMSK4 |= (1<<ICIE4);
sei();
Now each time an interrupt is triggered for ICn you can grab the ICRn register to see the time (in clockperiods/8) at which the falling edge occurred.
I have got the UART TX working on one pic but cannot get the UART RX working on another PIC. My plan is to have the first PIC send data to the second PIC.
My initialisation code for the first PIC TX is,
Code:
void configure_TX_port(){
/*Port configurations*/
OSCCON = 0X68;
//Push button
TRISC3 = 1;
INLVLC3 = 0;
ANSC3 = 0;
//Led output
TRISC2 = 0;
//TX output
TRISA2 = 0;
ANSA2 = 0;
/*PPS setup for RA2*/
PPSLOCK = 0x55;
PPSLOCK = 0xAA;
PPSLOCK = 0;
RA2PPS = 0x14;
PPSLOCK = 0x55;
PPSLOCK = 0xAA;
PPSLOCK = 1;
/*UART configuration*/
TXEN = 1;
SYNC = 0;
SPEN = 1;
TXSTA = (0x4|0x20);
SPBRG = (int)(4000000L/(16UL * 9600) -1);
}
My send data to the tx code is
Code:
void putch(unsigned char byte) {
/* output one byte */
while (!TXIF) /* set when register is empty */
TXREG = byte;
}
My initialisation code for the second PIC RX is,
void configure_RX_port(){
/*Port configurations*/
OSCCON = 0X68;
//Led output
TRISC3 = 0;
//RX input
TRISC5 = 1;
ANSC5 = 0;
/*UART configuration*/
CREN = 1;
SYNC = 0;
SPEN = 1;
TXSTA = (0x4|0x20);
RCSTA = 0x90;
SPBRG = (int)(4000000L/(16UL * 9600) -1);
}
My receive data code is,
unsigned char getch(void) {
/* retrieve one byte */
unsigned char ret;
while (!RCIF) { /* set when register is not empty */
}
ret = RCREG;
return ret;
}
When I debug the code the getch function gets blocked waiting on a character but my other PIC is sending data. On this PIC RC5 is a designated RX pin so I dont think I have to do any pps configuration.
Rahul
TX1STA = 0b00100100; This enablex TX (TXEN=1) and high baud rate (BRGH = 1)
RC1STA = 0b10000000; This enable the serial port (SPEN = 1)
The only important missing part is your Clock setting and the baudrate you want to have.
I saw 4000000 in the formula, means 4MHz, and /9600, so assume 9600BDS).
Result = 0x25.
SPBRGL = 0x25;
SPBRGH = 0;
This way, your TX should work. Your tx function is good.
Be sure to configure RX and TX pins as DIGITAL by disabling ANSELA, ANSELB and ANSELC.
Your PIC also use PPS, so be sure to configure it the right way.
*********EDITED POST, RECEIVE CONDITION************
The only difference here to get a working receiver is to enable the continuous receiver
bit, CREN.
RC1STA = 0b10010000; //Enable serial port(SPEN) and continuous receive(CREN).
Be sure to set RX pin (RC5 in your case) as an INPUT (TRISC5 = 1) so that it can read any entering data. You should also consider doing an interrupt routine instead of polling the receiver flag bit. That way you're sure not to skip any entering data.
By default at reset all pins on PIC16F1704 are set as analog.
So clear coresponding bits of RX and TX pins in registers ANSELA, ANSELB and ANSELC to set tham as digital.
You look to be using asynchronous mode with SYNC = 0, but do not set TXEN = 1.
Setting CREN = 1 only overrides TXEN in synchronous mode. Try setting TXEN = 1.
I added the following line, TXSTA = (0x4|0x20); to the receiver PIC code and it works now. There is no need for
CREN = 1;
SYNC = 0;
SPEN = 1;
as its setting the same bits.