LPC Microcontrollers中的主题 lpc54102 clock

lpc54102 clock

zhan8g — Tue, 27 Mar 2018 03:19:42 GMT

It is found that there is a problem in the LPC54102 chip. The internal IRC 12MHz clock is passed through EMI, but IRC has the problem of temperature drift. The long-term usage leads to UART communication rate deviation and can not communicate. Using 32K RTC PLL TO 12MHz, the system clock temperature drift problem has been solved, but there are more serious problems and very poor anti-interference. Why does this chip have such a problem?!!

Re: lpc54102 clock

zhan8g — Tue, 27 Mar 2018 09:22:31 GMT

Is this chip debug? Which one has a large and long-term use of LPC541XX chips，How to solve this problem？

Re: lpc54102 clock

zhan8g — Wed, 28 Mar 2018 00:47:35 GMT

Why？ NXP engineers don't reply to this problem？！！

Re: lpc54102 clock

Hui_Ma — Wed, 28 Mar 2018 09:14:48 GMT

Hi,

Below is the LPC5410x internal 12MHz IRC spec:

The IRC clock frequency drift with temperature is normal.

As you can see the full temperature range clock frequency accuracy within 3.5%.

The UART communication also allow communication clock accuracy tolerance, please check here for the detailed info.

I would recommend two ways to reduce the UART communication error rate:

1> reduce the UART communication baud rate;

2> using IRC Control register to trim the IRC with temperature change.

Wis it helps.

Have a great day,
Mike

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Re: lpc54102 clock

zhan8g — Wed, 28 Mar 2018 09:30:24 GMT

1>. UART baud rate is 9600bps, can start normal communication on the 2 day, then there will be communication failure. Useing oscilloscope test waveform, found that the system clock increased, causing the baud rate to become 9620bps.

Why? the IRC clock is just a rough measure, the measurement function returns 12000000, can be like the RTC PLL clock, fine measurement, return 12001280?

2>. How to trim , can it be explained in detail?

Thanks.

Re: lpc54102 clock

Hui_Ma — Fri, 30 Mar 2018 06:27:14 GMT

Hi,

In general, the internal IRC is really not very precise.

The IRC clock frequency could be changed with voltage and operation temperature modification.

We don't have LPC54102 IRC trim example.

While,there is an application note AN4020 about MPC5510 16MHz IRC clock calibration, the method is also suitable with LPC54102 IRC clock.

Wish it helps.

Have a great day,
Mike