QL-SD card project

[Peter]

A question. Could some of the problems be due to a poor ground layout / tracks? Are you seeing a form of "ground bounce" where the voltage drop through the ground is helping to cause the voltage on the signal lines to be out of spec?
Mark

Yes the QL mainboard ground layout is poor and involved in the problems. No plane and very long tracks. For the 68008 it is already not nice, but for the SGC with it's faster edge timings it is a real pain. Signal impedances are undefined and you have all combinations of crosstalk, reflections and ground bouncing. (My scope GND point was the ROM socket, because thats what the QL-SD PLD refers to.)

It would be interesting to compare with the Aurora mainboard, which has a good layout.

[Nasta]

Critical signals (that are used as qualifiers for other signals, i.e. to latch them) could be buffered by a HCMOS buffer which has 1/3 - 2/3 Vcc tresholds for logic zero and 1. Something like a HC244 also has a narrow schmitt characteristic which could help.

[Peter]

Or not break the form factor by adding components, but go back to a classic 5V PLD. Or move things out to the external ROM port, as signal quality seems somewhat better there.

The more basic question is, wether to continue tinkering or not. I tend to say, the device should become available as it is. Testing with normal QLs was intense and successful, so things can start rolling without the (S)GC.

Do you have any estimate how may Aurora users might still be active? Is the Aurora DIL socket pinout for QL ROM or EPROM? (QL-SD requires QL ROM pinout on the bottom, and has Minerva-style EPROM on top.)

[Nasta]

Aurora has jumpers to set the type of ROM/EPROM. If you piggyback the two original ROMs and set the right jumper combination, you get ROM socket compatibility (just keep in mind the Aurora has a 32-pin DIL socket for the ROM, align the pins correctly).

[Peter]

Thanks. Should have known you made a neat solution. Unfortunately I own no Aurora system - would be interesting to see if my SGC becomes stable with QL-SD then.

[Peter]

Hi all,

an update on this project:

I'm working on a test board and a special PLD logic which allows detailed checks of the main QL-SD unit (the "QLROMEXT" board). It semi-automatically tests all the relevant signals and displays the result by LEDs.

The test is performed independently, outside the QL. In case of a fault, the test board determines exactly which signal(s) are affected. It can be used during early production, while it is still relatively easy to correct soldering issues with the fine pitch SMD components used by QL-SD.

Sorry for the delay in releasing the QL-SD driver source code, which is caused by developing this equipment. At the upcoming German SInclair meeting, we will discuss and implement the details of the test process. I hope this tool will help to make QL-SD production more efficient.

Peter

[vanpeebles]

I'm really impressed with the QL-SD, I love mine It works great with ACT, speeds up the text compression and the final compile. I've barely touched a floppy disc since I fitted it. Just need to do my little write up for the QUANTA mag.

[Dave]

Those 0.5mm QFP pins are tricky to hand assemble. I imagine once you've put the DIP socket on, it makes it really hard to do rework on it.

[Peter]

Yes, therefore the test board can be used even before the DIP Socket is soldered. The object under test is then pressed into lines of conical pins. The oscillator is also tricky to solder - blinking LEDs show that it works.

[TabajaraLabs]

Is there a person who...

A) has spare time? (most important)
B) wants to build the QL-SD and learn the software/hardware issues?
C) owns a QL and is willing to use it for testing the QL-SD?
D) can solder TQFP and components with similarly small pads?
E) can deal with ROM binaries and has equipment to burn EPROMs?
F) has a Lattice programming adaptor or would buy one?
G) can source PCBs and electronic components, including difficulties like DIL sockets with long wires?
H) would find the QL-SD worthwhile as it is (internal, using ROM socket and microdrive slots)?
I) would accept instabilities with some SuperGoldCards, or find a solution?
J) can organize production and sales without help from my side?

I was glad Adrian was into all this - someone with his knowledge was ideal. I think financing the parts is not a problem, I can help with that if necessary. But I can not spend much time.

If I can be of any help, I have every letter but J. Unfortunately I don't have much time to organize production and sales. And remember, I live in Brazil. But being a embbedded hardware/software developer, and having a full lab oriented to building and debugging digital devices, I'm here to help.