CC2511: How to initialize the power on system clock when using an external 24Mhz crystal oscillator and an external 32.768Khz crystal oscillator?

Alex Zhang

Part Number: CC2511

Hi，team:

The following is the code I initialized：

May I ask what is the configuration for using an external clock? I have a problem configuring the serial port baud rate to 115200 when using an external clock.

void OSC_Init(void)

{

CLKCON &= ~0x40;

while(SLEEP&0x40);

CLKCON &= ~0x41;

}

void Usart0_Init(void)

{

IEN0&=0x7f;

PERCFG&=0xfe;

P0SEL=0x0c; //P0.2-P0.3为外设，其余为通用io

P2DIR&= ~0XC0;

U0CSR=0x80;

U0UCR=0x00;

U0GCR=0x20;

U0GCR|=0x0c; //115200

U0BAUD=216;

UTX0IF=0;

URX0IF=0;

URX0IE=1;

EA=1;

}

over 2 years ago

0 Jake Pulliam over 2 years ago

TI__Expert 6520 points

Hi Alex,

I'm looking at this and will get back to you on Tuesday.

Jake

0 Jake Pulliam over 2 years ago in reply to Jake Pulliam

TI__Expert 6520 points

Alex,

CC2511 uses a 48 MHz Crystal:

Section 12.1.5 of the datasheet shows that the 48 MHz XTAL used with CC2511 is divided down to 24 MHz for the system clock. Using a 24 MHz clock the UART settings for 24 MHz can be found in Table 56:

BAUD_E = 12
BAUD_M = 59

So your settings above for BAUD_E = 12 and BAUD_M = 216 are incorrect and result in a baud rate of approximately 172851.

Jake

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CC2511: How to initialize the power on system clock when using an external 24Mhz crystal oscillator and an external 32.768Khz crystal oscillator?