http://pjrc.com/teensy/K66P144M180SF5RMV2.pdf page 1338NOTE
An attempt to access an RTC register, except the access control
registers, results in a bus error when:
• VBAT is powered down,
• the RTC is electrically isolated, or
• VBAT POR is asserted.
from K66 reference manual:
http://pjrc.com/teensy/K66P144M180SF5RMV2.pdf page 1338
The Teensy startup code tries to access an RTC register.
It depends on the used crystals. With the crystals from reply#22:
16Mhz: 2x20pF
32kHz: none
no additional load capacitors neededFor example the crystal wants;
Here Paul recommends 20pF load capacitors for a 18pF crystal (Teensy 3.1): https://forum.pjrc.com/threads/27378-Teensy-3-x-Crystal?p=60672&viewfull=1#post60672
The 16MHz crystal on the Teensy 3.2, 3.5 and 3.6 has a load capacitance of 9pF.
no additional load capacitors needed
Paul recommends a 12.5pF crystal for RTC (Teensy 3.0): https://forum.pjrc.com/threads/724-...-3-0-RTC-questions?p=1561&viewfull=1#post1561
the load capacitors are calculated with this formula
CX = 2 * CL - CPARA - CINT
19pF = 2 * 18pF - 7pF - 10pF
- CX: external load capacitors
- CL: crystal load capacitance
- CINT: in microcontroller integrated capacitors
The Teensy core sets up the 16MHz crystal pins with a 10pF load: https://github.com/PaulStoffregen/cores/blob/master/teensy3/mk20dx128.c#L812
and the 32.768kHz crystal pins with a 20pF load: https://github.com/PaulStoffregen/cores/blob/master/teensy3/mk20dx128.c#L756- CPARA: Parasitical capacitance max 7pF
Think about it!Why a teensy 3.2,3.5 and 3.6 there are no capacitors in the crystals?
Why a teensy 3.2,3.5 and 3.6 there are no capacitors in the crystals?
They're built inside the chip. In fact, there's 4 capacitors inside the chip, 2pF, 4pF, 8pF and 16pF, which can be turned on/off by software control.
regarding the circuit in reply #24
have a look at the "Recommended connection for unused analog and digital
pins" section in the K66 datasheet. http://pjrc.com/teensy/K66P144M180SF5V2.pdf page 79 & 80
for example:
VREFH - Always connect to VDD potential
VREFL - Always connect to VSS potential
if there's going to be custom boards, we'll need the bootloader chips to be compatible with the k66 mcu (the pjrc page says it's only up to teensy 3.2)
They're built inside the chip. In fact, there's 4 capacitors inside the chip, 2pF, 4pF, 8pF and 16pF, which can be turned on/off by software control.
core_pins.h - Add in the info about the new pins (pin, mask, port register, ...), and counts - not hard but tedious.
pins_arduino.h - If you want some of them to work as Analog pins
pins_tensy.c - to add to bitband.
Hello,
i want to use in my project the function hibernate to have very little consumption.
I found this voltage regulator which has very low quiescent current but it's very low output current 85mA.
In my project i use two channels spi,three channels uart,three analog port,one channel i2c,sd card,one dac port and 24 io port,all peripherals and sd card powered from another voltage regulator.
The 85mA output current which gives is enough or i will need more??I use the teensy 3.6.