Custom teensy board won't program

[shreedee]

I designed a custom board using the Teensy3.1 Schematics. But it will not program, The MCU reset pin (34) is always showing .1 Volts.
Trying to debug, I realized that the EZP_CS pig (26) is NOT connected, instead the MINI45TAN is connected on pin 25 ( and other EZPORT pins). How is Teensy supposed to get in EzPORT mode for the MINI54TAN to program it.

Can you send some guidance please.

 

[robsoles]

When one of the PCB layout 'artists' at work does that, including me (happen's to the best of us ), we can only cut tracks and place link wire.

If Paul has a remedy for this that he can just post I will be really really impressed, not that I'm not already pretty impressed anyway

It is a harsh lesson at times but before having PCBs cut/made, or making them ourselves, we simply must check all connections in our schematics very very carefully and then when we are doing the PCB layout we must check all nets are connected as planned in the schematic.

 

[PaulStoffregen]

I received this exact same question in email today, and already answered it.

Normally I check the forum first....


Edit: a reply came that the problem turned out to be power related.

 

[texane]

Hi Paul,

I am also interested to know why the EZP_CS is not connected. As I
understand it, the MINI54TAN uses the EZPORT to program the MCU
flash. How can it work if EZP_CS is left floating ? Could you post the
reply you sent by email here ?

Thanks !

 

[Constantin]

Or, go down the path of using chip holders and breadboarding the whole assy first. I'm pretty impressed with how inexpensive some of these socket test units have become.

The various flavors of the Teensy bootloader or MCU chips can be held by test sockets with dip interfaces that 'only' cost about $75-100 at ebay (for example, search for QFN32 socket, then drill down to a 5x5mm edition that can breadboard the middle of the two chips shown on the Mini54 page). The LC uses a QFN48 @ 7x7mm, whereas the Teensy 3.x MCUs are at home in a 64-LQFP package.

I am thinking of buying one or two just so I can confirm that everything works as expected with the Teensy bootloader with any new layouts/schematics I may consider. Much easier to modify a breadboard than a fabricated PCB. One or two borked layouts later and the thing will have paid for itself. Granted the capacitances, etc. will be different vs. a real PCB but at least most electrical connections can be tested.