How to send multiple data of ports through UART? - c

Question

I've changed the code for the receiver but the transmitter is pretty much the same, so in the receiver I've canceled the Interrupt and instead I read the data in a loop where I check every time for the state of the RC2IF_bit and the check is made by the same order the transmitter sends the data to make sure which port is sending data.
The problem is in simulation on proteus when I receive the data and output it on leds they work fine and the data is sent right but in the middle of the simulation when I watch it I found that they change states for a glance, for example if i send PORTA = 0X2D I receive the same value and the right leds turn-on but for a second they turn-off then they turn-on again, is this a problem in the code written.
/*This is the transmitter code*/
void UART2_TX_init (); //UART2 transmission initialization function porototype
void SEND_data (int output); //Send data function prototype
void main()
{
ANSELA = 0X00; //Disable analogue function on PORTA
ANSELE = 0X00; //Disable analogue function on PORTE
ANSELF = 0X00; //Disable analogue function on PORTF
TRISA = 0XFF; // SET PORTA AS INPUT (AUTOMATIC BUTTONS)
TRISB = 0XFF; //SET PORTB AS INPUT (OFF BUTTONS)
TRISD = 0XFF; //SET PORTD AS INPUT (MANUAL BUTTONS)
TRISE = 0XFF; //SET PORTE AS INPUT (HIGH BUTTONS)
TRISF = 0XFF; //SET PORTF AS INPUT (LOW BUTTONS)
TRISC = 0XFF; //SET PORTC AS INPUT (TRIP BUTTONS)
TRISG0_bit = 0; //set PORTC pin0 as output for MAX487 DE pin
PORTG.F0= 1; //set PORTC pin0 HIGH , set MAX487 as transmitter.
UART2_TX_init(); //call UART1 transmission initialization
while (1)
{
SEND_data(PORTA); //send data of automatic
delay_ms(10);
SEND_data(PORTB); //send data of off
delay_ms(10);
SEND_data(PORTD); //send daata of manual
delay_ms(10);
SEND_data(PORTE); //send data of high
delay_ms(10);
SEND_data(PORTF); //send data of low
delay_ms(10);
SEND_data(PORTC); //send data of TRIP
delay_ms(10);
}
}
/*This function takes the data needed to be send
as an integer. Wait for the TSR to be empty and
start the transmission*/
void SEND_data (int output)
{
while (!TRMT_TX2STA_bit){}; //checks if TSR is empty or not if empty TRMT_BIT is set and write to transmit register
TX2REG = output; //write data to be send in the transmission register
}
/*This function initializes the UART2 as an asynchronous
transmitter at a baud rate of 9600kbps*/
void UART2_TX_init ()
{
BAUD2CON = 0X08;
BRGH_TX2STA_bit = 1;
SP2BRGL = 207;
SYNC_TX2STA_bit = 0X00;
SPEN_RC2STA_bit = 0X01;
TRISG1_bit = 0X01;
TRISG2_bit = 0X01;
TXEN_TX2STA_bit = 0X01;
}
/*This is the receiver code*/
void UART2_RX_init (); // Receiver initialization function prototype
void main()
{
ANSELA = 0X00; // Disable analog function on PORTA
ANSELE = 0X00; // Disable analog function on PORTE
ANSELF = 0X00; // Disable analog function on PORTF
TRISA = 0X00; //set PORTA as output
TRISB = 0X00; //set PORTB as output
TRISD = 0X00; //set PORTD as output
TRISE = 0X00; //set PORTE as output
TRISF = 0X00; //set PORTF as output
TRISC = 0X00; //set PORTF as output
PORTA = 0x00; //clear PORTA
PORTB = 0x00; //clear PORTB
PORTD = 0x00; //clear PORTD
PORTE = 0x00; //clear PORTE
PORTF = 0x00; //clear PORTF
PORTC = 0x00; //clear PORTC
TRISG0_bit = 0x00; //set PORTC pin0 as output for MAX487 RE pin
PORTG.F0 = 0x00; // set PORTC pin0 as LOW , set MAX487 as receiver
UART2_RX_init(); //call receiver initialization function
while (1)
{
while (!RC2IF_bit) ; //check if the RCIF flag is up to tell if there is a new data
PORTA =~ RC2REG; //write the new data to the specified port
while (!RC2IF_bit) ;
PORTB =~ RC2REG;
while (!RC2IF_bit) ;
PORTD =~ RC2REG;
while (!RC2IF_bit) ;
PORTE =~ RC2REG;
while (!RC2IF_bit) ;
PORTF =~ RC2REG;
while (!RC2IF_bit) ;
PORTC =~ RC2REG;
}
}
/*This function initializes UART2 as an asynchronous
receiver at a baud rate of 9600kbps with continous
reception NO INTERRUPT ON RECEIVE*/
void UART2_RX_init ()
{
BAUD2CON = 0X08;
BRGH_TX2STA_bit = 1;
SP2BRGL = 207;
SYNC_TX2STA_bit = 0X00;
SPEN_RC2STA_bit = 0X01;
TRISG1_bit = 0X01;
TRISG2_bit = 0X01;
CREN_RC2STA_bit = 0X01;
}

Answer 1

First of all I want to say a few words about protocol design. Any communication protocol, if you want it to be reliable, should implement at least two things: frame synchronization and error checking. Okay, there are some specialized protocols that don't use frames and represent data as a continuous stream, but it's definitely not your case. So if you don't want to mess around with weird bugs, I highly recommend you to implement these things.
Now about your code. It looks like GET_data waits for the transmit register to be empty and writes to it one byte. I don't see anything wrong with that. But your receiver looks suspicious. You wait for the RCIF flag to be set and then read 5 times from the input register RCREG. But non-zero RCIF means that you received one byte. You can't wait for RCIF once and then read from RCREG multiple times. You should wait for RCIF before every read from RCREG.
I would be happy to give you an example of the working code, but I can't come up with a simple solution that will fit your current architecture.
I can give you example how to do it in a right way, but it will look totally different.

Answer 2

Some things:
the UART receive ISR should be as short as possible and just write the data into a buffer and contain absolutly not any delay routines.
use one interupt for every received byte.
start your frame with a startbyte. e.g 'S'
end your frame with a checksum byte.
do the portwrite in your mainloop after you detect a complete frame in your buffer (startbyte + databytes + correct chechsum)