Heatermeter 4.3 not recognized by pi


 
there's been a bit of discussion and troubleshooting of the avr fuse error here, search the forum and maybe those threads will offer insight. Did you verify your 3.3v regulator is putting out 3.3vdc and it is getting to the ATmega?
 
Ralph, yes i am reading through them now. yes i verified 3.3v at regulator and at the ATmega. it seems like the rpi is not seeing the HM board. what pins do i need to be concerned with on the 26 pin connection ?
 
i went through the posts and all of them are talking about a regulator in the wrong position. I am 100% certain mine is in the correct position. i even swapped out the atmega just in case and the same thing occurs. all voltages seem correct and i verified tx and rx from the atmega to the 26 pin connector.
 
I had a bad RasPi that the SPI bus was pooched on. It could communicate with the Atmega, but not program it. See my thread on it here.

I looked at the pics of your board again and the only thing I'd suggest is giving it a good scrub with some 99% isopropyl alcohol and a toothbrush. There looks to be lots of rosin on the board and it can cause problems.
 
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Steve, funny you should say that. i tried a second rpi3 and same results. i will give the board a good cleaning and see what happens
 
still nothing from the atmega. anyone willing to let me send them the board and see whats going on? i am at a loss.
 
I was looking over a few of my pics and noticed that 1 of my capacitors (directly across from BFB on ATmega) may need a reflow as it doesn't look like solder went all the way through. Now i have reflowed most of the board after this picture was taken, so i am not sure if it is still in the same condition. I will have to check when i get home from work. Could that be a cause of why my ATmega is not flashing?
 
Last time I looked the schematic image for the v4.3 was not as accessible as the v4.2, but the circuits are by and large the same... The connections between the rPi and the ATmega are certainly the same.

Here is the schematic:

HeaterMeterPi.png


As you can see, on the ATMega you are looking at pins 1,2,3,17,18,19 going to the rpi header along with 5v and gnd in a few places...

On the atmega you can see VCC of 3.3v applied to pins 7 & 20, and cap C1 is the filter cap, also note the (3 pin) oscillator is important to the function of the ATMega.

You can check continuity on this stuff if you want to poke at it a little more before you send it off.
 
The 4.3 schematic is here and the LCD / Button board is here.

The nice thing about the heatermeter is that when you boil it down, there's not too many parts on on the HM board. Figuring out which part is bad can be time consuming, but if you have an interest in getting your feet wet with electronics, it's pretty user serviceable with most of the parts being through hole and having easy access to the schematics and the forum.
 
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Steve and Ralph, by the time i got to read your posts i had already shipped the device to John. He should have it by thursday. Thank you guys for the help. i learned a lot in the past few days!

John, FYI your mailbox is full. :)
 
To give an update on this issue.

I found the problem(s), as I'm not sure if it was just one or two issues.

When I plugged it in nothing happened, but the Rpi was working fine.

I probed the board for shorts on the atmega and all looked ok and then I looked at the Rpi header and I found that the Gnd and Sck where shorted together. I used my heated solder sucker(I love that thing) and my hot air desolder station and removed the header and replaced it with a new one. So no more short on that.

Then I plugged in the heatermeter and then I had smoke coming from the Mcp1700. So, I removed that as it to had a short between GND and one of the other legs. Put in a new one and all was good, the atmega programmed and I was able to log into the HM and change the settings.

It helps to have a multimeter that has a good continuity checker that beeps, makes finding shorts pretty easy for the most part.

John
 
Nice work, John! I guess we need to add that to the troubleshooting script: "With no power and no Pi connected, make sure there is NO continuity between any two consecutive Pi pins on the header (apart from the two 5V pins)"
 
Nice work John! Having a multimeter and knowing how to use it to check for continuity and shorts is the most basic and valuable tool for troubleshooting issues like this... or in some cases, just using a magnifier to look closely at the solder work will do the trick. Seems to me a short in either of those places would cause the flashing of the ATMega to fail.
 
The short was under the header and would not have been visible and the same on the mcp1700. In this case to much solder flowed to the other side of the board and shorted out
 
Sometimes a solder sucker can suck enough solder through the hole to clear shorts on the other side, or using solder wick with the board sitting in the orientation where gravity will help the flow can work too. At any rate, glad you got it worked out for the OP.
 
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