Custom Teensy 4.1 part consolidation

[yeahtuna]

I'm wondering if I can safely replace R6 and R7 with 47k resistors?

 

[PaulStoffregen]

R6, yes.

R7, no. In fact, we changed this to 470K some time ago (but schematic wasn't updated) because 100K with the newer regulators was causing startup issues at lower input voltage, like under 4 volts.

 

[yeahtuna]

Thanks for the heads up. I'll replace R6 with 47K and R7 with 470K I guess.

 

[PaulStoffregen]

R7 is only needed during the 15 sec restore process. If you just leave R7 as an open circuit, everything except that restore process will work fine. Holding the button for 15 seconds will give the quick blink on the red LED, and if the button is released within the 4 second window, the hardware will simply reboot without changing the flash memory, rather than wipe the flash and write the known-good LED blink.

 

[yeahtuna]

I see. I will test, but it sounds like I don't need or want R7 in there. Thanks, Paul.

 

[yeahtuna]

I just tested and it programs just fine with R7 using both the button or with _reboot_Teensyduino_().

 

[yeahtuna]

Because my custom device will not be battery powered, I'm guessing I can simplify the following section:


This is what I've got right now, but I assume I probably don't even need that diode in there, and possibly other parts as well. What can I remove?

 

[yeahtuna]

Upon further reading, seems that diode is needed to keep the voltage on VDD_USB_CAP a step behind VDD_SNVS_IN. The 10uF capacitor doesn't provide enough delay on its own?