[En-Nut-Discussion] Ethernut 3.1 RS232 hardware handshake

[Paul Govers]

Hey Harald,

Thanx for your fast reply!
i have tried to set the RTS and DTR bit and also all cable combination on 
page
http://www.ethernut.de/en/documents/rs232primer.html but it nothing worked 
:-(

i have also measured the DC voltage level on every pin on the RS 232 
connector(devices not connected), and this was the result

All RS232 pins on the ethernut3.1d 0 Volt
All RS232 pins on the Remeha Heating system 0 Volt

Computer rs232 pin1: 0volt
Computer rs232 pin2: 0volt
Computer rs232 pin3: -11volt
Computer rs232 pin4: 11volt
Computer rs232 pin5: 0volt
Computer rs232 pin6: 0volt
Computer rs232 pin7: 11volt
Computer rs232 pin8: 0volt
Computer rs232 pin9: 0volt

it looks like if the computer RS232 port is running in a different mode as 
the ethernut

The ethernut and Remaha heating system has all pins on 0volt, so shortened 
handshake signals pins does not have any affect.
iam not a RS232 expert, but maybe it is possible to set the ethernut RS232 
port in the same "mode" as the computer? (because computer RS232 connected 
to heating system is working just fine)

Greetings

----- Original Message ----- 
From: "Harald Kipp" <harald.kipp at egnite.de>
To: "Ethernut User Chat (English)" <en-nut-discussion at egnite.de>
Sent: Monday, November 30, 2009 2:16 PM
Subject: Re: [En-Nut-Discussion] Ethernut 3.1 RS232 hardware handshake


> Hi Paul,
>
> Paul Govers wrote:
>> but now i want to connect my Remeha Heating system to the ethernut with a 
>> serial cable, both devices has a comport. When i connect my laptop to the 
>> remeha heating system i get data from it(rs232|9600baud|no flowcontrol), 
>> i can see the data with a serial program called "Advanced Serial Port 
>> Terminal". But when i connect my remeha heating system to the ethernut i 
>> receive nothing :-(  i connected a scoop to pin 2 and pin 3 but still no 
>> data
>
> Hardware handshake support for the Ethernut 3 CPLD had been added
> recently to Nut/OS 4.9.
>
> http://ethernut.svn.sourceforge.net/viewvc/ethernut/trunk/nut/arch/arm/dev/usartat91.c?r1=2602&r2=2670
>
> It is not yet available in 4.8. The changes are somewhat extensive and I
> didn't want to risk spoiling the stable version.
>
> In your case, however, it looks to me that you won't need real
> handshaking. Just enabling the handshake lines should do the job.
>
> Have a look to
>
> http://www.ethernut.de/en/hardware/enut3/cpld.html
>
> Setting RSRTS and RSDTR bits in register NPL_RSCR will activate the
> handshake outputs. Simply add the following to your main():
>
> #include <dev/npl.h>
> ...
> sbi(NPL_RSCR, NPL_RSRTS_BIT);
> sbi(NPL_RSCR, NPL_RSDTR_BIT);
>
> As an alternative you can also use a different wiring of the RS-232
> cable as explained in
>
> http://www.ethernut.de/en/documents/rs232primer.html
> (shortened handshake signals)
>
> Please let me know if it helped.
>
> Harald
>
>
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