MSP430F5529: How to configure the max baud rate for USCI_A UART?

Eric Tian61

Other Parts Discussed in Thread: MSP430F5529

Hi,

I'm using MSP430F5529 launchpad and I need to transfer data to PC via usb cable as fast as possible.

When I was trying to use USCI_A1 (P4.4 & P4.5) UART and BRCLK=SMCLK=20MHz, the max baud rate I can get is 460800 via MSP Application UART1, but in the datasheet, the max baud rate is 1MHz. I tried this link:

to calculate the configuration values but it did't work for 921600 or 1M. So could anyone tell me what are the values of

clockPrescalar, firstModReg, secondModReg and overSampling to get a 1M baud rate from 20M BRCLK?

Thank you.

Regards,

Eric

over 10 years ago

0 Clemens Ladisch over 10 years ago

Guru 322010 points

To transfer data to the PC as fast as possible, you should not use the application UART, but send USB packets directly.

You can use either a virtual USB COM port (CDC), or a custom protocol.

0 zrno soli over 10 years ago

Guru 34843 points

Eric,

Transfer on LP is limited due to CDC / UART bridge software. However, MSP430F5529 UART can go over 1 Mbps.

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

There is calculator for UART setup

http://forum.43oh.com/topic/2640-uart-configurator/

0 Lukasz over 10 years ago

Mastermind 7595 points

The max baudrate is BRCLK/3 bps
Recivind data on PC you must use virtual USB COM.

0 Eric Tian61 over 10 years ago in reply to Clemens Ladisch

Intellectual 890 points

Hi Clemens,

Could you please tell me how to change the baud rate of the virtual USB COM port for the SimpleUsbBackchannel project? It works fine with 28800 but I cannot find the codes to configure the baud rate. Thanks.
Regards,
Eric

0 Clemens Ladisch over 10 years ago in reply to Eric Tian61

Guru 322010 points

That example uses both a virtual port (CDC) and a real UART (the backchannel), and the baud rate applies only to the UART. A better example for you would be C6_SendDataBackground.

0 Eric Tian61 over 10 years ago in reply to Clemens Ladisch

Intellectual 890 points

Found it, thanks, I am reading it.
Regards,
Eric

0 Eric Tian61 over 10 years ago in reply to zrno soli

Intellectual 890 points

Hi zrno,
So the CDC / UART bridge software limits the baud rate From LP to PC via USB cable so it can not go over 1Mbps? If I connect UCA1RXD to UCA1TXD over 100 ohm resistor, I can get 1Mbps?
Eric

0 Eric Tian61 over 10 years ago in reply to Lukasz

Intellectual 890 points

BRCLK = 20MHz so max baudrate>6Mbps? Can uart go so fast?

0 zrno soli over 10 years ago in reply to Eric Tian61

Guru 34843 points

Eric Tian61 said:
Hi zrno,
So the CDC / UART bridge software limits the baud rate From LP to PC via USB cable so it can not go over 1Mbps? If I connect UCA1RXD to UCA1TXD over 100 ohm resistor, I can get 1Mbps?
Eric

I don't work with TI LP's and don't know about FET CDC/UART software limitation. My flasher with dual CDC / UART bridge can go over 1 Mbps.

http://forum.43oh.com/topic/2972-sbw-msp430f550x-based-programmer/?p=53730

Picture is not visible for 43oh non-members, it is attached here.

If you need high speed UART transfer, run MSP430 on 24 MHz by XT2, and use dedicated bridge chip / cable like PL2303HXD. MSP430F5529 has USB hardware module that can go with CDC / Bulk up to 1 MByte/s, and PC side with CDC is the same like for UART.

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MSP430F5529: How to configure the max baud rate for USCI_A UART?