Uart Rx and DMA - need little help

[lololafripouille]

Hello

I'm trying to implement Uart Rx via DMA.
I don't understand very well the science behind that but I need DMA on Uart Rx.

I read example for Microchip but I don't understand the way they allocate buffer to DMA.

I have this simple code that doesn't work :

Code: Select all

//******************************************************************************
//  Allocate one buffer for DMA transfers
//*****************************************************************************/
unsigned int Uart1_Rx_Buffer[25];


/*******************************************************************************
* Function InitMCU()
* ------------------------------------------------------------------------------
* Overview: Function Initialize controller
* Input: Nothing
* Output: Nothing
*******************************************************************************/

void InitMCU()
{                                                       
   ANSELB = 0b0000000000000000;                                                
   ANSELC = 0b0000000000000000;                                                
   ANSELD = 0b0000000000000000;                                                
   ANSELE = 0b0000000000000000;                                                 
   ANSELG = 0b0000000000000000;                                                

   ODCD4_bit = 1;
   CNPUD4_bit=1;                                                               
   


   //PLLFBD = 74;                                                               // M=76   = 140Mhz
   PLLFBD = 41;                                                                 // M=43   = 80 Mhz
   CLKDIVbits.PLLPOST = 0;                                                      // N1=2
   CLKDIVbits.PLLPRE = 0;                                                       // N2=2
   OSCTUN = 0;                                                                  // Tune FRC oscillator, if FRC is used
   RCONbits.SWDTEN = 0;

   while (OSCCONbits.NOSC != 0b001);                                            // Wait for Clock switch to occur
   while (OSCCONbits.LOCK != 1) {};                                             // Wait for PLL to lock

                                                            
   U1STAbits.URXISEL  = 0;                                                      
   INTCON1bits.NSTDIS = 1;                                                     
   IFS0bits.U1RXIF    = 0;                                                    
   //IEC0bits.U1RXIE = 1;                                                     
   //IPC2bits.U1RXIP = 7;
   UART1_Init_Advanced(100000,                                              
                       _UART_8BIT_EVENPARITY,
                       _UART_TWO_STOPBITS,
                       _UART_HI_SPEED);
   U1MODEbits.URXINV=1;                                                         

   Unlock_IOLOCK();
   PPS_Mapping( 97, _INPUT,  _U1RX );
   
   PPS_Mapping(68, _INPUT , _INT1 );
   
   //Lock_IOLOCK();
   
   delay_ms(100);                                                             

   DEBUG_Direction = OUTPUT;                                                   
   DEBUG = 0;
   
   OSCILLO_Direction = OUTPUT;
   OSCILLO = 0;

   LancPin_Direction = INPUT;

}

void cfgDma1UartRx()
{
//******************************************************************************
//  Associate DMA Channel 1 with UART Rx
//*****************************************************************************/
   DMA1REQ = 0x000B;                                                            // Select UART1 Receiver
   DMA1PAD = &U1RXREG;

   DMA1CONbits.AMODE = 0;
   DMA1CONbits.MODE  = 1;                                                       //One-Shot, Ping-Pong modes are disabled
   DMA1CONbits.DIR   = 0;
   DMA1CONbits.SIZE  = 1;
   DMA1CNT           = 24;                                                      // 25 DMA requests
        
   DMA1STAL = &Uart1_Rx_Buffer;
   DMA1STAH = &Uart1_Rx_Buffer;

//******************************************************************************
// Enable DMA Interrupts
//*****************************************************************************/
   IFS0bits.DMA1IF  = 0;                                                        // Clear DMA interrupt
   IEC0bits.DMA1IE  = 1;                                                        // Enable DMA interrupt

//******************************************************************************
//  Enable DMA Channel 1 to receive UART data
//*****************************************************************************/
   DMA1CONbits.CHEN = 1;                                                        // Enable DMA Channel
}

void DMA1_Interrupt() iv IVT_ADDR_DMA1INTERRUPT ics ICS_AUTO
{
   DEBUG = 1;
   delay_ms(2);
   
   IFS0bits.DMA1IF = 0;                                                         // Clear the DMA1 Interrupt Flag
}


void main()
{
   InitMCU();
   cfgDma1UartRx();
   INTCON2bits.GIE = 1;                                                         // global interrupt enable

   while(1)
   {
      
      if(U1STA.OERR == 1)                                                       // Must clear the overrun error to keep UART receiving
      {                                                                         
         U1STA.OERR = 0;
         continue;
      }

      if(U1STAbits.FERR == 1)
      {
         U1STA.FERR = 0;
         continue;
      }
      
      DEBUG = 0;
   }
}

I think I have a problem with the buffer declaration and the DMA1STAL/DMA1STAH register.
Is it possible to have some help ?

How can I configure this to have a working setup ?
Thank you for your help

[dusan.poluga]

Hi,

What micro controller are you using ?

Regards,

[lololafripouille]

Hello,

It's a dsPIC33EP512MC806.

[dusan.poluga]

Hi,

I am sorry for the inconvenience.
We currently do not have a DMA example written for this micro controller.
I would strongly suggest you get more familiar about Direct memory accessing before you go into the topic.
Also some useful reading material and the work principal of the DMA can be found in the specified micro controller datasheet.

Regards,