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[wpilib] Absolute Encoder API and behavior fixes (#4052)

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SetPositionOffset was added. Been requested multiple times, and easy to implement.

The javadocs mentioned GetPositionInRotation. It has tripped up many people how to get the absolute position from the encoder (You currently have to have precreated the DutyCycle object). Add this method (as GetAbsolutePostition) to make this easier to do.

The checks for making sure a matching set of values was read was doing direct double comparisions. This worked ok in the DutyCycle case, but has problems in the analog case. Solve this by using an epsilon comparison.

And finally, scale AnalogEncoders analog input to 0-1 instead of 0-5. This was reported a few years ago, but the issue was missed. This caused the encoder to count from 0-5, then 1-6, then 2-7 etc. This is solved and now works correctly.

Closes #3188
Closes #4046
Closes #4051

And fixes the following issue on CD
https://www.chiefdelphi.com/t/wpilib-analogencoder-java/372649
This commit is contained in:
Thad House
2022-02-24 22:45:15 -08:00
committed by GitHub
parent f88c435dd0
commit bc9e96e86f
6 changed files with 216 additions and 27 deletions
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26
wpilibc/src/main/native/cpp/AnalogEncoder.cpp
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@@ -10,6 +10,7 @@
#include "frc/AnalogInput.h"
#include "frc/Counter.h"
#include "frc/Errors.h"
#include "frc/RobotController.h"
using namespace frc;
@@ -42,6 +43,8 @@ void AnalogEncoder::Init() {
if (m_simDevice) {
m_simPosition = m_simDevice.CreateDouble("Position", false, 0.0);
m_simAbsolutePosition =
m_simDevice.CreateDouble("absPosition", hal::SimDevice::kInput, 0.0);
}
m_analogTrigger.SetLimitsVoltage(1.25, 3.75);
@@ -54,6 +57,11 @@ void AnalogEncoder::Init() {
m_analogInput->GetChannel());
}
static bool DoubleEquals(double a, double b) {
constexpr double epsilon = 0.00001;
return std::abs(a - b) < epsilon;
}
units::turn_t AnalogEncoder::Get() const {
if (m_simPosition) {
return units::turn_t{m_simPosition.Get()};
@@ -66,7 +74,8 @@ units::turn_t AnalogEncoder::Get() const {
auto pos = m_analogInput->GetVoltage();
auto counter2 = m_counter.Get();
auto pos2 = m_analogInput->GetVoltage();
if (counter == counter2 && pos == pos2) {
if (counter == counter2 && DoubleEquals(pos, pos2)) {
pos = pos / frc::RobotController::GetVoltage5V();
units::turn_t turns{counter + pos - m_positionOffset};
m_lastPosition = turns;
return turns;
@@ -80,10 +89,22 @@ units::turn_t AnalogEncoder::Get() const {
return m_lastPosition;
}
double AnalogEncoder::GetAbsolutePosition() const {
if (m_simAbsolutePosition) {
return m_simAbsolutePosition.Get();
}
return m_analogInput->GetVoltage() / frc::RobotController::GetVoltage5V();
}
double AnalogEncoder::GetPositionOffset() const {
return m_positionOffset;
}
void AnalogEncoder::SetPositionOffset(double offset) {
m_positionOffset = std::clamp(offset, 0.0, 1.0);
}
void AnalogEncoder::SetDistancePerRotation(double distancePerRotation) {
m_distancePerRotation = distancePerRotation;
}
@@ -98,7 +119,8 @@ double AnalogEncoder::GetDistance() const {
void AnalogEncoder::Reset() {
m_counter.Reset();
m_positionOffset = m_analogInput->GetVoltage();
m_positionOffset =
m_analogInput->GetVoltage() / frc::RobotController::GetVoltage5V();
}
int AnalogEncoder::GetChannel() const {