This library is provides an alternative interface to the usual pin access by pinMode, digitalWriteFast and digitalReadFast for Teensy ARM boards (T-LC up to T-3.6). The generated code is as efficient as calling the standard pin manipulation functions. Both methods can be used in parallel.
The following sketch shows the basic usage of the pin class
#include <pins.h>
using namespace pins;
pin<13> LED(OUTPUT); // Assignes the variable LED to pin 13 and switches its pin mode to OUTPUT
void setup(){
LED = HIGH; // Switch LED on
LED = LOW; // .. and off
LED.toggle(); // toggle LED
}
void loop(){
}You can also do things like
...
pin<0> SWITCH(INPUT_PULLUP); // Assume we have a switch attached to pin 0
pin<13> LED(OUTPUT); // LED on pin 13
...
void loop()
{
while(SWITCH == LOW){
LED.toggle();
delay(100);
}
}You can use the static interface of the pin class directly:
pin<3>() = HIGH;
pin<4>::toggle();
pin<5>::pinMode(OUTPUT_OPENDRAIN);
// in case you quickly want to set a pin for debugging something without first declaring it and setting its
// pinMode somewhere just do a
pin<28>(OUTPUT) = HIGH;Attaching an interrupt to a pin:
SWITCH.attachInterrupt(callback, RISING); Change pin properties:
LED.driveStrengthEnable(false); // which would be a bad idea of course...
pin<7>::slowSlewRateEnable(false); // enables full slew rate for the pinIf you need to change the pin assignment, e.g. you want to move Serial1 on a T3.2 from its standard pins 0 and 1 to the alternative pins 21 and 5 (those pins which are grayed out on the pinout cards) you can use:
pin<21>::setMUX(ALT3); // Set alternative function of pin21 to ALT3
pin<5>::setMUX(ALT3); // Set alternative function of pin5 to ALT3(see the datasheet for a list of possible alternative pin functions)
Reading and writing
LED = HIGH;
bool b = SWITCH; is as fast as digitalWriteFast() and digitalReadFast(). Toggling
LED.toggle();is faster than the usual
digitalWriteFast(13,!digitalReadFast(13));Paul has demonstrated how extremly fast digitalWriteFast() really is in this post: https://forum.pjrc.com/threads/41874-STRANGE-GPIO-speed-perfomance-with-digitalWriteFast()-(ring-oscillator-example)?p=132359&viewfull=1#post132359.
Here his code and the generated machine instructions (Optimize: Fast, O1)
void loop() {
while (1) {
digitalWriteFast(14, HIGH);
digitalWriteFast(14, LOW);
digitalWriteFast(14, HIGH);
digitalWriteFast(14, LOW);
digitalWriteFast(14, HIGH);
digitalWriteFast(14, LOW);
digitalWriteFast(14, HIGH);
digitalWriteFast(14, LOW);
}
}
00002fe8 <loop>:
2fe8: ldr r1, [pc, #20] ; (3000 <loop+0x18>)
2fea: movs r3, #2
2fec: ldr r2, [pc, #20] ; (3004 <loop+0x1c>)
2fee: str r3, [r1, #0]
2ff0: str r3, [r2, #0]
2ff2: str r3, [r1, #0]
2ff4: str r3, [r2, #0]
2ff6: str r3, [r1, #0]
2ff8: str r3, [r2, #0]
2ffa: str r3, [r1, #0]
2ffc: str r3, [r2, #0]
2ffe: b.n 2fee <loop+0x6>
3000: .word 0x400ff0c4
3004: .word 0x400ff0c8And here the same for the pin interface:
pin<14> Pin;
void loop() {
while (1) {
Pin = HIGH;
Pin = LOW;
Pin = HIGH;
Pin = LOW;
Pin = HIGH;
Pin = LOW;
Pin = HIGH;
Pin = LOW;
}
}
00002fe8 <loop>:
2fe8: ldr r3, [pc, #20] ; (3000 <loop+0x18>)
2fea: movs r1, #1
2fec: movs r2, #0
2fee: str r1, [r3, #0]
2ff0: str r2, [r3, #0]
2ff2: str r1, [r3, #0]
2ff4: str r2, [r3, #0]
2ff6: str r1, [r3, #0]
2ff8: str r2, [r3, #0]
2ffa: str r1, [r3, #0]
2ffc: str r2, [r3, #0]
2ffe: b.n 2fee <loop+0x6>
3000: .word 0x43fe1804Which should have the same performance