Microchip PIC Forum: Re: [piclist] Re: address decode on serial

You can't get a PC to generate it. PC UARTS aren't capable of it. You
need to get a RS485 module between the network and the PC to handle that
part of the protocol. With enough effort you might get the PC to do some
kind of parity bit fiddling to get it to work, but an interface dongle is
a bit simpler to manage I think.

DLC

> I read about the 9th bit address.....
>
> How do I get the pc to generate it? Im using QBASIC on the pc and
> not sure how to create a extra bit there.
>
> Randy
>
>
>
> -- In piclist@yahoogroups.com, "Dennis Clark" <dlc@...> wrote:
>>
>> You don't need to do that with the newer PICs. Read up on "9th bit
>> addressing" for the PIC. In this mode the 9th bit is set and the
> USART
>> recognizes this as an address. Your code then needs only to look
> for this
>> bit set to pay attention to a byte as an address.
>>
>> DLC
>>
>> > Hello all:
>> >
>> > I have a desire for a project to use a PC as a master, poll
> various
>> > pics on a rs485 network, using a very simple polling idea and
> have
>> > the pics respond with their status as well as take data from the
> pic
>> > if desired.
>> >
>> > Im working on this in small parts and my first thoughts on
> overall
>> > programming is this to get the pic to respond to its address:
>> >
>> > pic watches the data stream for a "sync byte" such as "89"
>> > if "89" appears then check the next byte for its address such
> as "02"
>> > if "02" is its address then respond with its status
>> >
>> > I tried this before without using the sync byte and the pic
>> > responded to any bit sequence that appeared and matched 4 bits.
> By
>> > using the sync byte, will this help with the false responses? my
>> > first attempt was using a addres of "2" and any bit opattern that
>> > matched "0010" falsed a response.
>> >
>> > Serial speed is not set, I tested at 9600.....
>> > PIC is 16F627/16F628
>> >
>> > Im a NOVICE to programming and trying to learn as I go here.
>> >
>> > All help appreciated!
>> >
>> > Randy
>> > kk4ej
>> >
>> >
>> >
>> >
>> > to unsubscribe, go to http://www.yahoogroups.com and follow the
>> > instructions
>> > Yahoo! Groups Links
>> >
>> >
>> >
>> >
>>
>>
>> --
>> Dennis Clark
>> TTT Enterprises
>>
>
>
>
>
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--
Dennis Clark
TTT Enterprises