Understanding D4 Led on Teensy 4.0

M

MeatySteak

Member
Hi,

I'm trying to understand the teensy 4.0 deeper and having been trying to wrap my head around the D4 led.

According the schematic, it seems to come from 3.3V power, into the led and then into the R2 Resistor then into the PTB3 pin on U2 (MKL02Z32VFG4). However, I've been following the tracks on the teensy itself, (diagrams and a physical board as well), and it seems to suggest that 3.3v power goes from a via into the led, then through another via again into nothing? Or potentially ground? Either way, there is no point (that I can see) where the led is in series with the R2 resistor? Which doesnt make sense which is why I am here.

I dunno maybe I'm just stupid or cant see but I'm at a standstill here. I attached photos of where I think the nets are, green for the resistor and red for the led. This is what I see and as you can maybe understand, why I see that there is no connection between the two.

All help is appreciated!
Thanks
 

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Teensy 4.0 is a 6 layer PCB. You're only seeing 2 of the 6 layers in these images.

The trace you're not seeing is on layer 3. Here's a peek at that layer and the specific trace which completes the red LED connection.

1756688676557.png


I should probably mention these are all images of the PCB design before the 2023 chip shortage which forced us to change the U2 and other parts and make minor edits to the PCB layout. The latest PCB shipping since 2024 has all the traces of this LED on the top and bottom layers.
 
Last edited:
PaulStoffregen said:
Teensy 4.0 is a 6 layer PCB. You're only seeing 2 of the 6 layers in these images.

The trace you're not seeing is on layer 3. Here's a peek at that layer and the specific trace you're not able to see.

View attachment 38118

I should probably mention these are all images of the PCB design before the 2023 chip shortage which forced us to change the U2 and other parts and make minor edits to the PCB layout. The latest PCB shipping since 2024 has all the traces of this LED on the top and bottom layers.
Click to expand...
Ahhhh 6 layers. Gotcha, is there somewhere I can see these traces? Especially the updated ones? Or is that protected information?

Follow up to that, how recent is the schematic on the teensy page? I know the BAT54Cs were replaced so it at least hasn't taken into account that.
 
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