I've been working on a project which requires communication with my laptop and the microchip Pic 16f877a and the communication is not working properly, but When i put this example on Proteus 8 works just fine.
I don't have RS232(serial port) on my laptop, but i had bought TTL module. I use external oscillator 8MHz on the board and baud rate of 9600 bps.
When i connect with my laptop and i send to the TTL module the A symbol nothing hapens and when i send a couple of times A fast i recieve strange symbol like '?' or '#' back.
Here's the code for the Pic:
char x;
void main(){
TRISB = 0x00;
PORTB = 0x00;
UART1_Init(9600);
delay_ms(10);
while(1){
if(UART1_Data_Ready())
{
x = UART1_Read();
if(x == 'A')
{
PORTB = 0xFF;
UART1_Write(13);
UART1_Write_Text("A");
UART1_Write(13);
}
else
{
PORTB = 0x00;
}
}
x= '\0';
}
}
Can someone help me ? What's the problem ?
Two possibilities as far as I can see (assuming UART1_Init(9600); is a correct library function):
You don't have the Rx pin set up as an input; setting TRIS registers to 0 makes all the pins on that port outputs.
You are using incorrect parity.
Have you set a breakpoint at line
x = UART1_Read();
To see what you actually get in when you send from your terminal program?
Have you looked on youe scope to see what is actually coming in on the Rx pin?
delay_ms(10); is completely unnecessary.
give
SPBRG = 139
Refer this link to set the respective Baud Rate Generator
Related
I'm trying to program an atmega328p, but the SPI bus isn't working. It's not sending any data over the bus.
My code is as follows:
#include <asf.h>
#include <stdio.h>
#include <main.h>
int main (void)
{
board_init();
SPI_MasterInit();
DDRD = (1<<DDD5);
while(1)
{
PORTB &= ~(1<<DDB2);
SPI_MasterTransmit(0xAB);
PORTB |= (1<<DDB2);
PORTD ^= (1<<DDD5);
}
}
void SPI_MasterInit(void)
{
/* Set MOSI and SCK output, all others input */
DDRB = (1<<5) || (1<<3) || (1<<2);
/* Enable SPI, Master, set clock rate fck/16 */
SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0);
}
void SPI_MasterTransmit(char cData)
{
/* Start transmission */
SPDR = cData;
/* Wait for transmission complete */
while(!(SPSR & (1<<SPIF)));
}
I'm trying to send some random data over the bus (0xAB) to check if the bus works properly so I can add further code. In the while loop I also set a pin.
On my scope image I see no data being send on the SPI pin MOSI and the CLK pin is also not sending information. PB5 (the pin I'm inverting everytime I try to send data) is working and has a period of about 20 microseconds.
I'm programming the Atmega328p through an Atmel ICE. The programming interface is also through SPI, I read somewhere that this might be an issue. I'm not completely sure.
Does anyone know what might be the problem?
My first guess was not setting SS pin (PB2) as output. It may cause switching to the slave mode almost randomly. But it seems to be set as an output (it's not stated in comments).
But after closer look to this expression, it's obvious it's not set at all:
DDRB = (1<<5) || (1<<3) || (1<<2);
There is a huge difference between logical or || and bitwise or |.
Examples of writing to a port seem to always use the port number as a constant, eg,
OCR2A = 180;
How do you write to the port when the port is unknown until run time. For example,
int port = (buttonPressed) ? 0x3b : 0x3c;
portWrite( port, 180 );
What I cannot find is the funtion portWrite(). Does something like that exist?
Robert's answer has some imprecise assertions and an incomplete answer.
Writing directly to port registers you can ruin other settings of the port and sometimes cause permanent damage to controller.
Can ruin other settings: true, you have to know what you are doing (for instance what pins are on the port you are manipulating, and know what are the functions you want to keep.
Can cause permanent damage: not really, or better not because of the port manipulation. If you wire a short circuit to ground and then set it as an output to 1, you can damage it whether you are using the port register or the digitalwrite. You have to be careful in both ways.
Now, returning to your problem, the enumeration is one way, but since the PORTB, PORTC, PORTD are just short name for values, you can set a variable and then use it to indirectly access it.
The type for this kind of variable is a volatile pointer to a byte (volatile means that write and read operations cannot be optimized by the compiler, since the value can change even between two operations):
volatile uint8_t *variablePortRegister;
You just have to load it with the address (so with the & symbol) of the register you want to change:
variablePortRegister = &PORTC;
then use the pointer to change the value
PORTC = 0x12;
becomes
(*variablePortRegister) = 0x12;
This is a short example. For it to work, connect a LED with resistor on arduino pin 5 (bit 5 of PORTD). The LED on the board (labeled L) is connected to pin 13 (bit 5 of PORTB).
The sketch will make one of the two leds blink for five times, then switch to the other. Only port manipulation instructions are used, and you can find that the way to read the port is the same as the one to write it.
volatile uint8_t *myportreg;
unsigned long lastTime;
uint8_t counter;
void setup() {
DDRB |= 0x20;
DDRD |= 0x20;
PORTB = 0;
PORTD = 0;
counter = 99; // trigger the register change immediately
}
void loop() {
if (counter >= 10)
{
counter = 0;
if (myportreg == &PORTD)
myportreg = &PORTB;
else
myportreg = &PORTD;
}
if ((millis() - lastTime) > 500)
{
lastTime = millis();
// change bit 5 of register
*myportreg = 0x20 ^ (*myportreg);
counter++;
}
}
EDIT: as Robert pointed out, it's much better to "use" just the pins you need (in this case, bit 5 of port B and D) rather than setting the whole port; this way you minimize the risk of screwing up something else. This edit is already included in the above code, so the code is correct
The port is a bit in one particular register. If you know the register and the position of the port in that particular register you can try this:
register = (1<<port) || register
to set the port to 1 and
register = (1<<port)^-1 && register
to set the port to 0.
Of course, you will need a switch somewhere to determine the register and the bit of the port in the register given the port name.
When I try to receive the USART signal with my Silicon Labs CP210x USB to UART Bridge. The only thing I receive is:
<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
I use a ATmega128A3U. The test_LED (see code below) on port E pin 0 is working. I used a oscilloscope to check the uart signal. See picture here: http://imgur.com/dPxkdZ6
Does someone know a solution for this?
Does anyone know how to fix a framing error? (My UART software is giving this error)
CODE:
#define F_CPU (32000000UL) // CPU clock speed
#include <avr/io.h>
#include <util/delay.h>
void USARTF0_init() {
USARTF0_BAUDCTRLB = 0; //BSCALE is 0
USARTF0_BAUDCTRLA = 0xCF; //BSEL is 207
USARTF0_CTRLA = 0; //Disable interrupts
USARTF0_CTRLC = USART_CHSIZE_8BIT_gc; //8 data bits, no parity and 1 stop bit
USARTF0_CTRLB = USART_TXEN_bm | USART_RXEN_bm; // //Enable receive,transmit and high speed mode
PORTF_OUTSET = PIN3_bm; // Port F pin 3 as TX
PORTF_DIRSET = PIN3_bm; // TX pin as output
PORTF_OUTCLR = PIN2_bm; // Port F pin 2 as RX
PORTF_DIRCLR = PIN2_bm; // RX pin as input
}
void sendChar(char c) {
while( !(USARTF0_STATUS & USART_DREIF_bm) ); //Wait until DATA buffer is empty
USARTF0_DATA = c;
}
void sendString(char *text) {
while(*text) {
sendChar(*text++);
}
}
int main(void) {
USARTF0_init();
PORTE.DIRSET = PIN0_bm; // make port E pin 0 output (test_LED)
while(1)
{
_delay_ms(10);
sendString("Hello World!\n\r");
PORTE.OUTTGL = PIN0_bm; // test_LED Toggle
}
}
Code source: http://morf.lv/modules.php?name=tutorials&lasit=29
To recap the discussion, so it can useful to someone later.
If you have an oscilloscope, capture a trace for a simple test case, as #DrOctorooi has done with "#~00":
He has marked start and stop bits, and also the data bits (for serial/UART they're least-significant first)
This confirms that UART somehow works.
One should also confirm the voltage levels. 0-3.2V looks about right.
And the time base. On the captured trace it appears 1 bit takes 1.625ms, which means a baudrate of around 615. That's quite far from expected 9600. In fact, that's around 16 times slower.
Since the error has to do with time, the immediate questions are the MCU clock and UART clock dividers (and on more complex devices, and intermediate dividers and clocks).
It turns out the dividers were meant for the 32MHz clock, but this MCU has a clock of 2MHz when it comes out of reset (16 times slower, as we have seen above). Solution was to recalculate the dividers.
I need to transfer data serially from AT89s52 to Hyperterminal of PC.
For that I made a sample program to print "Hello" on the hyperterminal of my PC by programming the below given code inside 89s52 microcontroller and connecting it to my PC via serial port. Now when I am opening hyperterminal for the respective port, I should be seeing "Hello" printed on the screen multiple times, but what actually I am seeing is some garbage data getting printed.
This is the code I have used.
#include < AT89X52.H>
#include < STDLIB.H>
#include < STDIO.H>
unsigned int i;
void main (void)
{
TMOD = 0x20;
SCON = 0x50;
TH1 = 0xFD;
TL1 = 0xFD;
TR1 = 1;
TI = 1;
P1 = 0;
while (1)
{
puts("Hello\r");
P1 ^= 0x01; /* Toggle P1.0 each time we print */
for(i=0;i<25000;i++);
}
}
In the Hyper terminal I am not getting correct output i.e. Hello. Instead I am seeing some Garbage characters..
Can anybody help on this please..?
Can you See P1 is toggling? I would rather send a single character first and observe what is sending by using an oscilloscope. You should see a digital signal corresponding to the ASCII value of the character being split-out from the TX pin of the micro. Also you can check the baud rate (exact value) by using the scope. If you are convinced that the correct value is sent at the right baud rate it is most likely that you got a bad connection or perhaps the baud rate should slightly be changed.
I try to send the data from pc to the pic microcontroller. I am a beginner in PIC.
I send the data from hyperterminal and the data will display in the led in port B of PIC.
I used 10Mhz clock and the connection in 9600 baudrate.
here my uart.h program:
char UART_Init(const long int baudrate)
{
unsigned int x;
x = (_XTAL_FREQ - baudrate*64)/(baudrate*64);
if(x>255)
{
x = (_XTAL_FREQ - baudrate*16)/(baudrate*16);
BRGH = 1;
}
if(x<256)
{
SPBRG = x;
SYNC = 0;
SPEN = 1;
TRISC7 = 1;
TRISC6 = 1;
CREN = 1;
TXEN = 1;
return 1;
}
return 0;
}
char UART_TX_Empty()
{
return TRMT;
}
char UART_Data_Ready()
{
return RCIF;
}
char UART_Read()
{
while(!RCIF);
return RCREG;
}
void UART_Read_Text(char *Output, unsigned int length)
{
int i;
for(int i=0;i<length;i++)
Output[i] = UART_Read();
}
void UART_Write(char data)
{
while(!TRMT);
TXREG = data;
}
void UART_Write_Text(char *text)
{
int i;
for(i=0;text[i]!='\0';i++)
UART_Write(text[i]);
}
and this is my main program:
#include<htc.h>
#include<pic.h>
#define _XTAL_FREQ 10000000 //Clock Frequency
#include "uart.h"
void main()
{
TRISB = 0x00; //PORTB as Output
UART_Init(9600);
do
{
if(UART_Data_Ready())
PORTB = UART_Read();
__delay_ms(1000);
}while(1);
}
in hyperteminal I send data say 10010010 but the led in port B do not respond, are there any error in my program?
You have several steps: initialize UART, initialize LEDs, communicate over UART and setup your PC's UART. Which components have you successfully written and tested? You say you're a beginner, so what is the smallest functional program you have successfully executed on a PIC? I've been working with microcontrollers for years, but I still schedule about a whole day to get a single LED to turn on because it could be a software problem, a hardware problem, a voltage problem, an oscillator problem, a PCB problem or a compiler problem.
Here are the steps I take for microchip bring up:
Go over the oscillator section, the configuration bits section, the watchdog section and the pinout section (looking for VDD and VSS) in the datasheet. These are some of the hardest parts to get right. (A gotcha about the oscillator: just because you can program a chip, doesn't mean the oscillator is working because the programmer provides it's own clock.)
Write the bare-minimum code to turn on a single LED.
Write the bare-minimum code to make the LED blink (just use a for-loop delay for now, timers come later)
Write UART initialization code and transmit a single character, I use captial U because it's pretty in binary. TXREG = 'U';
Connect the UART to a PC and see if the hyperterminal sees the U. If it doesn't, I connect an oscilscope to the lines to make sure that the PIC is transmitting, that the PC transmits when I type characters and that the timing of the edges matches.
Within the PIC code, have the UART echo characters from the terminal. (TXREG = RXREG;), and then type on the hyperterminal and make sure the characters are echoed back.
One more note:
Do not have the PIC perform the SPBRG calculation. PIC16 are 8-bit processors and 10000000 requires 32-bits to store. There might be hiccups with the integer divison. It might not have a bug in it, but there's no need to have the PIC calculate it each time. Calculate it before-hand and hard-code the value.