[E3-hacking] Serial port oddity

[David Given]

I realise that the E3 is almost entirely irrelevant these days, but just
in case anyone wants to get one working...

I recently pulled mine out of storage and tried to put Debian on it. (I
want to use it as a modem.) Unfortunately PBL wouldn't handshake.
Investigation showed that at baud rates of 57600 and above, the E3's
serial port seemed to be unable to receive data reliably, getting
frequent single-bit errors. Transmission seems fine.

I eventually managed to get everything working by dropping the baud rate
to 38400 (uploading the kernel and initrd takes an *age* at that speed),
and everything works now.

This might be age-related; my E3 is now years old. A flaky capacitor
causing the pulses to get smeared so that the UART isn't registering
them properly? This seems particularly likely given that I don't have a
level shifter, so I'm driving the UART at out-of-spec voltages.
Alternatively it could be clock drift, but given that the UART is on the
processor this seems unlikely.

So if anyone has an E3 which won't handshake any more, try lowering the
baud rate and seeing if that helps. (pblq has an option for this.)

...

Incidentally, I don't suppose any of the uboot patches got accepted by
upstream, did they? Editing the environment with a hex editor is
slightly harrowing and it'd be so nice to have a version which could
store them in NAND...
--
???? ?????????????? ????? http://www.cowlark.com ?????
? "I have always wished for my computer to be as easy to use as my
? telephone; my wish has come true because I can no longer figure out
? how to use my telephone." --- Bjarne Stroustrup

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[Mr.G]

My development stopped at a controller for Christmas lights. I still have
two virgin units unopened in their boxes.

Post by David Given
I realise that the E3 is almost entirely irrelevant these days, but just
in case anyone wants to get one working...
I recently pulled mine out of storage and tried to put Debian on it. (I
want to use it as a modem.) Unfortunately PBL wouldn't handshake.
Investigation showed that at baud rates of 57600 and above, the E3's
serial port seemed to be unable to receive data reliably, getting
frequent single-bit errors. Transmission seems fine.
I eventually managed to get everything working by dropping the baud rate
to 38400 (uploading the kernel and initrd takes an *age* at that speed),
and everything works now.
This might be age-related; my E3 is now years old. A flaky capacitor
causing the pulses to get smeared so that the UART isn't registering
them properly? This seems particularly likely given that I don't have a
level shifter, so I'm driving the UART at out-of-spec voltages.
Alternatively it could be clock drift, but given that the UART is on the
processor this seems unlikely.
So if anyone has an E3 which won't handshake any more, try lowering the
baud rate and seeing if that helps. (pblq has an option for this.)
...
Incidentally, I don't suppose any of the uboot patches got accepted by
upstream, did they? Editing the environment with a hex editor is
slightly harrowing and it'd be so nice to have a version which could
store them in NAND...
--
???? ?????????????? ????? http://www.cowlark.com ?????
? "I have always wished for my computer to be as easy to use as my
? telephone; my wish has come true because I can no longer figure out
? how to use my telephone." --- Bjarne Stroustrup
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[Janusz Krzysztofik]

Post by David Given
I realise that the E3 is almost entirely irrelevant these days, but just
in case anyone wants to get one working...
I recently pulled mine out of storage and tried to put Debian on it.

A Debian on Amstrad Delta howto posted to the list could be a nice thing
for those who may want to give it a try. Personally, I've been using
Debian for years, but never tried to install it on any of my E3's, which
are running Angstrom, so I'm not the right person to write such howto.

BTW, I found writing an Angstrom howto a nightmare due to its instability when it came to upgrading the set of packages I had managed
to build and install two years ago. I must had been lucky while doing
that, as my consecutive upgrade attempts all failed. I'm still running
that 2 years old userspace, as well as booting that 5 years old installation ram disk on recent kernels without problems.

Post by David Given
(I
want to use it as a modem.) Unfortunately PBL wouldn't handshake.
Investigation showed that at baud rates of 57600 and above, the E3's
serial port seemed to be unable to receive data reliably, getting
frequent single-bit errors. Transmission seems fine.
I eventually managed to get everything working by dropping the baud rate
to 38400 (uploading the kernel and initrd takes an *age* at that speed),
and everything works now.

From my experience, it depends much on the serial port/adapter you use.
I had been fighting with several USB models for months before I
discovered that best results I can get with the regular serial port
found on one of my PC motherboards.

Post by David Given
This might be age-related; my E3 is now years old. A flaky capacitor
causing the pulses to get smeared so that the UART isn't registering
them properly? This seems particularly likely given that I don't have a
level shifter, so I'm driving the UART at out-of-spec voltages.
Alternatively it could be clock drift, but given that the UART is on the
processor this seems unlikely.
So if anyone has an E3 which won't handshake any more, try lowering the
baud rate and seeing if that helps. (pblq has an option for this.)

I've never used pblq, only pbltool found in
http://the.earth.li/pub/e3/E3_release_v2.tar.gz. Perhaps that makes a
difference.

Post by David Given
...
Incidentally, I don't suppose any of the uboot patches got accepted by
upstream, did they? Editing the environment with a hex editor is
slightly harrowing and it'd be so nice to have a version which could
store them in NAND...

I tried once to refresh those patches on top of current PBL version, but
failed due to lack of spare time. Perhaps some time I'll get back to
that once again if nobody else does it.

Thanks,
Janusz