Ralph S Bacon

MicroControllers, Electronics and IOT

If at first you don’t succeed…

I can’t believe it’s been a month since my last entry here. In that time I’ve enjoyed my vacation, but like all things came to an end and I’ve been back for two weeks already.

Two weeks, two videos. The last one was particularly interesting, where the Raspberry Pi and an Arduino ATTiny85 joined forces. Just goes to show how small the microcomputing world can be!

RaspberryPi

RIP my original Raspberry Pi Model 3B+

I moaned a bit that my ATTiny85 module (without any USB to Serial chip) was no longer recognised by my PC and I just got “The last USB device you plugged in went foobar“, (I paraphrase the Windows’ actual message, obviously).

Almost immediately you guys reminded me of the old adage “Don’t assume, or you will make an ass out of you and me”. Well, I’m the ass, as I totally assumed the Tiny85 would come complete with a bootloader that would allow me to use it. It never occurred to me that the (clone) Digispark board would be either bootloader-absent or contain a bootloader that wasn’t suitable. Doh! (Slaps forehead). Every Arduino-based module I’ve ever bought has both bootloader and the blink program installed (so far) except for some naked ATmega328P chips. Hence my assumption. Doh!

Anyway, I’ve downloaded the Micronucleus bootloader and used the avrdude utility (normally called in the background by the Arduino IDE compiler routine) with various parameters to upload a sketch to it and this is what I got:

Running Digispark Uploader…
Plug in device now… (will timeout in 60 seconds)
> Please plug in the device …
> Press CTRL+C to terminate the program.
> Device is found!
connecting: 16% complete
connecting: 22% complete
connecting: 28% complete
connecting: 33% complete
> Device has firmware version 2.3
> Device signature: 0x1e930b
> Available space for user applications: 6522 bytes
> Suggested sleep time between sending pages: 7ms
> Whole page count: 102 page size: 64
> Erase function sleep duration: 714ms
parsing: 50% complete
> Erasing the memory …
erasing: 55% complete
erasing: 60% complete
erasing: 65% complete
> Starting to upload …
writing: 70% complete
writing: 75% complete
writing: 80% complete
> Starting the user app …
running: 100% complete
>> Micronucleus done. Thank you!

In other words: success! Windows still complained about an unknown USB device but at least I can now program directly using the USB socket on the board. No Arduino required (other than to flash the bootloader, initially).

Perhaps I should do a new video on how to do this, given that something has changed in the time I did my last video on the ATTiny85 Digistump drivers, almost two years ago. I was probably running Windows 7 at the time, come to think of it. Hmm.

ArduinoAsISP

Programming the ATTiny85 using an Arduino UNO

It was, however, just as easy to program the ATTiny85 using an Arduino as ISP. Perhaps I should show both methods. Hmm.

And thank you to those who sent commiserations at the loss of my Raspberry Pi, once again all my own fault, as I tried to measure the 3.3-volt pin across from the 5v pin. When the two get shorted together only bad things happen. Scouring the internet to see whether my board could be salvaged (spoiler: no) it appears many people have done similarly silly things, including shorting the 3.3v or 5v pin to ground.

Electronic components can be fragile. I’ve killed a few MOSFETs just by handling them. But to kill an entire microcomputer board requires a special kind of carelessness. I’m now £35 the poorer (in fact, £70 as I bought two boards in case I ever did anything like this again and to have one for experimentation and one for my workshop automation project). So that’s all my ad revenue money from Google / YouTube from the last two months gone in a moment’s carelessness. Ouch. Double Ouch. Lesson learned, I hope.

See you in the next video, thanks for reading!

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4 replies

  1. Hi Ralph, Having watched Video 124 (RPi UPS) a number of times I didn’t spot the dreaded ‘lightning strike’ symbol. I now have two of the identical hats from the same supplier and the symbol appears irregularly, and the Pi red LED goes on and off to coincide (more or less). I have tried the obvious – a known good LiPo battery (in case of ‘disparity’ between claimed capacity and actual ! ), and also a 3A wallwart. No joy.
    Measuring the 5V rail (carefully ! ) it irregularly varies between 5.1 V and 4.85V. My DVM may not ‘catch’ excursions outside that range. Both of these are within Pi working tolerance to the best of my knowledge. Before I start decoupling the 5V rail with large electrolytics, did you encounter the above? Perhaps your unfortunate exploration of the 5V supply was in this context ?
    It confirms my view that monitoring the 5V rail to initiate an orderly shut-down is not the best way forward.
    Regards

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    • Just to clarify:
      The above comments were written when the UPS HAT suggested that the battery was fully charged – 4 Blue LEDs. – and the measured 5V rail was varying. Some hours later the indicated (on my DVM) rail is 5.13V and seems stable (though there may be undetected spikes ?) . However, the red Pi LED still occasionally extinguishes and the lightning strike appears – so the setup is still not performing correctly as it should. Time for some decoupling I think !

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  2. I am glad you were able to recover the ability to program the Digispark modules. Hopefully there is a way forward to fix the “unknown USB device” so that you can take full advantage of their HID capability too.

    Regarding your RasPi, I wonder if any of the on board protection has worked during your short circuit? Maybe there is just a fuse or regulator blown which could be replaced? Could make an interesting repair video if you still have the board.

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  3. Whilst components are generally ‘cheap’ the cost of simple mistakes can mount up. I have ruined two buck step-down modules this weekend. Hey ho, Amazon calls.

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