[fpc-pascal] Re: (OT) Re: How to use UART of ARM platforms (e.g. Raspberry Pi ) through free Pascal?

[Mark Morgan Lloyd]

Luca Olivetti wrote:
> Al 04/07/13 17:24, En/na Mark Morgan Lloyd ha escrit:
> 
>> In any event, my experience is that USB->serial converters are very poor
>> for anything that involves accurate timing, and I suspect that
>> controlling a 485 transceiver in conjunction with one would be
>> problematic.
> 
> Not if the converter manages the rx/tx switching all by itself
> 
>> I think I asked FTDI about this a couple of years ago, and
>> was told that their hardware had facilities that would help but
>> exploiting them would take a non-standard driver.
> 
> The ones I used worked with the standard driver: send something, it
> automatically enables the transmitter, after the last bit has been
> transmitted it goes in high impedance mode ready for listening/receiving.

Yes, but I was considering the case of using an off-the-shelf USB->RS232 
device, followed by an RS232->RS485 converter (OP's note of this morning).

A couple of years ago I was reverse-engineering the protocol used by 
some HP protocol analysers (so that I could use them for 
reverse-engineering protocols...) and my initial hack used a couple of 
standard USB devices. Unless I slowed the data stream right down (300 
Baud) the driver buffering messed things up to the extent that I 
couldn't determine where there were gaps, let alone measure them so I 
could work out what the timeouts were.

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]