AAAReadme.txt

gistfile1.txt

I came across this article a while back but hadn't had a chance to play with it.

http://www.msp430launchpad.com/2010/08/using-usi-as-uart.html

Armed with a Sparkfun FTDI FT232R breakout board, linux, msp430-gcc and an msp430g2452
I put the code below on it and was able to use putty connected @ 2000000 bps to send
data to my linux box.  The bit duration is a blazing 500ns wow!

Hmm .. interesting

usiserialtest.c

//******************************************************************************
//  
//  Description: Continuously sends a counter value over the USI in SPI which
//		 acting as if it were a UART. The sample circuit connects an
//		 FTDI breakout board to the transmit line and reads. The baud
//		 rate is determined by the USI speed, which in this case is
//		 2000000 baud (DCO = 16MHz).
//
//  Nicholas J. Conn
//  08-04-2010
//  Built with CCS Version: 4.1.3
//  09-15-2011 Rick Kimball changed to 2MBit and msp430g2452
//  
//******************************************************************************

#include  "msp430.h"

// Function Definitions
void transmit(unsigned int);

int main( void )
{
     WDTCTL = WDTPW + WDTHOLD;             // Stop watchdog timer
  
     /* use precalibrated 16MHz value */
     DCOCTL = 0;
     BCSCTL1 = CALBC1_16MHZ;
     DCOCTL = CALDCO_16MHZ;

     //****************************
     //   Set up USI - LSB first
     //****************************
     USICTL0 |= USIPE6 + USIMST + USILSB + USIOE;	// Enable Output, SPI master, LSB first
     USICTL1 |= USIIE;   				// Counter interrupt, flag remains set
     USICKCTL = USIDIV_3 | USISSEL_3;       		// Use SMCLK/8
  
     USICTL0 &= ~USISWRST;               		// USI released for operation
  
     //*******************************************************
     //   Set initial program varibles and start peripherals
     //*******************************************************
     unsigned int i = 0;
     unsigned int TXData;
     const char *buffer = "Hello world 2000k baud\r\n";
     while(1)
     {
	  for(i=0; buffer[i] ; i++ ) {
//	       transmit(0x55);
	       transmit(buffer[i]);
	  }
     }
} 

// Transmits one byte (TXData) using the USI as a UART
void transmit( unsigned int TXData )
{    
     //**********************************************
     //   Send a byte on the USI as if it were UART
     //**********************************************
     TXData = TXData << 1;             // Add start bit
     TXData |= 0xFE00;                 // Add stop bit
  
     while (!(USIIFG & USICTL1)); 	// Wait if USI is busy
     USISR = TXData;    		// Sets word to be sent
     USICNT = USI16B + 10;           	// 16 bit mode, sends 10 bits
}