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Forum Index : Microcontroller and PC projects : Picomite VGA Logic analyzer
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| Pluto Guru  Joined: 09/06/2017 Location: FinlandPosts: 358 |
Made an isolated input for the Logic Analyzer (LA_21) by using Si8660 LOW POWER SIX-CHANNEL DIGITAL ISOLATOR. Works fine at least for I2C, not yet tested with SPI. Isolates the measurement inputs from PicoMite and makes the inputs 5V tolerant. Just for testing. I have the input part suppled from USB 5V and the output supplied from Pico's 3.3V. If properly done, the input should be powered a from separate isolated supply (e.g. battery, 2.5-5.5V). Made it because I have some trouble with static electricity shutting down the Pico from time to time. Sometimes the program is erased, but more frequently it starts again (OPTION AUTORUN ON). However, the isolator did not solve the problem with static electricity. /Pluto |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6792 |
The PicoMite shutting down occasionally could be a sign of a bad or marginal power supply rather than static electricity. The on-board SMPS usually isolates the 3V3 pretty effectively from the 5V input and allows for quite a voltage drop. There shouldn't be much noise or any spikes on the USB supply from a PC. It could be that all you need are some external pull down (or pull up as appropriate) resistors to discharge the gate capacitance of the PicoMite inputs. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Pluto Guru Joined: 09/06/2017 Location: FinlandPosts: 358 |
In my case it is definitely static electricity. It only happens when I approach and touch the workbench. Can also feel the characteristic small pain in my fingers.  It is winter here in Finland and the humidity is low. Excellent opportunity for creating static electricity. Not enough to heat the house  , but only a finger or two. |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4235 |
Hi Pluto, Yesterday I experience the same. But I was using a picomite to control a 1000Vdc generator, and when touching the 1000V with a multimeter probe, the picomite restarted (disconnecting USB...mind you, this is linux, putty, shuts down in that case...Windows teraterm will reconnect without issues). In my case the pico was on a breadboard. I blaimed the breadboard, and the poor ground layout between the instuments on my desk, where USB creates a ground loop. My circuit was a test setup, and I got the results. But it was anoying... In your case the problem may be coupling through the 5V USB and common ground. You can test this by powering the isolator primary side from a separate phone charger... Volhout Edited 2023-02-16 20:01 by Volhout PicomiteVGA PETSCII ROBOTS |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
Try a 10k from RUN pin to 3V3 (and perhaps a 100n from RUN to GND). The weak internal pullup makes it a bit too sensitive. Fixed it for me. |
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| Pluto Guru Joined: 09/06/2017 Location: FinlandPosts: 358 |
Thanks for the idea. I will try it. /Pluto |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6792 |
I'd be tempted to work on an antistatic mat and wear a wrist band connected to it. Static discharges and microcontrollers don't mix well You may be ok at first, but repeated discharges can weaken insulating layers on the die and give problems later. Normal precautions when working with CMOS. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4235 |
Hi phil99, This is a really good fix. I just added to 100n capacitor, and it made the pico much more robust against ESD discharges on my test table. I will rework all my picomite platforms to add this capacitor. The 10k may also help, but the capacitor was the dominant fix. Thanks !!! Volhout PicomiteVGA PETSCII ROBOTS |
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| Pluto Guru Joined: 09/06/2017 Location: FinlandPosts: 358 |
Thanks phil99. I connected only the 100n and did not see any problems since that.  /Pluto |
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| Pluto Guru Joined: 09/06/2017 Location: FinlandPosts: 358 |
Logic Analyzer LA_21: I had some problems with the newer firmwares (e.g.PicoMiteVGA MMBasic Version 5.07.07b22). The graph colors were OK only in the upper-left corner of the screen. The solution was simple: Adding the command "TILE LARGE" to the beginning of the program solvs the problem. Just in case somebody else run into the same problem. /Pluto |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4235 |
@pluto I did the same. Did not publish yet, since Peter is still working on 50707bxx. Things may still change. Volhout PicomiteVGA PETSCII ROBOTS |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4235 |
There is an update for the logic analyzer program. There are no features added, but changes to make it compatible with the latest MMBasic version. This version V50707b24 is adapted for color editor in mode 1. To support this is has a different tile size. The tiles are used to provide color in mode 1. With this new version MMBasic the colors on screen where mis aligned. This version fixes that. It has changes in screen setup, and in the time measurement function that highlights the measured section. LA21_b24.zip Put both files in 1 folder. Then run the LA_21_b24.bas. Regards, Volhout PicomiteVGA PETSCII ROBOTS |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4235 |
Please find attached user manual for the Picomite VGA logic analyzer. Feel free to comment. The document is in in .RTF format. I hope it is readable since I can't write in PDF at the moment. LA_userman.zip Volhout PicomiteVGA PETSCII ROBOTS |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6792 |
I write RTF files using Jarte Plus now. It's a nice editor, free and can print to PDF files. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Amnesie Guru Joined: 30/06/2020 Location: GermanyPosts: 396 |
Thank you for the manual, this makes things a lot easier! Greetings Daniel |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4235 |
You are welcome. I needed to write down instructions, and Tom asked for a manual, so here is it. Volhout.. PicomiteVGA PETSCII ROBOTS |
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thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4040 |
Neat, thank you @Volhout, I'll have to find time to have a play ... I wonder what I will analyse ... the signals from NES controllers perhaps  .Best wishes, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Pluto Guru Joined: 09/06/2017 Location: FinlandPosts: 358 |
You will probably have the play when you have your next communication problem... ...with sensors. I2C is in place and operational and SPI is also possible to encode (see much earlier posts), what would be the next preference? |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4235 |
Spi basis has been shown. Disadvantage of spi is that you need so much knowledge to set it up correctly for decoding that hardly anyone will succesfully use it. But maybe uart or onewire would be more usefull. But I tend more at the moment to finalising my chess program, so if you, pluto, want to pick up where I stopped, you are welcome. Edited 2023-03-12 08:08 by Volhout PicomiteVGA PETSCII ROBOTS |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4235 |
All, The Picomite VGA 5.07.07 is close to release. All bugs have been fixed. One fix affected the logic analyzer graphics. This is fixed in below version LA_22. Version LA_22 is functionally identical to LA_21, only modified to work with Picomite 50707. The user manual is included in the ZIP. Unpack all in a folder on the picomite, and run "LA_22.bas". Happy analyzing... Volhout LA22.zip Edited 2023-04-13 21:19 by Volhout PicomiteVGA PETSCII ROBOTS |
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