Try some other commands to the mcu, if it doesn’t answer then go over the pin outs again. Make sure its wired exactly like hoop’s guide.
I had mine wired like the wiki guide and worked fine for years using the attiny13 but when I tried the attiny85 it gave me the message your seeing and would not talk to the mcu.
Took it all apart and wired it up like hoop, no more problems. Just a suggestion, it still could have some other problem…
Do you have any suggestions for commands to test?
Wiring is all good, checked and tested again on a D1 (also uses attiny85 - in fact I think the whole driver is the same but with slightly different firmware config settings).
I think it is this one. Its been awhile since I have programmed anything.
avrdude -p t85 -c usbasp -n
Ah yes, good memory, that’s the command I’m using to test the connection before flashing but it falls over with “target doesn’t answer” warning.
If it works on the D1 then there is some other problem or a bad connection.
Hmm ok, I might try sourcing and flashing a new chip to reflow onto the D4. Just to double check the chip, is the correct chip ATTINY85-20SH and not the lower voltage one ATTINY85V-10SH? Also is there any reason to use the U version opposed to H? According to the datasheet the U indicates matte tin and H indicates NiPdAu lead finish.
I buy the 20SU's and think in general, these are the ones most used. I get them from either MtnE or arrow.com. Last order was from Arrow: https://www.arrow.com/en/products/attiny85-20su/microchip-technology, great price for 10+ (I ordered 15 because I was down to 1 remaining) and free shipping (US), but if I have a MtnE order going in anyway, I'll add some 85's.
Don't think it's all that important which version, but not sure. Could be the SU's are more readily available or cheaper, dunno.
I also added my favorite FET in the arrow order: Infineon BSC009NE2LS5ATMA1, https://www.arrow.com/en/products/bsc009ne2ls5atma1/infineon-technologies-ag, again at qty 10 (I ordered 12) at $1.35 free shipping, better than the SIR800DP. The better Vishay FET's are the SIR404DP and SIRA20DP, but the A20 can be finicky.
Thanks Tom! I’m in the UK and shipping is a bit steep from MtnE, they have lots of cool stuff though.
Wow, on Arrow the SH is double the price of the SU. Locally, the SH is the same price as the SU!
FWIW, I also have a D4 with a stubborn MCU. So far i have flashed 2 x D4, 2x BLF A6 and a Q8 with the 8-pin clip (plus 2 x D4S with PINS).
But for some reason the newest of my three D4’s denies being flashed. I have made multiple tries, flashing an other light, confirming it works, then flashing the new D4. Same result every time 
So one of my three D4’s are running stock RampingOS2 
With my hot air station, it's soo easy to remove the MCU, and about equally as easy to reflow one back on. Does make you wonder if they locked a batch of them - Hank might not even know a subcontractor did it, they just might be used to doing it. I recall I ordered a batch of Attiny13A's one off of eBay - none of them could be programmed, and I did eventually get my money back but this guy totally denied they were used, pre-programmed (and locked) parts. Probably he just did not know.
The 20SU’s is what I have always used replacing the mcu’s on all the BLF X6 and A6 drivers I have modified. Never had a problem.
The hot air station makes replacing these little 8 legged parts a breeze. Reflowed a 20 pin attiny841 QFN last night, a hot air station makes it like cheating, it’s so easy.
Using reflow flux is almost a must have.
I use loose MCU to see if it takes. Then try it on a spare driver. I ordered one of the 826D+ stations, was supposed to be here today. Didn’t show. I have reflow a few with my Roneson hobby torch but its scary.
The 826 or the 862?
I would not invest too much money in these combo units. The $40 858 should be fine for hot air.
If you plan to use the iron from the 826, get some genuine Hakko T18 tips to at least give you some decent performance. I’d also recommend a $15 FG-100 to verify your iron temperatures.
Believe it or not, but some people will use a cheap hot air gun from the hardware store for reflowing. You don’t get the nozzles, but it does work.
Had to look its the 826D+
Edit, I got the 3 year protection plan from amazon.
If it last 3 years I will get another.
Edit again 826D+
Okay, that’s the cheap one. The 826 is like $170! :disappointed:
Did you pay a lot?
My last one was the YiHUA-936B ($17). I think the iron finally gave out. I was going to order a replacement. But wanted to try something different.
I really like the 936B. So I may still order a replacement iron. There cheap.
Pretty sure mine is a 858D on Amazon for about $42. I will never give up or replace my Hakko station - I became an instant soldering expert as soon as I got it.
With the hot air, if you want to do LED reflows, simply crank up the heat, heat from underneath - with the good copper MCPCB's, might take 450C but it works.
Tom E. I didn’t see a 858D on Amazon. This is the one I got comming.
Irons like the 936 with cheap tips are adequate for light duty stuff (like small smd components), but not for solder blobbing batteries or anything that requires some real grunt. Using genuine Hakko T18 tips does improve their performance, though. All in my opinion.
I’ve switched over to a much better unit that was $60. I’ll be writing up a review on it soon.
The 888 ($100) or 951 ($230)?
I considered the 951 due to the cartridge style tips, but the user interface would drive me nuts. Plus it’s much too expensive for what you get in my opinion. I considered getting an entry-level JBC unit for about $500, but I think I found something just as good for a fraction of the price.