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My setup is:

  • LPC1225FBD48/321
  • ext crystal: 16MHZ
  • PLL: MSEL=6, PSEL=2
  • UART0: CLKDIV=250 DL=1 DIVADDVAL=1 MULVAL=4

PLL gives mainclk=96MHz ; PCLK for UART is: 96MHz/250=384kHz ; Bit rate: 384kHz/(16x1x1.25)=19200

And it works, but only when LPC transmits. When LPC receives a character, it reports 2 characters received and sometimes framing error. Similar problem for other bit rates. At lower rates, like 2400, LPC reports single character received and sometimes framing error, but received character is not the same as I sent. It looks like Tx and Rx are using different clocks.

The UART works well when using bootloader with Flash Magic.

Has anyone encountered such a problem?

Jerry Xia
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1 Answers1

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I finally found a solution. After setting CLKDIV = 50 and DL = 5, the UART became fully functional. While the documentation did not prohibit the previous set of parameters and both sets should give the same result, only the latter allows two-way communication.

Jerry Xia
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