Subject:
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Re: patch for lnpd ( Collision problem in far-mode )
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Sun, 13 Feb 2000 02:03:49 GMT
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Viewed:
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6609 times
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No matter what I do (opening the window, turning on more lights etc) I can't
get the tower to stop seeing collissions. I must admit that IR reflects so
well in my house that the TV remote works form other rooms.
So I tried loading your patch Martin. Sorry to be a pain, I assume this is how
I apply the patch you wrote?
abacus:~/lego/lnpd+liblnp/lnpd$ patch transceiver.c patch-trans
patching file `transceiver.c'
patch: **** malformed patch at line 4: static unsigned char* tx_next;
I need to be told I am an idoit every now and then :)
Michael.
In lugnet.robotics.rcx.legos, Martin Cornelius writes:
> Toni Martinez-Colom wrote:
> >
> > I have observed the same behavior... only by night. I think it must be the
> > tower receiving echoes of its own packets.
>
>
> i had never seen this interesting effect, because i always had my tower
> in near mode, where it only happens if you put the tower straight in
> front of a wall. I suspect it's a little more complex to explain what
> happens here, because the tower always receives it's own packets -- this
> actually is the principle of collision detection. We just test if every
> byte we sent out comes back immediately, if not, or the uart tells us a
> framing error occured, we regard this as a collision.
>
> I guess there is some analog circuitry inside the tower that screws up
> sometimes. If you modifiy lnptest to have the packets sent contain all
> the same value in the data section, there are much less errors.
>
> However, i found some kind of solution, that seems to make things much
> better. I just removed the frame-error checking code from lnpd.
> Actually, this code is not necessary, we have a checksum at the end of
> each frame that should detect garbled data anyways. Obviously the uart
> often detects frame errors although the content of the byte was received
> correctly.
> Perhaps we could also remove frame error detection from legOS with
> positive results, i`ll check that.
> Anyways, here is the patch for lnpd: You can still get the
> frame-checking by adding -DCHECK_FRAMING to the CFLAGS, but by default
> it will not be there, making lnpd even a little smaller.
>
> Please, tell me if that helps, Martin
>
> ------------- snip here -------------------
> --- transceiver.c.old Sat Feb 12 23:12:20 2000
> +++ transceiver.c Sat Feb 12 23:08:45 2000
> @@ -32,9 +32,11 @@
> static unsigned char* tx_next;
> static unsigned char* tx_verify;
> static unsigned char* tx_end;
> -static struct serial_icounter_struct tty_error_info;
> static struct timeval inter_byte_time, keep_alive_time,
> tx_allowed_time;
> static const unsigned char keepalive_byte = KEEP_ALIVE_BYTE;
> +#ifdef CHECK_FRAMING
> +static struct serial_icounter_struct tty_error_info;
> +#endif
>
> // convert a time in milliseconds to struct timeval
> static void msecs2timeval(int msecs, struct timeval *tval)
> @@ -58,7 +60,7 @@
> int result = select(0,NULL,NULL,NULL,&wtime);
> if ( result < 0 && errno != EINTR ) error_exit("select()");
> if (gettimeofday(&now,NULL)) error_exit("gettimeofday");
> - if (timercmp(&now,&end,>)) break;
> + if (!timercmp(&now,&end,<)) break;
> timersub(&end,&now,&wtime);
> } while (1);
> }
> @@ -94,7 +96,9 @@
> static void rx_flush(void)
> {
> if ( tcflush(rcxfd,TCIFLUSH)) error_exit("tcflush");
> +#ifdef CHECK_FRAMING
> if ( ioctl(rcxfd,TIOCGICOUNT,&tty_error_info)) error_exit(ioctl);
> +#endif
> }
>
> // discard all characters in the output queue of tty
> @@ -156,10 +160,14 @@
>
> static int rcx_read(void)
> {
> - int badframe, bytes_read, total_read = 0;
> + int bytes_read, total_read = 0;
> unsigned char rcv_buffer[RCV_BUFFER_SIZE];
> unsigned char *rcvd;
> +
> +#ifdef CHECK_FRAMING
> + int badframe;
> struct serial_icounter_struct new_error_info;
> +#endif
>
> while (1)
> {
> @@ -170,6 +178,7 @@
> if ( bytes_read < 0 ) error_exit("read");
> // log(LNPD_LOG_DEBUG,"read %d from tty",bytes_read);
>
> +#ifdef CHECK_FRAMING
> // check for frame errors
> if ( ioctl(rcxfd,TIOCGICOUNT,&new_error_info))
> error_exit("ioctl");
> badframe =
> @@ -187,6 +196,7 @@
> log(LNPD_LOG_LOGICAL,"Frame Error");
> break;
> }
> +#endif
>
> for (rcvd = rcv_buffer; rcvd < rcv_buffer + bytes_read ; • ++rcvd)
> {
> @@ -269,7 +279,9 @@
> // wait for IR to settle
> msleep(100);
> rx_flush();
> +#ifdef CHECK_FRAMING
> if ( ioctl(rcxfd,TIOCGICOUNT,&tty_error_info)) error_exit("ioctl");
> +#endif
>
> // check if we can read back what we sent
> write(rcxfd,&keepalive_byte,1);
> ------------- snip here -------------------
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