what are the pads under teensy 3.1 board?

[doughboy]

What are the pads under the teensy 3.1 board for? There are pads for reset and D- and D+, but I see 6 more unlabelled pads.

 

[doughboy]

Also, do I only need to connect VUSB, D+, D- and GND to a usb connector and I can connect a computer usb to that and upload program, etc? What about the connection to the 5th line (usb pin4 in schematic) ?

 

[robsoles]

Answering #2 first: Provided you connect correctly, yes, you can wire your own USB connection using those pads. Pretty sure 5th line is effectively for (at least simile of) chassis GND but I should probably review the schematic in question, maybe even consult my favourite EE, before saying that.

The unlabelled pads are used during programming and testing on Paul's bed of nails tester, pretty sure.

'Reset' does what it says, pulling it low will cause the MCU to restart.

 

[HWGuy]

Pin 4 from the USB Micro is the ID signal. It is used for the USB Host mode/OTG, but currently not supported by the Teensy 3.1. Pin 4 can be left floating. The USB A Plug has only 4 Pins (VCC,DM,DP,GND) and no ID Pin.

How to repair a broken-off Teensy 3.0 USB connector


USB ID is one of the unlabeled pads:



The other unlabeled pads are for programming the MINI54 (ICE_CLK, ICE_DAT, /RESET) and from the K20: VDDA, VREGIN.

 

[PaulStoffregen]

If you look at the schematic, you'll see those test pads are indicated as little dots on the ends of wires.

http://www.pjrc.com/teensy/schematic.html

The unlabeled ones are used during testing. We test every Teensy on a bed-of-nails test fixture. Spring loaded "pogo" pins touch each pad. The tester checks connectivity to all locations and lots of other stuff. Except for the USB connector, connectivity to every part of the board is tested.

Here's some info about the tester, from the Kickstarter when we launched Teensy 3.0 a few years ago.

https://www.kickstarter.com/project...rm-cortex-m4-usable-in-arduino-a/posts/305527

Teensy 3.1 has one more test pad, so a whole new bed of nail test fixture was made for 3.1. It looks pretty much identical to the older one in those photos.

Later in another test, we actually plug each Teensy in to USB cable and program the LED blink. That test verifies the USB connector, pushbutton and LED, which can't be tested by the bed of nail.

 

[doughboy]

Thanks for the replies.

Any suggestions on how to cover up the unlabelled pads so there are no exposed contacts?
I don't really want to get solder mask paint unless that is the only option.

I'm thinking of using this technique
https://forum.pjrc.com/threads/2607...ns-with-a-socket?p=52894&viewfull=1#post52894

to connect the D+ and D- to a pin header without using specialized pogo pin, just like how it was done for the reset pad.
The D- will have one unlabelled pad in contact, and D+ has 2 pads that I need to cover/insulate from the pin header.
So the paint must be able to withstand 300C soldering iron heat.

Thanks!

 

[pictographer]

Cover the exposed contacts with Kapton tape?

 

[doughboy]

Cover the exposed contacts with Kapton tape?

yeah, I found that on google search. I suppose I can either buy a roll of kapton tape or 5ml solder mask paint, they are both $0.99 each on ebay.
I'm just not sure if the added thickness of the tape will be a problem.

 

[doughboy]

I'll try kapton tape first. its 2.3mils thick and I don't have to deal with curing the solder mask paint in UV sunlight.

 

[robsoles]

...

'Reset' does what it says, pulling it low will cause the MCU to restart.

I can't see where this got corrected so I better correct myself this time: Pulling reset low halts the processor, releasing (or driving back high) the reset line will cause the processor to restart.