NHD‐0220D3Z‐NSW‐BBW Default Baud Rate

David VB

• February 05, 2025 11:52

Hi,

There is a confusion in the datasheet for this display:
- The text says the default baud rate is 9600
- the example code sets the baud rate at 2400

Which one is the default baud rate ?

Thanks

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• 

  Engineering Support

  Community moderator

  • February 05, 2025 15:24

  Hi David,

  Thanks for your post.  The default baud rate of this display should be 9600, but the baud rate can be changed using the "Change RS-232 BAUD rate" command.  This can be verified by sending the "Display RS-232 BAUD rate" command or by placing the display in self-test mode by populating R1 and R2 with 0Ω resistors.  Can you share which example code you are referring to?

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  David VB

  • February 06, 2025 10:02
  • Edited

  Hi,
  
  Thank you for your quick answer.
  
  In the datasheet of the display, there is a link to an example code:
  http://www.newhavendisplay.com/app_notes/Serial_LCD.txt
  
  And in this example, the code to initialize the USART of the "Master" PIC (PIC18F2321) is the following:

  void init_rs232(void)
  {
  	TXSTA = 0x26;			// rs232 transmit status register
  	RCSTA = 0x80;			// serial port enable
  	BAUDCTL = 0x08;			// BRG16 = 1;
  	SPBRG = 207;
  	SPBRGH = 0;
  }

  
  Which, if I'm not mistaken, sets the baud rate to 2400 baud (for a clock speed of 8 MHz, as stated on the beginning of the example)

  OSCCON |= 0x73;			// internal RC, 8MHz
  

  (Which, BTW, should (I think) be OSCCON = 0x73)

  If this code is used for the very first time with a display (set by default at 9600 baud), this will not work.  Therefore the confusion....
  
  If you do agree, may I suggest this example code being adapted ?  (SPBRG should be set to 51)
  
  Thanks a lot,
  
  Have a nice day,
  
  David.
  
  
  
  
  

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  Engineering Support

  Community moderator

  • February 06, 2025 18:30

  Hi David,

  Thanks for clarifying.  I do believe you're right and I suspect the baud rate may have been mistakenly calculated for 16-bit mode rather than 8-bit mode.  I will see to have this corrected in the example code.  If I'm not mistaken, I believe setting SPBRG = 51 should correctly set the baud rate to 9600.

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  David VB

  • February 06, 2025 18:37
  • Edited

  Thank you for your interest :-)
  Glad I could help!

  
  Kind regards,

  David

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