commit 8c27b8db3c4c6123fc51c575f728b5350fd69ff2
parent 439d9319f80b2728437579dcaa69b445d98c539b
Author: Martin Kloeckner <mjkloeckner@gmail.com>
Date: Sun, 3 Dec 2023 17:22:20 -0300
Time difference of using Port Manipulation and Builtin Functions
Diffstat:
| M | README.md | | | 38 | +++++++++++++++++++++++++++++++++----- |
1 file changed, 33 insertions(+), 5 deletions(-)
diff --git a/README.md b/README.md
@@ -1,13 +1,41 @@
# Arduino DAC Multiport
-This is an Arduino program to make a 6Bit DAC using an [R2R
+This is an Arduino program to make a 6 bit DAC using an [R2R
ladder](https://en.wikipedia.org/wiki/Resistor_ladder) connected to the
-corresponding pins.
+corresponding pins on the Arduino.
-The code is a slight modified version of a previously existing one that adds the
-ability to use pins from different ports instead of all the pins from the same
-port.
+The code is a slight modified version of a previously existing one provided by
+[FIUBA](https://es.wikipedia.org/wiki/Facultad_de_Ingenier%C3%ADa_(Universidad_de_Buenos_Aires))'s
+lecturers from course "Introducción a la Ingeniería Electrónica", and
+corresponds to the Final Group Project. The modification adds the ability to use
+pins from different ports instead of all the pins from the same port.
The ports are 8 bits registers that Arduino uses to internally represents the
output pins. You can find which pin correspond to which port by looking on any
Arduino pinout diagram, being the most common ports PORTB, PORTC and PORTD.
+
+The code uses PORT manipulation since its faster than using builtin function
+like pinMode(), and thus improving the softness of the recreated wave by the
+R2R.
+
+The following statements produce the same effect on the arduino output pins and
+shows the difference in speed of using builtin functions and port manipulation
+(Taken from [this arduino forum
+question](https://forum.arduino.cc/t/ddr-vs-pinmode-solved/497927/3))
+
+```c
+pinMode(5, OUTPUT); takes 71 clock cycles (~4.43us@16Mhz)
+DDRD |= 0b00010000; takes 2 clock cycles (~0.125us@16Mhz)
+bitSet(PORTD, 5, 1); takes 2 clock cycles (~0.125us@16Mhz)
+```
+
+Also assigning the new value to the port allow for multiple ports to be updated
+on a single statement, for example turning on both pin 4 and 5 at the same time
+can be done with the following statement
+
+```c
+DDRD |= 0b00011000;
+```
+
+For more information I suggest reading [Arduino Reference on Port
+Manipulation](https://www.arduino.cc/en/Reference/PortManipulation)
