introduction

Overview

The Weensy 3.6 board is a breakout board and I/O expansion for the Teensy 3.6 from PJRC. It provides the following

features

features:

Open Hardware design based on Creative Commons 4.0 license
Single 5V power supply input connector (screw terminals); provides 3.3V for Teensy 3.6 and other peripherals.
LED indicates when power is applied.
Adafruit-compatible Feather bus (compatible with software written for the feather adapter for the Teensy 3.2).
Two MCP23S17 GPIO expansion chips provide 24 I/O lines (presented on two PPDIO96-compatible 20-pin headers) and eight DIP switches.
PPDIO96 compatible connectors support PPOPTO-12 opto-isolator and PPRLYIO-12 relay-based input boards.
Eight PWM-compatible digital output lines are routed through a ULN2308 darlington array (high-current, 500ma/pin).
Eight Teensy 3.6 GPIO pins are brought out to a header through a 5V level shifter.
Watchdog timer actuates a relay after five-second timeout without a refresh operation (timeout period can be changed by swapping out a different resistor).
An LED indicates current watchdog timeout state.
Watchdog state (relay) is available on a three-pin header (relay NO, COM, and NC contact signals).
An LED indicates when the watchdog timer is being refreshed.
3.3V level shifting (from Teensy 3.6) to 5V for many I/O pins.
RS232 level shifting (from TTL to RS-232 levels) for one RS-232 serial port (using Sparkfun Max3232 or FTDI cable).
I2C level shifting for two I2C ports (one of which is multiplexed to eight ports).
Provides 8 independent I2C ports (routed to four six-pin headers on the board).
I2C expansion bus connectors support PPAIO-16/4 analog I/O boards (as well as PPAC-4 and PPAC420 analog conditioning boards).
SPI bus expansion with eight independent chip select lines (routed to two headers on the board -- PPDIO96 bus and PPDO bus; note: one CS line controls the two on-board MCP23S17 GPIO expanders).
PPDIO96-compatible bus supports up to six PPDIO96 digital I/O boards (96 digital I/O lines/board, up to 576 additional I/O lines!).
PPDO-compatible bus supports up to 10 PPRelay-12 and/or PPSSR-16 relay/digital output boards.
Headers for Teensy 3.6 analog input (ADC) ports.
Headers for Teensy 3.6 analog output (DAC) ports.
Headers for Teensy 3.6 USB Host port.
Full buffering for output signals.
Interrupt support for digital input devices.
Test pins for various important signals are present on the PCB.
Software-controlled reset line for resetting peripherals.
Watchdog state is also broadcast to all peripheral boards.
Schematic and board layout are available in Eagle format.
DIN rail brackets are available in .STL format for 3D-printing.

technical details

The Weensy 3.6 board provides the following functionality:

Almost all pins on the Teensy 3.6 are brought out to various connectors or circuits on the Weensy 3.6 board.
Adafruit Feather compatible bus - Electrically identical to the Teensy 3.2 Feather adapter from Adafruit.
Level shifting: The Weensy 3.6 board converts 3.3V logic levels to the 5V logic levels for all external connections (except Feather interface bus which is 3.3V).
I2C level shifting: The Weensy 3.6 board converts I2C signals on two of the three I2C busses brought out from 3.3V and 5V (note: the I2C bus on the Feather interface bus operates at 3.3V as per the Feather specs).
Two SPI busses available: one on the Feather interface bus and one providing a DAQ_IF-compatible PPDIO96 and PPDO SPI expansion bus.
SPI bus expansion: The Weensy 3.6 board expands the SPI chip-select line to eight separate board select lines (BS0, BS1,..., BS7).
I2C bus expansion: The Weensy 3.6 board contains an Adafruit TCA9584 I2C bus multiplexor breakout board that expands one of the I2C busses to eight separate I2C busses (allowing you to attach up to eight devices with the same I2C bus to the Weensy 3.6 board).
RS-232 level shifting: The Weensy 3.6 board includes a Sparkfun Max3232 breakout board that converts TTL-level RS-232 signals to true RS-232.A DB-9 DTE connection is provided on the Weensy 3.6 board.
FTDI support: In place of the MAX3232 module, you can optionally install an FTDI serial-to-USB cable. Note: only one of the MAX3232 module or FTDI cable may be installed on a single Weensy 3.6 board. Installing both of these devices will create conflicts that could damage the modules or the Weensy 3.6 board.
Five second watchdog timer with SPDT NC/COM/NO (normally closed/common/normally open) relay. Useful in safety critical systems to detect when the software has frozen. Hardware can automatically reset itself or place the system in a fail-safe mode when a watchdog timeout occurs. Timeout is nominally 5 seconds but you can easily change it by substituting a different resistor value.
Buffering for all output signals (including SPI outputs).

In addition to the above, the Weensy 3.6 board features LEDs indicating the following: