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ergodox-firmware/src/keyboard/controller/teensy-2-0.md

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Documentation : Teensy 2.0

Pinout and Pin assignments

  • + indicates connected pin
  • o indicates unconnected pin
  • = is used to list other things the pin is connected to
  • -s inserted between some of the pin functions for readability
  • OC** pins enclosed in parenthesis had lines over them in the pinout

Teensy 2.0

                          GND +---.....---+ Vcc
                       SS PB0 +           + PF0 ADC0
                     SCLK PB1 +           + PF1 ADC1
                     MOSI PB2 +           + PF4 ADC4
                     MISO PB3 +  +     +  + PF5 ADC5
RTS  OC1C  OC0A --------- PB7 + PE6  AREF + PF6 ADC6
           OC0B  INT0 SCL PD0 + AIN0      + PF7 ADC7
                 INT1 SDA PD1 + INT6      + PB6 ADC13 OC1B  OC4B
RXD1 ----------- INT2 --- PD2 +           + PB5 ADC12 OC1A (OC4B)
TXD1 ----------- INT3 --- PD3 +           + PB4 ADC11
     OC3A (OC4A) -------- PC6 +           + PD7 ADC10 T0 -- OC4D
ICP3 ----- OC4A --------- PC7 +-+-+-+-+-+-+ PD6 ADC9  T1 - (OC4D) onboardLED
                 CTS XCK1 PD5 --/ | | | \-- PD4 ADC8 ------------ ICP1
            Vcc ------------------/ | \-------------- RST
            GND --------------------/

Teensy 2.0 Pin Assignments

          power_negative  GND +---.....---+ Vcc  power_positive
                column_7  PB0 +           + PF0  row_5
                column_8  PB1 +           + PF1  row_4
                column_9  PB2 +           + PF4  row_3
                column_A  PB3 +  o     o  + PF5  row_2
            (OC1C) LED_3  PB7 + PE6  AREF + PF6  row_1
             (SCL)   I2C  PD0 +           + PF7  row_0
             (SDA)   I2C  PD1 +           + PB6  LED_2 (OC1B)
                column_B  PD2 +           + PB5  LED_1 (OC1A)
                column_C  PD3 +           + PB4  = Vcc
                column_D  PC6 +           o PD7
                          PC7 o-o-o-o-o-o-+ PD6  onboardLED = GND
                          PD5 --/ | | | \-- PD4
                          Vcc ----/ | \---- RST
                          GND-------/
  • notes:
    • Row and column assignments are to matrix positions, which may or may or may not correspond to the physical position of the key: e.g. the key where row_4 and column_2 cross will be scanned into the matrix at [4][2], wherever it happens to be located on the keyboard. Mapping from one to the other (which only matters for defining layouts) is handled elsewhere.
    • LEDs are labeled using numbers (starting with '1') instead of letters (starting with 'A') as on the PCB.
    • SCL and SDA: Need external pull-up resistors. Sometimes the Teensy internal pull-ups are enough (see datasheet section 20.5.1), but i think for this project we'll want external ones. The general recommendation for 400kHz I²C seems to be 2.2kΩ.

Notes about Registers

General I/O (see datasheet section 10.2.1)

DDRxn  function  PORTxn  function
1      output    1       drive high
                 0       drive low
0      input     1       internal pull-up on
                 0       internal pull-up off

PINxn  action   function
       write 1  toggles the value of PORTxn
       read     returns the logical value (1|0) of the pin

PWM on ports OC1(A|B|C) (see datasheet section 14.10)

  • notes: settings:

    • PWM pins should be set as outputs.
    • we want Waveform Generation Mode 5
      (fast PWM, 8-bit)
      (see table 14-5)
      • set TCCRB[4,3],TCCRA[1,0] to 0,1,0,1
    • we want "Compare Output Mode, Fast PWM" to be 0b10
      "Clear OCnA/OCnB/OCnC on compare match, set OCnA/OCnB/OCnC at TOP"
      (see table 14-3)
      this way higher values of OCR1(A|B|C) will mean longer 'on' times for the LEDs (provided they're hooked up to GND; other way around if they're hooked up to Vcc)
      • when in a fast PWM mode, set TCCR1A[7,6,5,4,3,2] to 1,0,1,0,1,0
    • we want "Clock Select Bit Description" to be 0b001
      "clkI/O/1 (No prescaling)"
      (see table 14-6)
      • set TCCR1B[2,1,0] to 0,0,1
      • LEDs will be at minimum brightness until OCR1(A|B|C) are changed (since the default value of all the bits in those registers is 0)

  • notes: behavior:

    • The pins source current when on, and sink current when off. They aren't set to high impediance for either.
    • In Fast PWM mode setting OCR1(A|B|C) to 0 does not make the output on OC1(A|B|C) constant low; just close. Per the datasheet, this isn't true for every PWM mode.

  • abbreviations:

    • OCR = Output Compare Register
    • TCCR = Timer/Counter Control Register

Copyright © 2012 Ben Blazak benblazak.dev@gmail.com
Released under The MIT License (MIT) (see "license.md")
Project located at https://github.com/benblazak/ergodox-firmware