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CCS/MSP430F5529: Does the MSP430F5529 support 921600 UART BAUD RATE ?

Haithem Rahmouni
Intellectual 605 points
Part Number: MSP430F5529
Other Parts Discussed in Thread: MSP-FET

Tool/software: Code Composer Studio

Dear TI Support Team,

I want to communicate with MSP430F5529 through the UART with baud rate 921600.

Is it possible?  if yes, what is the correct configuration?

If not, what's the maximum baudrate ?

regards,
Haithem.

  • 0
    Guru 34453 points

    BTW, 5529 has USB hardware module, and (CDC / bulk) transfer can go up to 1 Mbyte/s.

    Depend on MCLK and UCA source clock, UART can go up to 6 Mbps.

    http://forum.43oh.com/topic/3413-msp430-uart-benchmark/

    There are many online BR calculators for msp, here is mine for offline setup...

    MSP430UartCalc.rar

  • 0
    Guru 298950 points

    As shown in the datasheet, the maximum baud rate is 1 MHz.

    The UART's clock source must be at least three times the baud rate (or at least sixteen times in oversampling mode). However, the USCI baud-rate generator tends to work best when it can divide the clock source by a large divisor, so you should make the clock source as fast as possible. How to calculate the resulting errors is shown in section 36.3.9 of the User's Guide; or just use the USCI UART Calculator. After playing with some valuest, it appears that 24 MHz is a good clock source.

    Please note that the DCO is not very accurate and introduces jitter; you need to take the clock source directly from a 24 MHz crystal (oscillator).

  • 0 in reply to Clemens Ladisch
    Intellectual 605 points

    Dear Clemens,

    Thank you for your reactivity!

    Could you please help me to correctly configure UART registers and connect the BRsclk source clock directly to the external crystal source?

    Note that in my board I have to crystal one 24MHZ ( ABM3B-24.000MHZ-10-1-U-T ) the second is 32.768KHZ,I need to communicate with an external peripheric(not a host) through  high-speed UART 

    Regards,

    Haithem.

  • 0 in reply to Haithem Rahmouni
    Intellectual 605 points

    I have just tested my board with configuration as below, but I haven't received a good/correct data !

    with 115200 : test OK  / for baudrate (230400, 460800,921600 ) test NOK missed and wrong data.

    Test condition : My board connected to PC through EZ-FET with UART conexions ( MCU(MSP430 <--> EZ-FET UART Bridge <---> PC)

    UART Configuration :

    Any suggestion or advice, please?!

  • 0 in reply to Haithem Rahmouni
    Guru 34453 points

    Here is setup for 1 Mbps, with 24 MHz XT2 MCLK as UART clock source. 24 / 18h = 24 / 24 = 1 Mbps (no error).


    I guess that eZ-FET Lite USB / UART bridge is limited to some fixed baudrate values, like MSP-FET.


    There is no problem with 2xx/5xx device UART on higher rates. Here you can see my dual bridge with 2xx device in action on 4 Mbps.

    		mov.w #WDTPW + WDTHOLD, &WDTCTL

		mov.b &CALBC1_16MHZ, &BCSCTL1
		mov.b &CALDCO_16MHZ, &DCOCTL
        
		bis.b #UCSWRST, &UCA0CTL1

		bis.b #(BIT5 + BIT4), &P3SEL	; P3.4/P3.5 = TXD/RXD
		bis.b #UCSSEL_2, &UCA0CTL1	; SMCLK

		; 16000000 Hz  4000000 bps
		mov.b #004h, &UCA0BR0
		mov.b #000h, &UCA0BR1
		bis.b #(UCBRS_0 + UCBRF_0), &UCA0MCTL

		bic.b #UCSWRST, &UCA0CTL1

		mov.w #70, R14
		mov.b #32, R15
		
Loop		bit.b #UCA0TXIFG, &IFG2
		jnc Loop
		mov.b R15, &UCA0TXBUF
		
		add.b #1, R15
		cmp.b #127, R15
		jne Loop
		
		mov.b #32, R15
		sub.w #1, R14
		jnz Loop

  • 0 in reply to Haithem Rahmouni
    Guru 298950 points
    How did you configure ACLK?

    The eZ-FET uses a 4 MHz resonator, so it's likely that the problem is the backchannel UART.

    What is the actual problem you're trying to solve? Do you actually intend to use the backchannel UART, or some other device?
  • 0 in reply to Clemens Ladisch
    Intellectual 605 points
    Thank you for your help !

    Problem resolved, it work perfectly with the shown configuration at 24Mhz.

    The problem was the EZ-Fet that I used as UART to USB adaptator to test my UART communication. I changed it with an FTDI adaptator.
  • 0 in reply to Haithem Rahmouni
    Intellectual 605 points
    Now I have a problem with reciving data , when I send a packet of bytes from my PC to MCU I remarq that I only got the last byte of the packet !
    Note that this test is work fine with ( 115200, 230400, 460800 ) but I have the problem only when Baudrate is 921600.

    Any Help please ?
  • 0 in reply to Haithem Rahmouni
    Guru 298950 points
    Apparently, your code does not react fast enough to the received bytes.
  • 0 in reply to Haithem Rahmouni
    Guru 298950 points

    When the CPU runs at 24 MHz, and the baud rate is about 1 MHz, you have 24 cycles to handle a byte.

    That code can be optimized. Read RXBUF only once and put it into a local variable. Don't try to do all error checking in the interrupt handler; when you get a START_DATA_HEADER, just read seven bytes into the buffer, and check in the main loop.

    It might be a better idea to use DMA to read a block of bytes from the UART.

  • 0 in reply to Clemens Ladisch
    Intellectual 605 points
    I will try with your recommendation and return the feedback.

    Could you please tell me how I can use the DMA in my case ?

    Thank you !
  • 0 in reply to Haithem Rahmouni
    Guru 298950 points
    That depends on how your protocol works.

    To understand the DMA module, read the User's Guide and the example programs.
  • 0 in reply to Haithem Rahmouni
    Guru 34453 points

    Haithem Rahmouni said:

    I am using the RX interruption, the following code work fine with ( 115200, 230400, 460800 ) but not with 921600 :

    Could you please tell me what type of problem we can appear in fast mode ?

    You can do it without DMA. My dual bridge code receiving at 4 Mbps from 2 ports, and it is done without DMA. From my experience, DMA in this case make things more complicated, not faster.

    Just store received bytes in circular buffer inside ISR. Other processing (analyzing circular buffer contest) can be done outside ISR.

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