QLAN-USB Adapter - working prototype...

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martyn_hill
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Re: QLAN-USB Adapter - working prototype...

Postby martyn_hill » Sat Dec 09, 2017 2:03 pm

Thanks for your post Whopper.

Steady progress is being made on the SMSQ/E NET driver re-write to communicate with the microcontroller in-place of the 'bit-banging' routine of the original physical TK2 NET driver.

Just to clarify my own intentions with this project - to share the microcontroller code (mostly completed and already working), the NET driver code for running on an emulator (will be tested on QPC primarily), parts list and instructions for programming the uC and how to wire it all up in hardware (the trivial bit!)

One of our hardware gurus on the forum may well be able to make this available as a ready-built commercial offering in the future, whilst I continue to develop and share publicly the software/design itself for the DIY'ers among us.

More to follow...


martyn_hill
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Re: QLAN-USB Adapter - working prototype...

Postby martyn_hill » Mon Jan 08, 2018 9:51 pm

A little update for those following this project...

On-going progress is being made with the interfacing between the microcontroller and SMSQ/E (to add-back the native NET and FSERVE/Nx_ device drivers) - should have more to report in the next few weeks.

Meanwhile, mostly out of curiosity, I picked-up a second-hand Spectrum and Interface-1 recently to compare the network timings - it has always been reported that QL to Spectrum networking only works 1-way.

I can confirm that QL to Spectrum works mostly OK, but packets from the Spectrum are unreliable. Timing traces show that the Speccy has slightly longer and sometimes variable bit-times (nominally, 11.4us rather than the QL's pretty consistent 11.2 us), along with significantly shorter 'lead' bits (3x rather than the QL's 4.5 - 5x bit times). This combination appears to hammer native QL reception.

I've since been able to adjust the microcontroller code to reliably speak to both QL and Spectrum nodes and added new debugging to facilitate further diagnosis.

Its still my intention to publish here all my findings and source code/hardware design in due course - just trying to avoid more distraction from writing the SMSQ/E driver interface...


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tofro
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Re: QLAN-USB Adapter - working prototype...

Postby tofro » Mon Jan 08, 2018 9:59 pm

Well, no wonder:

Both the Spectrum with I/F1 and the QL bit-bang the protocol at 87500 bps - Not an easy task for a poor Z80. It's probably at its limits.

Nice to hear you're making progress.

Tobias



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