2.9 UART Driver

• Add UART to the project

• Configure:

  1. The UART as described in the example.

  2. Best practice: Enable (weak)pullup on UART Rx pin  

• Generate the code

• Add the code snippet(s) to the application code

• Program the board

1. Add UART

• Dependency Selector:

  1. UART PLIB Selector: Select the UART connected to Serial/CDC port.

• Configuration Settings:

  1. Redirect STDIO to UART (for printf support): Yes

• Pins: (For all pins check board schematics)

  1. Pin Grid View: Select pin for UART Transmit - Tx.

• Inerrupt Manger: (for AVR)

  1. Global Interrupt Enable: Yes.

#include "mcc_generated_files/system/system.h"  

void UART_print_loop(uint8_t count)
{
    int i;
    for(i = 0; i < count; i++)
    {
        printf("%d. Hello World!\n",i);
    }
}

void main(void)
{
    SYSTEM_Initialize();
    UART_print_loop(5); 

    while(1){}    
}

1. Add UART

• Dependency Selector:

  1. UART PLIB Selector: Select the UART connected to Serial/CDC port.

• Configuration Settings:

  1. Custom Name: UARTx renamed to UART

• Pins: (For all pins check board schematics)

  1. Pin Grid View: Select pin for UART Transmit - Tx.

• Inerrupt Manger: (for AVR)

  1. Global Interrupt Enable: Yes.  

#include "mcc_generated_files/system/system.h"  
#include <string.h>

char msg[] = "Hello World!\r\n";
void UART_write_string(const char *msg)
{
    for(uint8_t i = 0; i < strlen(msg); i++)
    {
        while(!UART.IsTxReady());
        UART.Write(msg[i]);
    }
}

void main(void)
{
    SYSTEM_Initialize();
    UART_write_string(msg); 

    while(1){}    
}

1. Add UART

• Dependency Selector:

  1. UART PLIB Selector: Select the UART connected to Serial/CDC port.

• Configuration Settings:

  1. UART: UARTx renamed to UART (Custom name field)

  2. Redirect STDIO to UART (for printf support): Yes

• Interrupt Settings:

  1. Interrupt Driven: Yes.

  2. Software Transmit Buffer Size: 128

• Pins: (For all pins check board schematics)

  1. Pin Grid View: Select pin for UART Transmit - Tx.

  2. Pin Grid View: Select LED pin as output.  

  3. Pins: Rename Custom Name to "LED".  

• Inerrupt Manger: (for AVR)

  1. Global Interrupt Enable: Yes.  

• Control LED using terminal commands. The commands are case sensitive.

  1. Send "ON" to turn the LED.

  2. Send "OFF" to turn it off.

#include "mcc_generated_files/system/system.h"
#include <string.h>

#define MAX_COMMAND_LEN 8
uint8_t command[MAX_COMMAND_LEN];
uint8_t index = 0;
uint8_t read_msg;

void UART_executeCommand(char *command)
{
    if(strcmp(command, "ON") == 0)
    {
        LED_SetLow();
        printf("OK, LED ON.\r\n");
    }
    else if (strcmp(command, "OFF") == 0)
    {
        LED_SetHigh();
        printf("OK, LED OFF.\r\n");
    }
    else
    {
        printf("Incorrect command.\r\n");
    }
}

void UART_ProcessCommand(void)
{
    
    if(UART.IsRxReady())
    {
        read_msg = UART.Read();
        if(read_msg != '\n' && read_msg != '\r')
        {
            command[index++] = read_msg;
            if((index) > MAX_COMMAND_LEN)
            {
                (index) = 0;
            }
        }
        if(read_msg == '\n')
        {
            command[index] = '\0';
            index = 0;
            UART_executeCommand(command);
        }
    }
}

int main(void)
{
    SYSTEM_Initialize();
    
    UART.RxCompleteCallbackRegister(&UART_ProcessCommand);
    
    printf("In the terminal, send 'ON' to turn the LED on, and 'OFF' to turn it off.\r\n");
    printf("Note: commands 'ON' and 'OFF' are case sensitive.\r\n");
    
    INTERRUPT_GlobalInterruptEnable();  /* Remove for AVR, enable in System>Interrupt Manager */
    
    while(1) 
    { }
}

1. Add UART

• Dependency Selector:

  1. UART PLIB Selector: Select the UART connected to Serial/CDC port.

• Configuration Settings:

  1. UART: UARTx renamed to UART (Custom name field)

  2. Redirect STDIO to UART (for printf support): Yes

• Interrupt Settings:

  1. Interrupt Driven: No.

• Pins: (For all pins check board schematics)

  1. Pin Grid View: Select pin for UART Transmit - Tx.

  2. Pin Grid View: Select LED pin as output.  

  3. Pins: Rename Custom Name to "LED".  

int main(void)
{
    SYSTEM_Initialize();
    
    printf("In the terminal, send 'ON' to turn the LED on, and 'OFF' to turn it off.\r\n");
    printf("Note: commands 'ON' and 'OFF' are case sensitive.\r\n");
    
    while(1)
    {
        UART_ProcessCommand();
    }
}

1. Add UART

• Dependency Selector:

  1. UART PLIB Selector: Select the UART connected to Serial/CDC port.

• Configuration Settings:

  1. UARTx renamed to UART (Custom name field)

  2. Redirect STDIO to UART (for printf support): Yes

• Pins: (For all pins check board schematics)

  1. Pin Grid View: Select pin for UART Transmit - Tx.

  2. Pin Grid View: Select pin for UART Receive - Rx.

  3. Best practice: Enable (weak)pullup on UART Rx pin

• Code modifications: usartx_status_t -> replace with reference to PLIB used. Find this by searching for "status" in uartx.c (for PIC) or usartx.c (for AVR)

#include "mcc_generated_files/system/system.h"

int main(void)
{
    SYSTEM_Initialize();
    
    printf("Hello World!\r\n");
    printf("Type characters in the terminal, to have them echoed back ...\r\n");
    
    while(1)
    {
        UART_echoCharacters();
    }
}