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

[Mark Morgan Lloyd]

Lukasz Sokol wrote:
> On 04/07/2013 12:03, Michael Schnell wrote:
>> On 07/04/2013 12:52 PM, Lukasz Sokol wrote:
>>> For RS485 adaptation, use a MAX232 like chip (to convert +-12 to
>>> ttl) and then a RS485 transceiver chip;
>> If you want to create hardware anyway, better use a PIC24 (pr PIC32)
>> chip with USB plus a RS485 tranceiver chip. So you get rid of the "
>> ATEN usb-to-serial cable (UC-232A)" and you have both sides of USB
>> under your control so that you can do the USB procedure you want.
>>
> +1 if OP wants to create his own hw and sw for that purpose
> 
>> Another way is using a pre-programmed PIC chip available by Microchip
>> with USB to-Serial software plus a RS485 tranceiver chip.
>>
> +1 if OP wants to use standard hw...

Discussion elsewhere suggests that the RPi has an internal 16550 port, 
and controlling the 485 signals using e.g. CTS might be viable.

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. 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.

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

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