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Tx using the C8051F30x

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Author	Topic: Tx using the C8051F30x
DavidGMarcus New Member	posted July 28, 2010 10:27 AM I am using the C8051F30x and I am trying to Transmit for right now a character "A" to the computer.(Basic I know) When using the SI labs dev board for the C8051F30x I set my baud rate to 9600 and the Character that I write out is the character I receive. However when I change the baud rate to 4800 the character that I write out is not what i receive. I receiver a U with 2 dots above it. I then compared the signals of the Character A from the computer a 4800 Baud to that of a character A coming out of the C8051F30x. They are the same signal except the one coming from the computer is much more compact.(Computer's A=4ms C8051F30x's A= 11ms) Why is my signal almost 3 times longer than the computers? Below is my intialiation for the UART after i define the Baud to be 4800: void UART0_Init (void) { SCON0 = 0x10; // SCON0: 8-bit variable bit rate // level of STOP bit is ignored // RX enabled // ninth bits are zeros // clear RI0 and TI0 bits if (SYSCLK/BAUDRATE/2/256 < 1) { TH1 = -(SYSCLK/BAUDRATE/2); CKCON \|= 0x10; // T1M = 1; SCA1:0 = xx } else if (SYSCLK/BAUDRATE/2/256 < 4) { TH1 = -(SYSCLK/BAUDRATE/2/4); CKCON \|= 0x01; // T1M = 0; SCA1:0 = 01 CKCON &= ~0x12; } else if (SYSCLK/BAUDRATE/2/256 < 12) { TH1 = -(SYSCLK/BAUDRATE/2/12); CKCON &= ~0x13; // T1M = 0; SCA1:0 = 00 } else { TH1 = -(SYSCLK/BAUDRATE/2/48); CKCON \|= 0x02; // T1M = 0; SCA1:0 = 10 CKCON &= ~0x11; } TL1 = 0xFF; // Set Timer1 to overflow immediately TMOD \|= 0x20; // TMOD: timer 1 in 8-bit autoreload TMOD &= ~0xD0; // mode TR1 = 1; // START Timer1 TI0 = 1; // Indicate TX0 ready IP: Logged
erikm Member	posted July 28, 2010 11:07 AM I then compared the signals of the Character A from the computer a 4800 Baud to that of a character A coming out of the C8051F30x. They are the same signal except the one coming from the computer is much more compact. the baudrate setting is wrong. 4800 baud ~ 480 chars ~ 20ms/char. Note that config, while excellent, is not error free, use the formula in the datasheet A better way is to constantly transmit uppercase U and measure the bit time. Erik [This message has been edited by erikm (edited July 28, 2010).] IP: Logged
worknhard9062 Member	posted July 28, 2010 12:30 PM 4800 baud ~ 480 chars ~ 20ms/char. Of course you meant 2ms/char. ------------------ Regards, Steve C. IP: Logged
erikm Member	posted July 28, 2010 01:27 PM ah, that basted decimal point, it often get me in trouble Erik IP: Logged

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