Thread: Why SERCOM1_USART_Write function cannot be used twice in a row?

For a PIC32CM processor, I am trying to use the UART write function twice in a row. The project is built from Harmony3.

SERCOM1_USART_Write(char_array1, sizeof(char_array1));
SERCOM1_USART_Write(char_array2, sizeof(char_array2));

When the code is executed, only string1 is displayed.

I introduced various delay methods in between the two writes without success.

Does anyone have a solution or workaround?

Thanks.

How about posting more than 2 lines of code.

How is it called?
How are those variables declared and initialised?

Using sizeof() on a char array means you're going to send a \0, and that may be bad news to whatever is listening at the other end.

Maybe try it with strlen() instead.

Maybe you need to do something like this:

Code:

void print_string(const char *str)
{
    for (const char *s = str, *end = str + strlen(str); s != end; )
    {
        if (SERCOM1_USART_WriteFreeBufferCountGet() > 0)
            s += SERCOM1_USART_Write((uint8_t*)s, end - s);
        else
            // If you have a better way to wait, use it
            for (size_t i = 0; i < 1000000; ++i) ;  // busy wait
    }
}
 
void some_func()
{
    print_string("hello");
    print_string("world");
}

Originally Posted by boomeral

For a PIC32CM processor, I am trying to use the UART write function twice in a row. The project is built from Harmony3.

SERCOM1_USART_Write(char_array1, sizeof(char_array1));
SERCOM1_USART_Write(char_array2, sizeof(char_array2));

When the code is executed, only string1 is displayed.

I introduced various delay methods in between the two writes without success.

Does anyone have a solution or workaround?

Thanks.

Unless someone here has the exact same system, they can only speculate. One possibility which has been mentioned is that char_array2 is a pointer, in which case sizeof() will yield a value of probably 4. But then you would see the first four characters.

The thing to do when faced with these sorts of situations is to fiddle with it. The first call works. That's very good, it means you have some output to work with.
So try reversing the order so char_array2 is called first. What happens? Replace the arrays with literals? Does it work as expected? Call char_array1 twice. Is the second call still suppressed?

You gradually home in on what is causing the problem.

So why do you think SERCOM0_USART_Write and SERCOM1_USART_Write are the same thing?

Why do you refuse to post your code; note posting some one else's code does not count!

Code:

/*******************************************************************************
  SERCOM Universal Synchronous/Asynchrnous Receiver/Transmitter PLIB

  Company
    Microchip Technology Inc.

  File Name
    plib_sercom0_usart.h

  Summary
    USART peripheral library interface.

  Description
    This file defines the interface to the USART peripheral library. This
    library provides access to and control of the associated peripheral
    instance.

  Remarks:
    None.
*******************************************************************************/

/*******************************************************************************
* Copyright (C) 2018 Microchip Technology Inc. and its subsidiaries.
*
* Subject to your compliance with these terms, you may use Microchip software
* and any derivatives exclusively with Microchip products. It is your
* responsibility to comply with third party license terms applicable to your
* use of third party software (including open source software) that may
* accompany Microchip software.
*
* THIS SOFTWARE IS SUPPLIED BY MICROCHIP "AS IS". NO WARRANTIES, WHETHER
* EXPRESS, IMPLIED OR STATUTORY, APPLY TO THIS SOFTWARE, INCLUDING ANY IMPLIED
* WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY, AND FITNESS FOR A
* PARTICULAR PURPOSE.
*
* IN NO EVENT WILL MICROCHIP BE LIABLE FOR ANY INDIRECT, SPECIAL, PUNITIVE,
* INCIDENTAL OR CONSEQUENTIAL LOSS, DAMAGE, COST OR EXPENSE OF ANY KIND
* WHATSOEVER RELATED TO THE SOFTWARE, HOWEVER CAUSED, EVEN IF MICROCHIP HAS
* BEEN ADVISED OF THE POSSIBILITY OR THE DAMAGES ARE FORESEEABLE. TO THE
* FULLEST EXTENT ALLOWED BY LAW, MICROCHIP'S TOTAL LIABILITY ON ALL CLAIMS IN
* ANY WAY RELATED TO THIS SOFTWARE WILL NOT EXCEED THE AMOUNT OF FEES, IF ANY,
* THAT YOU HAVE PAID DIRECTLY TO MICROCHIP FOR THIS SOFTWARE.
*******************************************************************************/

#ifndef PLIB_SERCOM0_USART_H // Guards against multiple inclusion
#define PLIB_SERCOM0_USART_H

// *****************************************************************************
// *****************************************************************************
// Section: Included Files
// *****************************************************************************
// *****************************************************************************

#include "plib_sercom_usart_common.h"

// DOM-IGNORE-BEGIN
#ifdef __cplusplus // Provide C++ Compatibility

    extern "C" {

#endif
// DOM-IGNORE-END

// *****************************************************************************
// *****************************************************************************
// Section: Interface Routines
// *****************************************************************************
// *****************************************************************************

void SERCOM0_USART_Initialize( void );

bool SERCOM0_USART_SerialSetup( USART_SERIAL_SETUP * serialSetup, uint32_t clkFrequency );

void SERCOM0_USART_TransmitterEnable( void );

void SERCOM0_USART_TransmitterDisable( void );

bool SERCOM0_USART_Write( void *buffer, const size_t size );


bool SERCOM0_USART_WriteIsBusy( void );

size_t SERCOM0_USART_WriteCountGet( void );

void SERCOM0_USART_WriteCallbackRegister( SERCOM_USART_CALLBACK callback, uintptr_t context );


void SERCOM0_USART_ReceiverEnable( void );

void SERCOM0_USART_ReceiverDisable( void );

bool SERCOM0_USART_Read( void *buffer, const size_t size );

bool SERCOM0_USART_ReadIsBusy( void );

size_t SERCOM0_USART_ReadCountGet( void );

bool SERCOM0_USART_ReadAbort(void);

void SERCOM0_USART_ReadCallbackRegister( SERCOM_USART_CALLBACK callback, uintptr_t context );

USART_ERROR SERCOM0_USART_ErrorGet( void );

uint32_t SERCOM0_USART_FrequencyGet( void );

// DOM-IGNORE-BEGIN
#ifdef __cplusplus  // Provide C++ Compatibility

    }

#endif
// DOM-IGNORE-END

#endif //PLIB_SERCOM0_USART_H

Tim S.

So what does this do?

Code:

    SERCOM0_USART_Write("", 1);
    SERCOM0_USART_Write(&message[0], sizeof(message));

If you don't see message, then try replacing all the sizeof with strlen.
sizeof() will send a \0, whereas strlen() won't.