Encoder Example With MKR Vidor 4000

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1/*
2
3   This sketch shows how to use the Encoder IP in MKRVidor 4000
4
5   Quadrature encoders are a very common way to detect position (and speed) of a moving part, like a DC motor.
6
7   Normally, in the microcontroller world, decoding a quadrature encoder has serious limitations since all edges must be counted, otherwise the final number will be wrong. This is usually accomplished using interrupts, but over a certain revolution speed the intinsic overhead of servicing an interrupt destroys the count reliability.
8
9   Using the FPGA to perform decoding allows:
10
11    - not to lose any edge until the revolution speed is less than some million RPM :)
12
13    - we can "read" the encoder at any time, because the FPGA is counting independently
14
15    Circuit:
16
17      connect ENC_A to A0 and ENC_B to A1
18
19*/
20
21#include "VidorGraphics.h"
22#include "VidorEncoder.h"
23
24// Initialize Encoder #0 (connected to A0 and A1)
25// Refer to the online documentation to find which pins correspond to a given index
26// This assignment may change between bitstreams
27
28VidorEncoder encoder(0);
29
30void setup() {
31
32  Serial.begin(9600);
33
34  // wait for the serial monitor to open,
35
36  // if you are powering the board from a USB charger remove the next line
37
38  while (!Serial);
39
40  // Let's start the FPGA
41
42  if (!FPGA.begin()) {
43
44    Serial.println("Initialization failed!");
45
46    while (1) {}
47
48  }
49}
50
51void loop() {
52
53  // Read the encoder
54
55  int value = encoder.read();
56
57  Serial.print("Encoder value: ");
58
59  Serial.println(value);
60
61#if 1
62
63  // Wait one second with interrupts disabled
64
65  noInterrupts();
66
67  // We can't call delay() since it uses interrupts, so use busy loops
68
69  for (int i = 0; i < F_CPU / 10; i++) {
70
71    asm ("nop");
72
73  }
74
75  interrupts();
76
77#else
78
79  delay(200);
80#endif
81
82  if (value >= 200 || value <= -200) {
83
84    // Reset the count
85
86    encoder.write(0);
87
88  }
89}