Rich Mellor wrote, on 20/Apr/11 12:45 | Apr20:
On 20/04/2011 12:25, Adrian Ives wrote:
Thanks to Rich Mellor, who managed to source a Hermes chip, I can now
confirm that the Ser-USB will work on a standard QL fitted with Hermes at
speeds up to 19200 baud. It is still necessary to load the
asynchronous I/O
module (the Queue Manager), though. This takes up an extra 5K of RAM.
It had been my intention to withdraw support for the Ser-USB on
standard QL
hardware, but after receiving some feedback on that, I went back to
the code
to see if there was anything that could be done to at least create
something
that was stable enough to be used with some limitations in that
environment.
I believe that effort has been successful; this was the result:
- The problem of executable files being corrupted when read back using
asynchronous I/O has been fixed, after eventually having been traced
to some
erroneous pointer arithmetic.
- Out of order Trap #3 requests no longer cause the driver to abort.
Instead, the driver attempts to gracefully bring the "abandoned"
request to
completion, deferring any other pending requests until the process is
completed.
Both of these issues only affected asynchronous I/O, but when combined
they
made the driver unreliable on systems that required that functionality.
Many thanks to everyone who pointed me at the SimSer serial driver as a
possible solution. I did spend some time looking at this, but as it only
enhances the functionality of the unidirectional channels (SRX and STX) I
was not able to immediately make use of its capabilities without quite
a bit
of rewriting. It does have some very useful features, though, and I will
look at providing support for them in a later version of the driver.
So . Ser-USB will be supported on base QL hardware, after all. However,
without Hermes or (better still) superHermes you will be limited to 4800
baud.
There will be an announcement at the beginning of May on the
availability of
the hardware and its pricing, before which I will be in touch with anyone
who has already enquired about purchasing a Ser-USB.
That is much welcome news - especially now even the low cost Hermes chip
means a 4 x speed improvement for standard QL users !
NOT four times. The 8749/8049 is input limited to something like 14kbps
throughput, so slightly less than three times. It is a nominal 19200
only. superHermes does give a full 19200 ser1/2 input, but of course
ser3 will then be used.
Adrian - sorry I didn't send you a Hermes chip but I have had no time
for QL work for quite a while (except a failed attempt to manufacture
for Rich).
Tony
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