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Timer UART vs USCI UART

Raju Purohit

Prodigy 110 points

Other Parts Discussed in Thread: MSP430G2553

Hello all,

I am a beginner and using MSP430 launchpad having MSP430G2553. Till now I have got along with interrupts, timers and ADCs and I am able to read temperature in the registers in CCS. Obviously my next worry is to use UART communication to transmit internal temperature sensor reading to my computer.

I want to ask what is the difference between Timer UART and USCI UART? In the pre-installed code provided by TI in MSP430G2553, they have used Timer UART while they could have used USCI UART module, right? USCI UART seems to be much simpler to understand and implement. Whats the catch?

Thank you in advance.

over 13 years ago

0 Alan over 13 years ago

Expert 2260 points

No catch use the USCI if possible.

The older revisions of the launchpad would have required some hardware changes to support USCI UART - one the newer ones I believe you can just alter the orientation of the TX RX jumpers to switch the UART over to the USCI pins.

I assume they also favoured the Timer A usage as I presume the other chips which were previously provided did not have a USCI UART.

0 Raju Purohit over 13 years ago in reply to Alan

Prodigy 110 points

Thanks Alan. I wrote a small program to transmit alphabets from a to z using USCI UART. But I am not able to get any output at the HyperTerminal. Can you or anyone please check if there might be error? (I don't even know if I should be posting this here). I have properly set the settings (Baud rate, etc) in HyperTerminal.

#include "msp430g2553.h"
#define RED BIT0

void main(void)
{
unsigned int i=0;
WDTCTL = WDTPW + WDTHOLD; // Stop WDT

P1DIR = 0xFF; // All P1.x outputs
P1OUT = 0; // All P1.x reset

P1SEL = BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD
P1SEL2= BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD

BCSCTL1 = CALBC1_1MHZ; // Set DCO
DCOCTL = CALDCO_1MHZ;

UCA0CTL1 |= UCSSEL_2; // CLK = SMCLK
UCA0BR0 = 104; // 1MHz/9600 =104
UCA0BR1 = 0x00; //
UCA0MCTL = UCBRS1 + UCBRS0; // Modulation UCBRSx = 3
UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
// No interrupts

for (i=97;i<123;i++)
{
while (!(IFG2&UCA0TXIFG)); // USCI_A0 TX buffer ready?
UCA0TXBUF = i;
P1OUT ^= RED; // Red LED toggles everytime a byte is sent
_delay_cycles(100000); // Observe LED toggling
}
}

Should I have done something with jumper connections?

Thanks

0 Alan over 13 years ago in reply to Raju Purohit

Expert 2260 points

I am afraid I cannot be a whole lot of use here as a hardware UART isn't something I have dabbled with.

However I know that the hardware UART has RXD = 1.1 and TXD = 1.2 however the Timer A example - and the connections to the USB - have TXD = 1.1 and RXD = 1.2 so you need to interchange these connections.

On the rev 1.5 board:

Jumpers 4 and 5 connect the UART interface of the emulator to the target device pins P1.1 and P1.2. The
direction of the UART signal lines can be selected by the orientation of the attached jumpers. In horizontal
orientation, the jumpers connect TXD to P1.1 and RXD to P1.2, as they are used for the software UART
communication on the demo application (see Section 3.2). In vertical orientation, the jumpers connect the
TXD signal to P1.2 and the RXD signal to P1.1, as required for the MSP430G2553 USCI.

www.ti.com/lit/ug/slau318b/slau318b.pdf

You should be able to check the box to see if you have the rev 1.5 board, but it should be easily identified as it came with male headers attached ( as well as with a 2553 so I am assuming you have this model)

However if you have an older LP you'll need to do something like this:

http://www.43oh.com/2011/10/dongle-swaps-serial-lines-on-the-launchpad/

0 Alan over 13 years ago in reply to Raju Purohit

Expert 2260 points

With regards to HyperTerminal its been a while since I have used it. I assume a connection has been made on the correct COM port - its usually distinctly labelled?

The baud rate will be 9600. Though even if it is wrong you should still be seeing gibberish coming through at the terminal.

0 Raju Purohit over 13 years ago in reply to Alan

Prodigy 110 points

Alan,

That worked. Thanks a ton. That was so simple.

By the way, why did TI change the configuration when they were following one format all these years? Anyways, never mind, and thanks again.

0 chinmay deshpande over 12 years ago in reply to Alan

Prodigy 150 points

very helpful suggestion... and saved lot of time

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