[erlang-questions] Binaries

[Bob Cowdery]

The first does nothing and the second hangs. It's not gen-serial that's 
having a problem with it. It's sending it and giving ok but when decoded 
in the radio which obviously I can't look at it isn't a valid command. 
The encoding of <<16#14,16#50,16#00,16#00,16#01>> and <<20,80,0,0,1>> is 
somehow different.


On 6/19/2018 5:37 PM, Danil Zagoskin wrote:
> That's how erlang part communicates with C part.
> https://github.com/tomszilagyi/gen_serial/blob/master/src/gen_serial.erl#L622
> -define(PACKET_DATA, $d).
>
> send(#gen_serial{port = Port}, Data) ->
>   true = port_command(Port, [<<?PACKET_DATA:8>> | Data]),
>   ok.
>
> Maybe port_command does not expect an improper list — try one of these:
> * gen_serial:bsend(P,[<<20,80,0,0,1>>]) % Your binary wrapped in a list
> * gen_serial:bsend(P,[20,80,0,0,1]) % data as list instead of binary
>
> On Tue, Jun 19, 2018 at 7:22 PM Bob Cowdery <bob@REDACTED 
> <mailto:bob@REDACTED>> wrote:
>
>     Thanks for all the suggestions. Still a little confused. The
>     number is
>     an integer, actually a frequency in Hz plus a command byte at the end
>     which is being sent over a serial connection in hex format using
>     gen_serial.
>
>     This command works: gen_serial:bsend(P,
>     <<16#14,16#50,16#00,16#00,16#01>>). where P is the open Port.
>
>     However, when I use any of the methods to create a hex version
>     they all
>     end up with <<20,80,0,0,1>> which to my mind is the decimal equiv
>     of above.
>
>     If I fire that I get:
>
>     5> gen_serial:bsend(P,<<20,80,0,0,1>>).
>     ** exception error: bad argument
>           in function  port_command/2
>              called as
>     port_command(#Port<0.470>,[<<"d">>|<<20,80,0,0,1>>])
>           in call from gen_serial:send/2 (gen_serial.erl, line 624)
>           in call from gen_serial:bsend/3 (gen_serial.erl, line 706)
>
>     What is <<"d">> doing in there?
>
>
>     On 6/19/2018 4:32 PM, Bob Cowdery wrote:
>     > If I have a number, say 1450000001 and I want to represent that
>     as a
>     > binary in the form
>     >
>     >  <<16#14,16#50,16#00,16#00,16#01>> what's the best way.
>     >
>     > I'm not sure what list_to_binary(integer_to_list(1450000001)) which
>     > prints as <<"1450000001">> produces but I guess its 10 bytes not 5.
>     >
>     > BobC
>     >
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>
> -- 
> Danil Zagoskin | z@REDACTED <mailto:z@REDACTED>

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