Mike's Build Log

Finally. Put together the header this week. And of course I have an issue right away. Plugging in the Sensor Board the LEDs light up right away. I’m guessing I got something wrong on the board layout. I didn’t quite do what Chris did with the layout. I’ll post an image of my PCB but it might take a bit tonight.

I pushed my repo https://github.com/mfrith/CE-Header. It’s mostly Chris’s work with my take on the SensorBoard layout.

Where does U3 get it’s 3V3 supply?

Off pin 12 on the header. U3 has two 3V3 pins, 10 and 16 and I think I have both connected.

Pin 10 is the clear input which is being held high but it does not actually supply power. Pin 16 should be supplying power but in the image you posted it seems to go to a via that misses the 3V3 track on the other side of the board, unless there is a track on the other side not visible in the image. Have measured voltages on the board? It is unfortunate that the clear pin (10) is tied directly to 3V3 otherwise you could temporarily connect it to ground to see if the chip reset.

I haven’t measured voltages yet. Re 3V3, the via near pin 10 connects to pin 16.

I am just curious if you have both CE_Header connectors on the top side of both boards. i.e. I realised an issue when connecting the header on another project and posted about it on the CE Header Footprint thread.

Hi Steve, I put the CE Header on the top of both boards but that doesn’t mean I didn’t mis-connect it. :slight_smile:

Humor me and double check that the 5v (pin 1) on the CE_Header on the teensy adapter board mates with what you expect the 5v pin is on your sensor board.

For measurements, pin 12 on the CE header to ground side of the cap near pin 16 on the register is 3.26 V. From 1 through 7 across the LED is 2.17 . Touching some of the pins causes some of the LEDs to switch off. Hmmmm

Pin 1 on the Teensy board is 5V? You mean the Teensy Converter?

That’s the converter, pin 26 from the Teensy goes in the top left spot. My Teensy is upside down compared to the converter and sensor boards.

Yes Mike, I was referring to the 5V pin CE_Header on Teency adapter board should match with the 5V pin on your sensor board (I have corrected my question). If the CE_Header is modelled, on the layout, on the top side and soldered onto the top side of the respective boards, then there will be a problem. If one of the headers is soldered on the bottom side of one of the boards, then all should be OK.

Thanks Steve. Yeah this part confused me for a while. I watched the videos a lot

No luck trying to fix this issue, I think I’ll have to do the layout over.

And in the strange things you find dept, I just found a Digi Key order from two years ago that was not opened. :confused: What the …

I would diagnose the issue before doing another layout, if the issue turns out to be a problem at the schematic level then another layout won’t resolve it.

Have you tried writing any code to see if you can control the LEDs at all?

I agree with @1.21Gigawatts.

Another tip (from @hedrickbt) is to annotate the schematic with expected voltages and current. Then taking measurements at those points and try to understand why it is not behaving as expected.

Other things I would do…
Double check the symbols and their associated footprint pin outs with the datasheet for some of the active components. Even if they came from the KiCad library, does not mean they are 100% perfect in all cases.

Run the DRC to see if there are any anomalies on the schematic or layout.

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Thanks guys.

my diagnostic skills are still lacking.

I’m using Chris’s schematic from Github so I hope it’s not the problem. Though I did find an unconnected net label that took me a bit to find.

Yes, if I send a value the same three LEDs turn on, 3, 5 and 6 if I remember. Sending a second value never changes the LEDs, I have to unplug the Teensy to reset it. I thought this might be a clue but didn’t find anything, yet.

I did some quick checks but haven’t calculated all the output values.

Pin 10 shouldn’t be high when plugged in?


Pin 10 should be High - but is not the Vcc for the device. Pin 16 is Vcc. @1.21Gigawatts was asking where U3 gets its supply from. The Via near pin 10 is close to the Front Copper track so the connection is hard to see on the PNG.

I took a look at the KiCad files in your repo. There is one thing that I do see.
In Pcbnew, under Dimensions - Pads Mask Clearance, there is a Solder Mask Clearance of 0.2mm. I had an issue where this “default” setting started to expose the copper fill zone and caused some issues. I usually set this value to zero.

Your sensor board does not have any zone fill but your Teensy adaptor board does. Check that that the board is not exposing any more copper than it should. I have to admit, if this were really the issue, I would think there would have been other issues before this one.

What about the other devices on the sensor board? Are you able to read any values from those?

For the Light Dependant Resistor, you could unplug the Sensor board from the Teensy adapter and use the Ohm Meter on your DMM to measure the resistance across pins 15 and 16 of the CE Header. This just verifies at least that system is connected and behaving OK.

Going back to the Teensy board, have you connected a LED and resistor to any of the digital pins on the CE Header to get a “blinky” working? … just to prove that the Teensy adapter has no issues.

Thanks Steve,

I started to work on the other devices but didn’t have appropriate parts, they are on order.

I’m travelling for the next week so won’t have a chance to try your suggestions and hopefully the parts will be in when I get back.

Could it be a poor solder job by me? I noticed doing the soldering that my skill had deteriorated more than I expected, might have to move to 1206. :slight_smile: I’m tempted to put another board together to see if I can do a better job soldering and see if the same result happens.