MSP-EXP430FR5994: Setting Baud Rate to 115200 for 8MHz DCO CLK

Kirushigan Parathan

Hi, I am wondering what the config is to set the baud rate to 115200, I get 9600 working fine however when I switch it to 115200 it doesn't work. Is there something incorrect with my configurations.

UCA1CTLW0 |= UCSSEL__SMCLK; // CLK = SMCLK

UCA1BR0 = 4;
UCA1BR1 = 0;
UCA1MCTLW |= UCOS16 | UCBRF_2 | 0x49

over 4 years ago

0 EmbeddedMike over 4 years ago

Expert 1260 points

all the information you need is in section 30.3.10 of the user guide:

0 Kirushigan Parathan over 4 years ago in reply to EmbeddedMike

Expert 1180 points

so i did use this table however ,my value exceeds whats on the table. From the example code on TI

// Baud Rate calculation
// 8000000/(16*9600) = 52.083
// Fractional portion = 0.083
// User's Guide Table 21-4: UCBRSx = 0x04
// UCBRFx = int ( (52.083-52)*16) = 1
UCA3BRW = 52; // 8000000/16/9600
UCA3MCTLW |= UCOS16 | UCBRF_1 | 0x4900;
UCA3CTLW0 &= ~UCSWRST; // Initialize eUSCI
UCA3IE |= UCRXIE; // Enable USCI_A3 RX interrupt

I dont understand where the 0x04 goes into. I understand how they get 0x4900 ( from the table (0.083*16) - 1 = 0. 0.328, which corresponds to 0x4900). for my calculations 8000000/16/115200 = 4.34.

0.34* 16 - 1 = 4.44, is what im getting as the fractional portion of N

0 EmbeddedMike over 4 years ago in reply to Kirushigan Parathan

Expert 1260 points

Did you try these settings yet?

0 Lixin Chen1 over 4 years ago in reply to EmbeddedMike

TI__Expert 7015 points

Hi, Kirushigan,

Do you have reset UCSWRST before configure the eUSCI registers? You can try following configurations to see if it works.

// Configure USCI_A0 for UART mode
UCA0CTLW0 = UCSWRST; // Put eUSCI in reset
UCA0CTL1 |= UCSSEL__SMCLK; // BRCLK = SMCLK
UCA0BR0 = 4; // (8000000/115200)/16 = 4.34
UCA0MCTLW = 0x5551;

UCA0BR1 = 0;
UCA0CTL1 &= ~UCSWRST; // release from reset
UCA0IE |= UCRXIE; // Enable USCI_A0 RX interrupt

Thanks,

Lixin

0 Lixin Chen1 over 4 years ago in reply to Lixin Chen1

TI__Expert 7015 points

Hi, Kirushigan,

Do you have more questions for this topic?

Thanks,

Lixin

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MSP-EXP430FR5994: Setting Baud Rate to 115200 for 8MHz DCO CLK