Overview and Warning:

This library was originally created to experiement with the FlexIO capabilities of the new Teensy 4 board and will also support the Teensy 4.1

This program is free software: you can redistribute it and/or modify it

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Details on FlexIO

See chapter 49 of the IMXRT1060RM manual which you can download from the PJRC website: https://www.pjrc.com/teensy/datasheets.html

There are more discussions about FlexIO up on the PJRC forum, including: https://forum.pjrc.com/threads/58228-T4-FlexIO-Looking-back-at-my-T4-beta-testing-library-FlexIO_t4

FlexIO pins on T4 and T4.1

The Teensy 4 (ARDUINO_TEENSY40) has the following Flex IO pins defined:

Note: I have these tables in Teensy pin number order, It may also be interesting to also have a version with FlexIO pin order, as at some point I will experiment with parallel pin IO..

FlexIO 1 - The three rows are: Teensy pin, Flex IO pin, and MUX setting for that pin:

    2,       3,    4,    5,  33,
    4,       5,    6,    8,  7, 
    0x14, 0x14, 0x14, 0x14, 0x14

Ranges: 4-8

FlexIO 2

    6,       7,    8,    9,  10,    11,   12,   13,   32, 
    10,     17,   16,   11,  0,      2,    1,    3,   12, 
    0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 

Ranges: 0-3, 10-12, 16-17

FlexIO 3 - Note Flex IO 3 does not have DMA support

    7,       8,   14,   15,   16,   17,   18,   19,   20,  21,    22,   23,   26,   27,   
    17,     16,    2,    3,    7,    6,    1,    0,   10,   11,    8,    9,   14,   15,    
    0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19,

Ranges: 0-3,6-11,14-17

The Teensy 4.1 (ARDUINO_TEENSY41) Will have additional IO pins.

FlexIO 1 - The three rows are: Teensy pin, Flex IO pin, and MUX setting for that pin:

    2,       3,    4,    5,  33,    49,   50,   52,   54
    4,       5,    6,    8,  7,     13,   14,   12,   15
    0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14

Ranges: 4-8,12-15

FlexIO 2

    6,       7,    8,    9,  10,    11,   12,   13,   32,   34,   35,   36,   37
    10,     17,   16,   11,  0,      2,    1,    3,   12,   29,   28,   18,   19
    0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14

Ranges 0-3, 10-12, 16-19, 28-29

FlexIO 3 - Note Flex IO 3 does not have DMA support

    7,       8,   14,   15,   16,   17,   18,   19,   20,  21,    22,   23,   26,   27,   34,   35,   36,   37,   38,   39,   40,   41
    17,     16,    2,    3,    7,    6,    1,    0,   10,   11,    8,    9,   14,   15,   29,   28,   18,   19,   12,   13,    4,    5 
    0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19 

Ranges: 0-19, 28-29

The Teensy Sparkfun MicroMod (ARDUINO_TEENSY_MICROMOD) is sort of a cross between T4 and T4.1, but has additional pins on FlexIO 2

FlexIO 1 - The three rows are: Teensy pin, Flex IO pin, and MUX setting for that pin:

    2,       3,    4,    5,  33,  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
    4,       5,    6,    8,  7,   0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
    0x14, 0x14, 0x14, 0x14, 0x14, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,

Ranges: 4-8

FlexIO 2

    6,       7,    8,    9,  10,    11,   12,   13,   32,   40,   41,   42,   43,   44,   45,
    10,     17,   16,   11,  0,      2,    1,    3,   12,    4,    5,    6,    7,    8,    9,
    0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14, 0x14,

Ranges 0-12, 16-17

FlexIO 3 - Note Flex IO 3 does not have DMA support

    7,       8,   14,   15,   16,   17,   18,   19,   20,  21,    22,   23,   26,   27, 0xff,   
    17,     16,    2,    3,    7,    6,    1,    0,   10,   11,    8,    9,   14,   15, 0xff,    
    0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0xff,

Ranges: 0-3,6-11,14-17

Library details

FlexIOHandler

The top level class in this library is the class: FlexIOHandler, which tries to do some limited resourse management. Like mapping an IO pin to which FlexIO object is is on and the actual item on that flexio object. It also then allocates other resources like timers and shifters.

There are also a few methods to help with the CCM (Clock Management), for example:

    uint32_t computeClockRate();

Returns the speed that the specified FlexIO is running at, which is controlled by registers in CCM. Default is 480M/16 or 30000000

You can update this with the method:

    // clksel(0-3PLL4, Pll3 PFD2 PLL5, *PLL3_sw)
    // clk_pred(0, *1, 2, 7) - divide (n+1)
    // clk_podf(0, *7) divide (n+1)
    // So default is 480mhz/16
    void setClockSettings(uint8_t clk_sel, uint8_t clk_pred, uint8_t clk_podf);

The main reason for the desire to for example allow slower baud/clock rates with the SPI and Uart code.

For example with the FlexSerial object, the Baud divider is one byte so without updating the clock speed So the default of 30000000 and max divide by 256 = min Baud of 117,187.5/ 2 = 58,594 Now setting the pred to 7 your minimum baud reduces to: 29296.875 / 2 about 14,648

Future Updates

Again WIP