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

Lukasz Sokol el.es.cr at gmail.com
Thu Jul 4 17:46:31 CEST 2013

On 04/07/2013 16:24, Mark Morgan Lloyd wrote:
> 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.

Yeah I seem to remember http://www.hobbytronics.co.uk/raspberry-pi-gpio-pinout
I guess for 485 direction setting, one of GPIO will need to be used;
Sigh. Why do people keep reinventing ethernet starting from half duplex without
galv. separation ? :)

> 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.
Well that's a question of OP's project goals agenda...


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