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Re: LF: PIC-based GPSDO with A/D converter / supported serial baudrates

To: [email protected], [email protected]
Subject: Re: LF: PIC-based GPSDO with A/D converter / supported serial baudrates ?
From: Andy Talbot <[email protected]>
Date: Wed, 17 Feb 2016 15:23:42 +0000
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I've just made some tests on the FTDI232 chip at high baud rates.

Using a custom routine written in  PowerBasic (CC) , I used that language's own interpretation and interface to the driver to pass arbitrary baud rates to the chip.   With the device set for 8 data,  1 stop bit and no parity, I repeatedly send the character 0x55 in a continuous loop.  This pattern of bits, if sent contiguously (characters are sent LSB first)  should therefore result in a square wave being generated at a frequency exactly equal to half the specified baud rate.

The FTDI232 data sheet states that baud rates are determined based on a 3MHz input to a divisor of (N + M/8, where N = 2 to 16384, plus two special cases on N = 0 and N = 1 for  3Meg and 1Meg rates respectively.   This setting is hidden from my application, and happens transparently based on the baud rate I specify beign passed to the driver via PowerBasic. 

The following results were obtained :

Requested         Frequency
Baud rate           Generated

1M                     500000
2M



On 12 February 2016 at 17:59, Wolfgang Büscher <[email protected]> wrote:
Thanks Andy. I wanted to keep it simple (but not necessarily stupid), by using available hardware. In my case, the dreadful (and, most likely, "faked") Prolific USB <-> RS232 adapter.
   

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