emulator lock up and tty bug

[curt mayer]

I'm having fun with my new imsai, but there have been a number of times where the front panel becomes completely unresponsive.

the UI still seems to be live, since refreshing the SYS: window causes the uptime report to increment.

a quick way to reproduce this is to copy over the cpm3-8080-2.dsk from z80 pack, and executing cpmldr.com.

i'd not expect this to work, but i'd also not expect it to hang like this.

not related, but sometimes in the TTY emulator window in the UI, DIR results in doubled characters.

--curt

[Udo Munk]

On Saturday, March 28, 2020 at 2:16:00 AM UTC+1, curt mayer wrote:

I'm having fun with my new imsai, but there have been a number of times where the front panel becomes completely unresponsive.

the UI still seems to be live, since refreshing the SYS: window causes the uptime report to increment.

a quick way to reproduce this is to copy over the cpm3-8080-2.dsk from z80 pack, and executing cpmldr.com.

i'd not expect this to work, but i'd also not expect it to hang like this.

In this case the CPU will run into a HLT instruction and you should see the HLT LED on. You should be able to

get out of halted state with reset or a power cycle, but the instruction is buggy it seems. 

not related, but sometimes in the TTY emulator window in the UI, DIR results in doubled characters.

I have not seen this so far, is there any way to reproduce it? 

[Ted Kekatos]

For the Double Characters issue, check out this post 

https://groups.google.com/forum/?nomobile=true#!topic/imsai8080esp/jwpD237jk10

Hoping this helps you.      

Congrats on building your new IMSAI 8080.   We love to see pictures of your build.    :-)  

[curt mayer]

re: lockup.  yes, the HLTA light is lit.   my real imsai does in fact reset out of a HLTA state.

thanks for the pointer to the fix for the web TTY interface.   

[Steve Tockey]

Curt,

Ted's referenced fix did clear up the double characters issue for me. Regarding the unresponsive front panel, I don't think you're the only one. I also see an occasional freeze. It just locks up and the only way out is to hit Reset on the esp32. I have not noticed any pattern to the freezes, they seem to occur fairly randomly for me. I have not kept detailed notes but I would estimate on the order of one freeze per hour of use.

Is anyone else seeing their IMSAI freeze requiring a Reset on the esp32?

[TheHighNibble]

Curt,

if you can put some notes on the HLTA issue including a simple and reproducible test case that I can use to make it happen I will endeavour to fix the bug.

Sorry about the (known) double character issue, when it was found I thought I'd be putting out a new firmware release any day and it would get permanently fixed but that hasn't happened. I realise that the work around isn't obvious unless you've been closely following the forum.

Steve T - I am surprised that you are having such regular lockups. I can and do leave my IMSAI8080esp running for days at a time without problems. So if you can identify a pattern and  maybe set the log level to INFO and keep the USB connected to a PC and capture the logs to see if they shed light on the problem, then you could send me the logs.

[Steve Tockey]

I will take more careful notes next time and forward them as soon as I can.

[curt mayer]

The lockups I have seen are 100% related to the HLTA light being lit.

Repro: deposit 0x76 at any writable address.  Examine. Step. Hang.

--curt

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[Steve Tockey]

Dave,

Some slightly more careful notes:

I ran last Sunday for 2.75 hours and had 3 separate lock ups. But that was before I reconfigured things. I had been powering the ESP32 directly from a 2.5A wall wart so I couldn't catch the log messages.

The new configuration has the ESP32 logging level set to INFO. And it is now powered from a USB3.0 port on a Raspberry Pi 4 with putty configured to catch the log messages. I haven't had a single freeze since then with about an equivalent amount of usage time.

I wonder if the wall wart power supply is flakey, maybe it is causing the problems. More experimentation will be required to verify, but the IMSAI 8080 is definitely more stable now.

[TheHighNibble]

Steve,

we have seen issues with marginal power supplies. Mostly causing random faults that go away when I decent supply or cable is substituted.

[Chuck McManis]

Here was an interesting video of a guy using level shifters to power an LED user interface. It has a REALLY good description of both how the level shifters work and how you can get caught out by a marginal supply especially if you are trying to run things quickly through the shifter.

https://www.youtube.com/watch?v=XWPPPL-tfEI

Recommended!

--Chuck

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[Steve Tockey]

Chuck,

Thanks for sharing that. yes, it was interesting. I agree that those el-cheapo cell phone chargers are crap. False advertising in terms of product specs. On the other hand, I was using what I thought should have been a reasonably high quality power supply. I guess one can never be sure.

[TheHighNibble]

Regarding the lock-up on Halt (HLTA is lit):

I have identified the problem and am testing the fix. Certainly now works the same as in the upstream Z80PACK.

I will publish a new firmware revision in the next 48 hours.

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