Re: LPC2000 UART drops characters silently?

Started by Leon Heller July 19, 2006
----- Original Message -----
From: "jsm09a"
To:
Sent: Wednesday, July 19, 2006 6:43 PM
Subject: [lpc2000] Re: LPC2000 UART drops characters silently?
> --- In l..., "brendanmurphy37"
> wrote:
>
>> I've no doubt the results of your testing are valid. However, nobody
>> has been able to reproduce your "but drops characters at 19200 baud
>> and below" failure mode.
>
> Brendan,
>
> My compliments on your patience ;) One aspect that I haven't seen
> addressed is possible dependence on differences in realized baud rates.
>
> In these tests, the source and destination will be sync'd to different
> system clocks which may differ by an appreciable margin. I wonder if
> the conflicting results could be explained by differences in system
> clock rates.

Out of curiosity I just checked the oscillator on one of my old LPC2106
boards. Crystal is nominally 10 MHz, and I measured the frequency at
10.00005 MHz, there is a quite a lot of jitter on the next two digits. I
used a x10 scope probe to minimise any additional capacitance caused by the
measurement.

I used Philips recommended capacitor values on my board, I don't think that
everyone does. This could affect the frequency.

Leon

An Engineer's Guide to the LPC2100 Series