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

[Lukasz Sokol]

On 04/07/2013 11:08, Dennis Poon wrote:
> thanks. I am not using the fpc email as it seems off topic.
> 
> May I know the exact brand and model number of the adapter you used? 
> I have an ATEN usb-to-serial cable (UC-232A) but I am not sure how to
> connect its serial pins to rs-485 's DIFFERENTIAL LINES and how to
> set that adapter into half-duplex translation mode.
> 
> Dennis
> 
[...]


(apparently it went into FPC list anyway)

For RS485 adaptation, use a MAX232 like chip (to convert +-12 to ttl) 
and then a RS485 transceiver chip; 

A MAX232 has 4 [IIRC] level changers, 2 in each direction; so you can
use one pair to convert tx/rx, and one of the remaining ones in 232-ttl direction,
to convert one RS232 signal to switch the RS485 trx into 'sending' mode;

Of course you need an additional +5V supply to the above too.

HTH,
-L.