uart dma stops sending data

Hi Rajesh,

We have tested our BSP example (driver-based) with your configuration (at a baud rate of 921600), and it is functioning correctly on our end.

We suspect the clock configuration may causing the issue, as the code works correctly at a baud rate of 460800. So, could you please share us your UART_CLK Register value? and please let us know if you are encountering any errors or exceptions.

Additionally, please check the following Ezone thread, which contains BareMetal code for the UART Tx DMA in the ADSP-SC594 that may be helpful for you:
https://ez.analog.com/dsp/sharc-processors/f/q-a/581346/sc59x-uart-tx-dma

Regards,
Nandini.C

Hi Nandini, thanks for response. 

I have referred the link above. and the codes are made similar. here is my UART baud rate initialization. 

this is done once before interrupt is enabled. and uart write is done in 1ms ISR. 
when called in 1ms ISR, the uart sends data for some time and then the code crashes after running for 4-5 minutes. 

#define M_CCLK				(450e6)
/*processor SCLK0 clock frequency*/
#define M_SCLK0				M_CCLK/4 //(112.5e6)

void InitUartDsp(void)
{
    T_U32  baudrate = M_CLEAR;

	/*~ GPSB-SDD-FNC-7536 ~*/
	/* Enable un-secure transaction */
	*pREG_SPU0_SECUREP31 = M_THREE; /* UART 0*/
	*pREG_SPU0_SECUREP83 = M_THREE; /*UART0 TX DMA20*/
	*pREG_SPU0_SECUREP82 = M_THREE; /*UART0 RX DMA21*/

	baudrate = M_SCLK0 / 460800;

	*pREG_UART0_CLK = (1u << 31) | baudrate  ; // edbo =1 

	/* Clear the interrupt mask*/
	*pREG_UART0_IMSK_SET = M_ZERO;

	/* Enable the UART0 and choose the word length 8 with no parity */
	*pREG_UART0_CTL = ENUM_UART_CTL_CLK_EN | ENUM_UART_CTL_WL8BITS;


}

Hi team

please respond to this and let me know if you need more info

Hi Rajesh,

We are currently replicating the issue on our EZkit. In the meantime, could you please confirm if you have tested at any lower baud rates, and if so, whether it worked?

Regards,
Nandini.C

hi Nandini

we needed to send about 500 bytes of data every 1ms, so we were trying for higher baud rate. 
just curious, what is relation of DMA with baud rates.  UART protocol will get address to send and baud rate, DMA should place data on UART lines. 

is there any timing constraint on that? is there any timing diagram of how much DMA will take to finish the xcount data move? 

Hi Rajesh,

Sorry for the delay in getting back to you.

There are no such constraints. We requested your confirmation in order to isolate whether the issue is related to the hardware design.

Please refer to the attached project, which works correctly on the ADSP-SC589 Ezkit at both 460800 and 921600 baud rates.

UART_TX_All_Cores_SC589_Core0.zip

Please take this as a reference and modify it as per your requirement.

Regards,
Nandini.C

Nandini 

the project attached does not replicate my issue. the UART operation is in main and not in ISR. 

issue appears in 1ms ISR.

in real time operation, giving delay of 200000 in between each byte write to UART is a lot of delay. 

in project shared there is no DMA operation. 

and there is no need for UART1 TX interrupt handler

please consider the fact, that in 1ms ISR there are other processing to be done. example 5 FFT operation. in 1ms. UART should not take so much of processor clocks. 

please reconsider the approach. 

Hi Nandini 

I tried the way it is done in the sample code 

but this line of code did not compile in my ADSP21583 processor. 

char iUART0TxBuffer[MESSAGE_LENGTH] __attribute__((section(".l2_uncached_data"))); 

hence i tried like this 

section ("seg_l2_uncached") volatile unsigned char     tx_msg_buffer[512]; 

There is improvement.

At 460800 baud, 

• the code does not crash.
• and it sends more number of bytes 
• but i need to send some additional bytes before the actual data one time to start the data transmission on UART. (not sure why ? )
• Also, in code shared above only 36 bytes are sent.  Does it work on your system if you send nearly 400-500 bytes ? 

At 912600 baud

• The bytes are getting corrupted. 

what could be missing? 

Hi Rajesh,

Initially, we used 36 bytes in the example because that was the original transfer size you provided.

Regarding your updated requirement of transferring 400 or 500 bytes, it appears that achieving the transfer within 1 millisecond is not possible at the current baud rates.

At 921,600 baud, the baud rate represents 921,600 bits per second. You can send approximately 921 bits in 1 millisecond. Similarly, at 460,800 baud, you can send approximately 460 bits in 1 millisecond.

However, since you're trying to transfer 3,200 bits (for 400 bytes), this exceeds the 1 millisecond window at both baud rates, making the transfer unfeasible within that timeframe. Therefore, you need to adjust either the timing or the amount of data to be transferred.

Regards,
Nandini.C