USBTiny will not communicate with MCU

USB AVR Programmer and SPI interface. Adafruit's USBtinyISP.

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plc_gremlin
 
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USBTiny will not communicate with MCU

Post by plc_gremlin »

Received my USBTinyISP this week and am going insane trying to get it to talk to either an ATTiny85 (tried 2 different ones) or an Atmega328P.

I'm guessing that the USBTIny is talking to my Laptop properly as that I do get the message back from AVRDUDE "initialization failed, rc=-1' and the green led is lit.
I have been through a ton of the forum posts here looking for an answer as I assumed it was because I'm on Windows 8 = driver problems, etc..
When I run the AVRDUDE command "avrdude -c usbtiny -p t85", the red LED blinks and then I get the response posted above(init failed). I have also tried with various speeds using the -B switch.. -B 32, -B64, all the way to -B 250. By the way, 1 of my tiny85's is blank, the other I have programmed with the Arduino Mega as ISP previously. The 328P chip is new.
Here is what I've tried so far to rule things out.

I have tried getting it work on my newish Toshiba laptop (Windows 8) and I've tried it on an old desktop(Pentium4) with XP. Ive tried 3 different USB Cables on each.
I have pinned out all my connections with multimeter from the USBTIny all the way to the ATTiny85. Everything seems connected properly.
I have verified that USBTIny is supplying 5v and Gnd to my target chip.
I have connected my USB scope from ground to reset pin at my tiny85 and see that it pulls low when I run avrdude. It goes low for 51.6ms, back high for about 360us, then low again for 51.6ms.
The SCK, MOSI, MISO pins all have signals that make it down to the attiny85. I will attach waveforms below. The only thing that stands out is that the MOSI, MISO signals seem to be the same and they are a little skewed. See pics.
I'm sure I've tried other things that I cant remember.. possibly including sprinkling magic dust on it and wearing an aluminum foil helmet...

The question is,,.. .What else can I try to get this working? I would really love to be able to start programming these attiny85's.
USBTiny with ATTiny85.jpg
USBTiny with ATTiny85.jpg (466.29 KiB) Viewed 775 times
Usbtiny SCK Waveform.jpg
Usbtiny SCK Waveform.jpg (109.81 KiB) Viewed 775 times
Usbtiny MISO MOSI Waveform.jpg
Usbtiny MISO MOSI Waveform.jpg (101.51 KiB) Viewed 775 times

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plc_gremlin
 
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Re: USBTiny will not communicate with MCU

Post by plc_gremlin »

Wow..
After hours and hours of trying to get this to work and then finally taking the time to post this here for help, I was sitting trying to think of anything that I hadn't tried.

I thought of the resistors R4 and R7 that the guide tells us to just jumper if not using it for the SPOKEPOV...
As a last attempt for the night, I just clipped out my jumpers and soldered in the resistors and it WORKED!!!!!!!

You guys may want to think about modifying/clarifying the assembly guide to just go ahead and install the resistors and THEN jumper later if need be.

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plc_gremlin
 
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Re: USBTiny will not communicate with MCU

Post by plc_gremlin »

Figured I would go ahead and post another shot of the MISO / MOSI Waveform after installing the R4/R7 resistors.
Much cleaner now.
Usbtiny MISO MOSI Waveform w_Resistors.jpg
Usbtiny MISO MOSI Waveform w_Resistors.jpg (88.77 KiB) Viewed 760 times

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adafruit_support_mike
 
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Re: USBTiny will not communicate with MCU

Post by adafruit_support_mike »

Looks like we overlapped in posting. I was planning to ask about the 200mV/div scale in the first set of traces.. if that corresponds to the major divisions, the actual signals were only about 400mV. The second set of traces shows a much stronger signal.

If you would, the Learning System has a feedback button at the bottom of the left-hand index column. That's the fastest and most effective way to get information about the tutorials to the people who manage that part of the site. Could you post a message asking for a little more clarification of R6 and R7, plus a link to this thread please?

1chicagodave
 
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Re: USBTiny will not communicate with MCU

Post by 1chicagodave »

Wow! What a difference.

Thanks for posting scope results. It's always nice to see what's really happening on that level.

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plc_gremlin
 
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Re: USBTiny will not communicate with MCU

Post by plc_gremlin »

k. I have posted feedback over on the learning system side of the site and pointed them to this post. Thanks for recommending that.
The voltage on those MISO/MOSI signals was much lower before putting the R4/R7 resistors in. Very strange but its working now so :D .

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