New 4.2 Pi Zero W build won't boot

Kai G

New member
I soldered everything up today. My solders certainly aren't pretty, but I can't find anything obvious bridged or gapped. Pictures here:


When I mated my Pi Zero W and plugged in 12V I got green and yellow LEDs initially and a black bar on the upper line of my LCD. After about 5 minutes it hadn't progressed or connected to my WiFi, so I power cycled it. After that the LEDs would turn off, but still no display or wireless connection. Powering the RPi from a micro-USB gave the same results. I noticed the RPi is running very hot to the touch, but I'm not sure what's normal there. I tested the voltages for the Pi socket and had 5V on the first two 5V pins, 3.3V only on G25, and 1.15V on TXD, RXD, MOS, SCK while plugged into 12V. Should the 3V3 at pin 1 also have voltage?
On the software side I've tried both the stable and snapshots from the download page. I also tried the HeaterMeter AP image, which also failed to boot.
Although I don't have a specific reason to doubt it the RPi is a suspect; it's a 2017 model that I've had in a drawer for quite a while. I've ordered a new one and I'll have the display adapter to watch in a few days.
Any other ideas or things to try?
Thanks for any help.
 

KeithC

New member
I would clean the board with 91% rubbing alcohol & cotton tips. I had a short on the mosfet for some reason that started smoking. cleaned it and it stopped. I was also missing the processor, like a dummy lol. make sure you got the correct power brick too, should be like 12v 2a output. also check the contrast on the display, make sure it's not turned up too high. The older models look like they can take some time to boot up, so wait a few mins and check http://heatermeter.com/devices/ to see if it's visible at all. all else fails, maybe do a check, make double sure none of the components are backwards.
 

KeithC

New member
one more thing: which way does the Pi install on these? I didn't see it in the installation instructions, but may have missed it. ensure it's not upside down.
 

Steve_M

TVWBB Guru
the pi zero w should be mated up to the HM 4.2 board so that the side with the SD card slot is closest to the HM temp probe jacks.

If the pi is really hot, it's possible that it's damaged
 

Kai G

New member
the pi zero w should be mated up to the HM 4.2 board so that the side with the SD card slot is closest to the HM temp probe jacks.

If the pi is really hot, it's possible that it's damaged
I watched CapnBry's YouTube video about firmware install, so I'm fairly certain I got it on the correct direction. I tried to use the same RPi Zero on a previous project, which never worked right. At the time I figured I was messing something up, but now there's another data point that may indicate a bad Pi. I do have a RPi3, but with the 4.2 board I can't use it to test without clipping some header pins which I don't want to do, so I'll wait a week until my new Zero shows up and give it another shot.
In the mean time I'll take KeithC's advise and clean the board with rubbing alcohol.
 

Kai G

New member
I would clean the board with 91% rubbing alcohol & cotton tips. I had a short on the mosfet for some reason that started smoking. cleaned it and it stopped. I was also missing the processor, like a dummy lol. make sure you got the correct power brick too, should be like 12v 2a output. also check the contrast on the display, make sure it's not turned up too high. The older models look like they can take some time to boot up, so wait a few mins and check http://heatermeter.com/devices/ to see if it's visible at all. all else fails, maybe do a check, make double sure none of the components are backwards.
Does it require 2A output? The brick I'm using is only 1A, which is what I thought I remembered being required. I did try hooking up the RPi to a USB power adapter and that didn't give me any different results. I was under the impression that, without the blower or probes attached, current shouldn't be an issue.
 

Bryan Mayland

TVWBB Hall of Fame
You shouldn't need a 2A power supply, 1A is plenty, 500mA would be ok without a blower or servo attached, and like 100mA is all you need to just run the HeaterMeter board by itself. You should see 3.3V at the VCC pin on the header labeled FTDI, but the two 3V3 pins on the Pi connector are not connected to anything. With just the HeaterMeter plugged into 12V nothing on the board should be at all warm to the touch. It should just be room temps. Checking your board it looks like at least all the major components are installed properly and the soldering looks pretty good. There's a board image here that might assist in checking connection but zeesh I designed this board and it is hard to follow what goes where:

Verify these pins are connected and also that they are NOT connected to any adjacent pin:
ATmega Pin 19 - SCK on Pi Header
Pin 18 - MIS
Pin 17 - MOS
Pin 1 - G25

If that checks out then have you tried accessing the webui to make sure the Pi is booting?
 

KeithC

New member
Does it require 2A output? The brick I'm using is only 1A, which is what I thought I remembered being required. I did try hooking up the RPi to a USB power adapter and that didn't give me any different results. I was under the impression that, without the blower or probes attached, current shouldn't be an issue.
sorry, thought it took more than that for some reason... thanks @Bryan Mayland for setting that straight lol
 

Kai G

New member
You shouldn't need a 2A power supply, 1A is plenty, 500mA would be ok without a blower or servo attached, and like 100mA is all you need to just run the HeaterMeter board by itself. You should see 3.3V at the VCC pin on the header labeled FTDI, but the two 3V3 pins on the Pi connector are not connected to anything. With just the HeaterMeter plugged into 12V nothing on the board should be at all warm to the touch. It should just be room temps. Checking your board it looks like at least all the major components are installed properly and the soldering looks pretty good. There's a board image here that might assist in checking connection but zeesh I designed this board and it is hard to follow what goes where:

Verify these pins are connected and also that they are NOT connected to any adjacent pin:
ATmega Pin 19 - SCK on Pi Header
Pin 18 - MIS
Pin 17 - MOS
Pin 1 - G25

If that checks out then have you tried accessing the webui to make sure the Pi is booting?
I cleaned the board, checked the pins, and reflowed a couple, but no dice. The Pi is too hot to touch after a couple of minutes and no WebUI loads, so I think that's my primary suspect. Should the WebUI load if I just boot the Pi disconnected from the HM board? My replacement Pi Zero is here in a few days, so I'll give that shot.
For voltages I'm getting 3.3V on both G25 and the VCC pin. Is that ok for G25?
I also reseated the Atmega chip and I got a single green light instead of the green/orange combo I have been seeing. No WebUI or display after 3-4 minutes, so I unplugged it. Is there any diagnostic value to the LEDs or are they only useful after the RPi software loads?
 

Bryan Mayland

TVWBB Hall of Fame
  • 3.3V is good on G25
  • The webui should load regardless of if there is a HeaterMeter connected, it just won't have any data in the graph
  • The LEDs don't mean anything unless the ATmega is flashed with HeaterMeter, which happens on boot of the Pi (if it can)
  • The LED on the Zero should show the boot progress. Blinking like crazy as the kernel loads, then blink fast (preinit), then slow (services starting), then go steady (usually off on the Zero) to indicate it has fully booted and is ready to do webstuff.
 

Kai G

New member
I've got another Zero, but no extra headers, and removing already soldered headers seems like it'd be a giant pain, so I'll wait a couple of days for my new Pi to show up to fix it. I did just throw the SD card in my spare Pi and it immediately connected to my network no problem, so I guess that settles it. I'm mad I didn't think to test that earlier.
Thanks for the quick replies and the awesome product. I can't wait to use it. I'll post here again when it's working, but I think we can call this likely solved.
 

Kai G

New member
  • 3.3V is good on G25
  • The webui should load regardless of if there is a HeaterMeter connected, it just won't have any data in the graph
  • The LEDs don't mean anything unless the ATmega is flashed with HeaterMeter, which happens on boot of the Pi (if it can)
  • The LED on the Zero should show the boot progress. Blinking like crazy as the kernel loads, then blink fast (preinit), then slow (services starting), then go steady (usually off on the Zero) to indicate it has fully booted and is ready to do webstuff.
Quick question, are all 26 pins the instructions call for actually needed? I've got 21 pins leftover and if I can skip 5 pins I can try it now.
 

Bryan Mayland

TVWBB Hall of Fame
Quick question, are all 26 pins the instructions call for actually needed? I've got 21 pins leftover and if I can skip 5 pins I can try it now.
Yeah it really just needs: 5V, GND, RX, TX, MOSI, MISO, SCK, and G25. So two blocks of 2x5 (4* 1x5) pins is all you need. (All the GNDs don't need to be connected, just get one on each end and it should be fine)
 

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