backlash_comp.cpp

/*
*  backlash_comp.cpp
*  PHD Guiding
*
*  Created by Bruce Waddington
*  Copyright (c) 2015 Bruce Waddington and Andy Galasso
*  All rights reserved.
*
*  This source code is distributed under the following "BSD" license
*  Redistribution and use in source and binary forms, with or without
*  modification, are permitted provided that the following conditions are met:
*    Redistributions of source code must retain the above copyright notice,
*     this list of conditions and the following disclaimer.
*    Redistributions in binary form must reproduce the above copyright notice,
*     this list of conditions and the following disclaimer in the
*     documentation and/or other materials provided with the distribution.
*    Neither the name of Bret McKee, Dad Dog Development,
*     Craig Stark, Stark Labs nor the names of its
*     contributors may be used to endorse or promote products derived from
*     this software without specific prior written permission.
*
*  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
*  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
*  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
*  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
*  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
*  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
*  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
*  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
*  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
*  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
*  POSSIBILITY OF SUCH DAMAGE.
*
*/

#include "phd.h"
#include "backlash_comp.h"

static const unsigned int HISTORY_SIZE = 10;
static const unsigned int MAX_COMP_AMOUNT = 8000;             // max pulse in ms

BacklashComp::BacklashComp(Mount *theMount)
{
    m_pMount = theMount;
    m_pScope = reinterpret_cast<Scope *>(theMount);
    int lastAmt = pConfig->Profile.GetInt("/" + m_pMount->GetMountClassName() + "/DecBacklashPulse", 0);
    SetCompValues(lastAmt, false);
    if (m_pulseWidth > 0)
        m_compActive = pConfig->Profile.GetBoolean("/" + m_pMount->GetMountClassName() + "/BacklashCompEnabled", false);
    else
        m_compActive = false;
    m_justCompensated = false;
    m_lastDirection = NONE;
    if (m_compActive)
        Debug.Write(wxString::Format("BLC: Backlash compensation is enabled with correction = %d ms\n", m_pulseWidth));
    else
        Debug.Write("BLC: Backlash compensation is disabled\n");
}

int BacklashComp::GetBacklashPulseLimit()
{
    return MAX_COMP_AMOUNT;
}

// Private method to be sure all comp values are in-synch and don't exceed limits
// May change max-move value for Dec or ceiling depending on the context
void BacklashComp::SetCompValues(int requestedSize, bool autoAdjust)
{
    if (autoAdjust)
    {
        // Don't boost ceiling based on automatic adjustments
        m_pulseWidth = wxMax(0, wxMin(requestedSize, m_adjustmentCeiling));   // should have been done already
    }
    else
    {
        m_pulseWidth = wxMax(0, wxMin(requestedSize, MAX_COMP_AMOUNT));
        m_adjustmentCeiling = wxMin(2 * m_pulseWidth, MAX_COMP_AMOUNT);
    }
    if (m_pulseWidth > m_pScope->GetMaxDecDuration())
        m_pScope->SetMaxDecDuration(m_pulseWidth);
}

// Public method to ask for a particular backlash comp.  This method will adjust the ceiling to
// 2x the value
void BacklashComp::SetBacklashPulse(int ms)
{
    if (m_pulseWidth != ms)
    {
        SetCompValues(ms, false);
        pFrame->NotifyGuidingParam("Backlash comp amount", m_pulseWidth);
        Debug.Write(wxString::Format("BLC: Comp pulse set to %d ms\n", m_pulseWidth));
    }

    pConfig->Profile.SetInt("/" + m_pMount->GetMountClassName() + "/DecBacklashPulse", m_pulseWidth);
}

void BacklashComp::EnableBacklashComp(bool enable)
{
    if (m_compActive != enable)
    {
        pFrame->NotifyGuidingParam("Backlash comp enabled", enable);
    }

    m_compActive = enable;
    pConfig->Profile.SetBoolean("/" + m_pMount->GetMountClassName() + "/BacklashCompEnabled", m_compActive);
    Debug.Write(wxString::Format("BLC: Backlash comp %s, Comp pulse = %d ms\n", m_compActive ? "enabled" : "disabled", m_pulseWidth));
}

void BacklashComp::ResetBaseline()
{
    if (m_compActive)
    {
        m_lastDirection = NONE;
        m_justCompensated = false;
        Debug.Write("BLC: Last direction was reset\n");
    }
}

void BacklashComp::_TrackBLCResults(double yDistance, double minMove, double yRate)
{
    assert(m_justCompensated); // caller checks this

    // The previous Dec correction included a BLC

    // Record the history even if residual error is zero. Sign convention has nothing to do with N or S direction - only whether we
    // needed more correction (+) or less (-)
    GUIDE_DIRECTION dir = yDistance > 0.0 ? DOWN : UP;
    yDistance = fabs(yDistance);
    double miss;
    if (dir == m_lastDirection)
        miss = yDistance;            // + => we needed more of the same, under-shoot
    else
        miss = -yDistance;           // over-shoot
    minMove = fmax(minMove, 0);         // Algo w/ no min-move returns -1
    if (m_residualOffsets.GetCount() == HISTORY_SIZE)
    {
        m_residualOffsets.RemoveAt(0);
    }
    m_residualOffsets.Add(miss);

    if (yDistance >= minMove)           // Don't adjust for a residual error < min_move_equivalent
    {
        // Compute the average residual error
        int numPoints = m_residualOffsets.GetCount();
        double avgMiss = 0.;
        for (int inx = 0; inx < numPoints; inx++)
            avgMiss += m_residualOffsets.Item(inx);
        avgMiss = avgMiss / numPoints;

        if (abs(avgMiss) > minMove)                        // Don't make micro-adjustments
        {
            double corr = (int)floor(fabs(avgMiss / yRate) + 0.5);
            int nominalBLC;
            int newBLC;
            if (miss >= 0)                                  // We under-shot the target
            {
                if (avgMiss > 0)
                    nominalBLC = m_pulseWidth + corr;
                else
                    nominalBLC = m_pulseWidth;              // Need more evidence of under-shooting
                // Don't increase by more than 10% or go above ceiling
                newBLC = ROUND(fmin(m_pulseWidth * 1.1, wxMin(m_adjustmentCeiling, nominalBLC)));
            }
            else
            {                                              // we over-shot the target
                if (avgMiss < 0)
                    nominalBLC = m_pulseWidth - corr;
                else
                    nominalBLC = m_pulseWidth;            // Need more evidence of over-shooting
                // Don't decrease by more than 20% or go below zero
                newBLC = ROUND(fmax(0.8 * m_pulseWidth, wxMax(0, nominalBLC)));
            }

            if (newBLC != m_pulseWidth && numPoints > 2)
                m_residualOffsets.RemoveAt(0);               // Don't let initial big deflection dominate adjustments
            if (newBLC != m_pulseWidth)
            {
                Debug.Write(wxString::Format("BLC: Adjustment from %d to %d based on avg residual of %.1f px\n", m_pulseWidth, newBLC, avgMiss));
                pConfig->Profile.SetInt("/" + m_pMount->GetMountClassName() + "/DecBacklashPulse", newBLC);
                SetCompValues(newBLC, true);
            }

        }
    }

    m_justCompensated = false;
}

// Possibly add the backlash comp to the pending guide pulse (yAmount)
void BacklashComp::ApplyBacklashComp(int dir, double yDist, int *yAmount)
{
    m_justCompensated = false;

    if (!m_compActive || m_pulseWidth <= 0 || yDist == 0.0)
        return;

    if (m_lastDirection != NONE && dir != m_lastDirection)
    {
        *yAmount += m_pulseWidth;
        m_justCompensated = true;

        Debug.Write(wxString::Format("BLC: Dec direction reversal from %s to %s, backlash comp pulse of %d applied\n",
            m_lastDirection == NORTH ? "North" : "South", dir == NORTH ? "North" : "South", m_pulseWidth));
    }

    m_lastDirection = dir;
}

// Class for implementing the backlash graph dialog
class BacklashGraph : public wxDialog
{
    BacklashTool *m_BLT;
public:
    BacklashGraph(wxDialog *parent, BacklashTool *pBL);
    wxBitmap CreateGraph(int graphicWidth, int graphicHeight);
};

BacklashGraph::BacklashGraph(wxDialog *parent, BacklashTool *pBL)
    : wxDialog(parent, wxID_ANY, wxGetTranslation(_("Backlash Results")), wxDefaultPosition, wxSize(500, 400))
{
    m_BLT = pBL;

    // Just but a big button area for the graph with a button below it
    wxBoxSizer *vSizer = new wxBoxSizer(wxVERTICAL);
    // Use a bitmap button so we don't waste cycles in paint events
    wxBitmap theGraph = CreateGraph(450, 300);
    wxBitmapButton *graphButton = new wxBitmapButton(this, wxID_ANY, theGraph, wxDefaultPosition, wxSize(450, 300), wxBU_AUTODRAW | wxBU_EXACTFIT);
    vSizer->Add(graphButton, 0, wxALIGN_CENTER_HORIZONTAL | wxALL | wxFIXED_MINSIZE, 5);
    graphButton->SetBitmapDisabled(theGraph);
    graphButton->Enable(false);

    // ok button because we're modal
    vSizer->Add(
        CreateButtonSizer(wxOK),
        wxSizerFlags(0).Expand().Border(wxALL, 10));

    SetSizerAndFit(vSizer);
}

wxBitmap BacklashGraph::CreateGraph(int bmpWidth, int bmpHeight)
{
    wxMemoryDC dc;
    wxBitmap bmp(bmpWidth, bmpHeight, -1);
    wxColour decColor = pFrame->pGraphLog->GetDecOrDyColor();
    wxColour idealColor("WHITE");
    wxPen axisPen("GREY", 3, wxCROSS_HATCH);
    wxPen decPen(decColor, 3, wxSOLID);
    wxPen idealPen(idealColor, 3, wxSOLID);
    wxBrush decBrush(decColor, wxSOLID);
    wxBrush idealBrush(idealColor, wxSOLID);
    //double fakeNorthPoints[] =
    //{152.04, 164.77, 176.34, 188.5, 200.25, 212.36, 224.21, 236.89, 248.62, 260.25, 271.34, 283.54, 294.79, 307.56, 319.22, 330.87, 343.37, 355.75, 367.52, 379.7, 391.22, 403.89, 415.34, 427.09, 439.41, 450.36, 462.6};
    //double fakeSouthPoints[] =
    //{474.84, 474.9, 464.01, 451.83, 438.08, 426, 414.68, 401.15, 390.39, 377.22, 366.17, 353.45, 340.75, 328.31, 316.93, 304.55, 292.42, 280.45, 269.03, 255.02, 243.76, 231.53, 219.43, 207.35, 195.22, 183.06, 169.47};
    //std::vector <double> northSteps(fakeNorthPoints, fakeNorthPoints + 27);
    //std::vector <double> southSteps(fakeSouthPoints, fakeSouthPoints + 27);
    std::vector <double> northSteps = m_BLT->GetNorthSteps();
    std::vector <double> southSteps = m_BLT->GetSouthSteps();

    double xScaleFactor;
    double yScaleFactor;
    int xOrigin;
    int yOrigin;
    int ptRadius;
    int graphWindowWidth;
    int graphWindowHeight;
    int numNorth;
    double northInc;
    int numSouth;

    // Find the max excursion from the origin in order to scale the points to fit the bitmap
    double maxDec = -9999.0;
    double minDec = 9999.0;
    for (auto it = northSteps.begin(); it != northSteps.end(); ++it)
    {
        maxDec = wxMax(maxDec, *it);
        minDec = wxMin(minDec, *it);
    }

    for (auto it = southSteps.begin(); it != southSteps.end(); ++it)
    {
        maxDec = wxMax(maxDec, *it);
        minDec = wxMin(minDec, *it);
    }

    graphWindowWidth = bmpWidth;
    graphWindowHeight = 0.7 * bmpHeight;
    yScaleFactor = (graphWindowHeight) / (maxDec - minDec + 1);
    xScaleFactor = (graphWindowWidth) / (northSteps.size() + southSteps.size());

    // Since we get mount coordinates, north steps will always be in ascending order
    numNorth = northSteps.size();
    northInc = (northSteps.at(numNorth - 1) - northSteps.at(0)) / numNorth;
    numSouth = southSteps.size();       // Should be same as numNorth but be careful

    dc.SelectObject(bmp);
    dc.SetBackground(*wxBLACK_BRUSH);

    dc.SetFont(wxFont(12, wxFONTFAMILY_DEFAULT, wxFONTSTYLE_NORMAL, wxFONTWEIGHT_NORMAL));
    dc.Clear();

    // Bottom and top labels
    dc.SetTextForeground(idealColor);
    dc.DrawText(_("Ideal"), 0.7 * graphWindowWidth, bmpHeight - 25);
    dc.SetTextForeground(decColor);
    dc.DrawText(_("Measured"), 0.2 * graphWindowWidth, bmpHeight - 25);
    dc.DrawText(_("North"), 0.1 * graphWindowWidth, 10);
    dc.DrawText(_("South"), 0.8 * graphWindowWidth, 10);
    // Draw the axes
    dc.SetPen(axisPen);
    xOrigin = graphWindowWidth / 2;
    yOrigin = graphWindowHeight + 40;           // Leave room at the top for labels and such
    dc.DrawLine(0, yOrigin, graphWindowWidth, yOrigin);    // x
    dc.DrawLine(xOrigin, yOrigin, xOrigin, 0);             // y

    // Draw the north steps
    dc.SetPen(decPen);
    dc.SetBrush(decBrush);
    ptRadius = 2;

    for (int i = 0; i < numNorth; i++)
    {
        wxPoint where = wxPoint(i * xScaleFactor, round(yOrigin - (northSteps.at(i) - minDec) * yScaleFactor));
        dc.DrawCircle(wxPoint(i * xScaleFactor, round(yOrigin - (northSteps.at(i) - minDec) * yScaleFactor)), ptRadius);
    }

    // Draw the south steps
    for (int i = 0; i < numSouth; i++)
    {
        dc.DrawCircle(wxPoint((i + numNorth) * xScaleFactor, round(yOrigin - (southSteps.at(i) - minDec) * yScaleFactor)), ptRadius);
    }

    // Now show an ideal south recovery line
    dc.SetPen(idealPen);
    dc.SetBrush(idealBrush);

    double peakSouth = southSteps.at(0);
    for (int i = 1; i <= numNorth; i++)
    {
        wxPoint where = wxPoint((i + numNorth)* xScaleFactor, round(yOrigin - (peakSouth - i * northInc - minDec) * yScaleFactor));
        dc.DrawCircle(where, ptRadius);
    }

    dc.SelectObject(wxNullBitmap);
    return bmp;
}

// -------------------  BacklashTool Implementation
BacklashTool::BacklashTool()
{
    m_scope = TheScope();

    m_lastDecGuideRate = GetLastDecGuideRate();     // -1 if we aren't calibrated
    if (m_lastDecGuideRate > 0)
        m_bltState = BLT_STATE_INITIALIZE;
    else
    {
        m_bltState = BLT_STATE_ABORTED;
        m_lastStatus = _("Backlash measurement cannot be run - please re-run your mount calibration");
        Debug.Write("BLT: Could not get calibration data\n");
    }
    m_backlashResultPx = 0;
    m_backlashResultMs = 0;
    m_cumClearingDistance = 0;
    m_backlashExemption = false;
}

double BacklashTool::GetLastDecGuideRate()
{
    double rtnVal;
    Calibration lastCalibration;
    m_scope->GetLastCalibration(&lastCalibration);

    if (lastCalibration.isValid)
    {
        rtnVal = lastCalibration.yRate;
    }
    else
    {
        rtnVal = -1;
    }
    return rtnVal;
}

void BacklashTool::StartMeasurement()
{
    m_bltState = BLT_STATE_INITIALIZE;
    m_northBLSteps.clear();
    m_southBLSteps.clear();
    DecMeasurementStep(pFrame->pGuider->CurrentPosition());
}

void BacklashTool::StopMeasurement()
{
    m_bltState = BLT_STATE_ABORTED;
    DecMeasurementStep(pFrame->pGuider->CurrentPosition());
}

static bool OutOfRoom(const wxSize& frameSize, double camX, double camY, int margin)
{
    return camX < margin ||
        camY < margin ||
        camX >= frameSize.GetWidth() - margin ||
        camY >= frameSize.GetHeight() - margin;
}

void BacklashTool::DecMeasurementStep(const PHD_Point& currentCamLoc)
{
    double decDelta = 0.;
    double amt = 0;
    // double fakeDeltas []= {0, -5, -2, 2, 4, 5, 5, 5, 5 };
    PHD_Point currMountLocation;
    try
    {
        if (m_scope->TransformCameraCoordinatesToMountCoordinates(currentCamLoc, currMountLocation))
            throw ERROR_INFO("BLT: CamToMount xForm failed");
        if (m_bltState != BLT_STATE_INITIALIZE)
        {
            decDelta = currMountLocation.Y - m_markerPoint.Y;
            m_cumClearingDistance += decDelta;                                    // use signed value
            //if (m_bltState == BLT_STATE_CLEAR_NORTH)                            // DEBUG ONLY
            //    decDelta = fakeDeltas[wxMin(m_stepCount, 7)];
        }
        switch (m_bltState)
        {
        case BLT_STATE_INITIALIZE:
            m_stepCount = 0;
            m_markerPoint = currMountLocation;
            m_startingPoint = currMountLocation;
            // Compute pulse size for clearing backlash - just use the last known guide rate
            if (m_lastDecGuideRate <= 0)
                m_lastDecGuideRate = GetLastDecGuideRate();             // try it again, maybe the user has since calibrated
            if (m_lastDecGuideRate > 0)
            {
                m_pulseWidth = BACKLASH_EXPECTED_DISTANCE * 1.25 / m_lastDecGuideRate;      // px/px_per_ms, bump it to sidestep near misses
                m_acceptedMoves = 0;
                m_lastClearRslt = 0;
                m_cumClearingDistance = 0;
                m_backlashExemption = false;
                m_Rslt = MEASUREMENT_VALID;
                // Get this state machine in synch with the guider state machine - let it drive us, starting with backlash clearing step
                m_bltState = BLT_STATE_CLEAR_NORTH;
                m_scope->SetGuidingEnabled(true);
                pFrame->pGuider->EnableMeasurementMode(true);                   // Measurement results now come to us
            }
            else
            {
                m_bltState = BLT_STATE_ABORTED;
                m_lastStatus = _("Backlash measurement cannot be run - Dec guide rate not available");
                Debug.Write("BLT: Could not get calibration data\n");
            }
            break;

        case BLT_STATE_CLEAR_NORTH:
            // Want to see the mount moving north for 3 consecutive moves of >= expected distance pixels
            if (m_stepCount == 0)
            {
                // Get things moving with the first clearing pulse
                Debug.Write(wxString::Format("BLT starting North backlash clearing using pulse width of %d,"
                    " looking for moves >= %d px\n", m_pulseWidth, BACKLASH_EXPECTED_DISTANCE));
                pFrame->ScheduleCalibrationMove(m_scope, NORTH, m_pulseWidth);
                m_stepCount = 1;
                m_lastStatus = wxString::Format(_("Clearing North backlash, step %d"), m_stepCount);
                break;
            }
            if (fabs(decDelta) >= BACKLASH_EXPECTED_DISTANCE)
            {
                if (m_acceptedMoves == 0 || (m_lastClearRslt * decDelta) > 0)    // Just starting or still moving in same direction
                {
                    m_acceptedMoves++;
                    Debug.Write(wxString::Format("BLT accepted clearing move of %0.2f\n", decDelta));
                }
                else
                {
                    m_acceptedMoves = 0;            // Reset on a direction reversal
                    Debug.Write(wxString::Format("BLT rejected clearing move of %0.2f, direction reversal\n", decDelta));
                }
            }
            else
                Debug.Write(wxString::Format("BLT backlash clearing move of %0.2f px was not large enough\n", decDelta));
            if (m_acceptedMoves < BACKLASH_MIN_COUNT)                    // More work to do
            {
                if (m_stepCount < MAX_CLEARING_STEPS)
                {
                    if (fabs(m_cumClearingDistance) > BACKLASH_EXEMPTION_DISTANCE)
                    {
                        // We moved the mount a substantial distance north but the individual moves were too small - probably a bad calibration,
                        // so let the user proceed with backlash measurement before we push the star too far
                        Debug.Write(wxString::Format("BLT: Cum backlash of %0.2f px is at least half of expected, continue with backlash measurement\n", m_cumClearingDistance));
                        m_backlashExemption = true;
                    }
                    else
                    {
                        if (!OutOfRoom(pCamera->FullSize, currentCamLoc.X, currentCamLoc.Y, pFrame->pGuider->GetMaxMovePixels()))
                        {
                            pFrame->ScheduleCalibrationMove(m_scope, NORTH, m_pulseWidth);
                            m_stepCount++;
                            m_markerPoint = currMountLocation;
                            m_lastClearRslt = decDelta;
                            m_lastStatus = wxString::Format(_("Clearing North backlash, step %d (up to limit of %d)"), m_stepCount, MAX_CLEARING_STEPS);
                            Debug.Write(wxString::Format("BLT: %s, LastDecDelta = %0.2f px\n", m_lastStatus, decDelta));
                            break;
                        }
                    }
                }
                else
                {
                    m_lastStatus = _("Could not clear North backlash - test failed");
                    m_Rslt = MEASUREMENT_INVALID;
                    throw ERROR_INFO("BLT: Could not clear N backlash");
                }
            }
            if (m_acceptedMoves >= BACKLASH_MIN_COUNT || m_backlashExemption || OutOfRoom(pCamera->FullSize, currentCamLoc.X, currentCamLoc.Y, pFrame->pGuider->GetMaxMovePixels()))    // Ok to go ahead with actual backlash measurement
            {
                m_markerPoint = currMountLocation;            // Marker point at start of big Dec move North
                m_bltState = BLT_STATE_STEP_NORTH;
                double totalBacklashCleared = m_stepCount * m_pulseWidth;
                // Want to move the mount North at >=500 ms, regardless of image scale. But reduce pulse width if it would exceed 80% of the tracking rectangle -
                // need to leave some room for seeing deflections and dec drift
                m_pulseWidth = wxMax((int)NORTH_PULSE_SIZE, m_scope->GetCalibrationDuration());
                m_pulseWidth = wxMin(m_pulseWidth, (int)floor(0.7 * (double)pFrame->pGuider->GetMaxMovePixels() / m_lastDecGuideRate));
                m_stepCount = 0;
                // Move 50% more than the backlash we cleared or >=8 secs, whichever is greater.  We want to leave plenty of room
                // for giving South moves time to clear backlash and actually get moving
                m_northPulseCount = wxMax((MAX_NORTH_PULSES + m_pulseWidth - 1) / m_pulseWidth,
                                          totalBacklashCleared * 1.5 / m_pulseWidth);  // Up to 8 secs

                Debug.Write(wxString::Format("BLT: Starting North moves at Dec=%0.2f\n", currMountLocation.Y));
                // falling through to start moving North
            }

        case BLT_STATE_STEP_NORTH:
            if (m_stepCount < m_northPulseCount && !OutOfRoom(pCamera->FullSize, currentCamLoc.X, currentCamLoc.Y, pFrame->pGuider->GetMaxMovePixels()))
            {
                m_lastStatus = wxString::Format(_("Moving North for %d ms, step %d / %d"), m_pulseWidth, m_stepCount + 1, m_northPulseCount);
                Debug.Write(wxString::Format("BLT: %s, DecLoc = %0.2f\n", m_lastStatus, currMountLocation.Y));
                m_northBLSteps.push_back(currMountLocation.Y);
                pFrame->ScheduleCalibrationMove(m_scope, NORTH, m_pulseWidth);
                m_stepCount++;
                break;
            }
            else
            {
                // Either got finished or ran out of room
                Debug.Write(wxString::Format("BLT: North pulses ended at Dec location %0.2f, DecDelta=%0.2f px\n", currMountLocation.Y, decDelta));
                m_northBLSteps.push_back(currMountLocation.Y);
                if (m_stepCount < m_northPulseCount)
                {
                    if (m_stepCount < 0.5 * m_northPulseCount)
                    {
                        pFrame->Alert(_("Star too close to edge for accurate measurement of backlash. Choose a star farther from the edge."));
                        m_Rslt = MEASUREMENT_INVALID;
                    }
                    Debug.Write("BLT: North pulses truncated, too close to frame edge\n");
                }
                m_northRate = fabs(decDelta / (m_stepCount * m_pulseWidth));
                m_northPulseCount = m_stepCount;
                m_stepCount = 0;
                m_bltState = BLT_STATE_STEP_SOUTH;
                // falling through to moving back South
            }

        case BLT_STATE_STEP_SOUTH:
            if (m_stepCount < m_northPulseCount)
            {
                m_lastStatus = wxString::Format(_("Moving South for %d ms, step %d / %d"), m_pulseWidth, m_stepCount + 1, m_northPulseCount);
                Debug.Write(wxString::Format("BLT: %s, DecLoc = %0.2f\n", m_lastStatus, currMountLocation.Y));
                m_southBLSteps.push_back(currMountLocation.Y);
                pFrame->ScheduleCalibrationMove(m_scope, SOUTH, m_pulseWidth);
                m_stepCount++;
                break;
            }
            // Now see where we ended up - fall through to testing this correction
            Debug.Write(wxString::Format("BLT: South pulses ended at Dec location %0.2f\n", currMountLocation.Y));
            m_southBLSteps.push_back(currMountLocation.Y);
            m_endSouth = currMountLocation;
            m_bltState = BLT_STATE_TEST_CORRECTION;
            m_stepCount = 0;
            // fall through

        case BLT_STATE_TEST_CORRECTION:
            if (m_stepCount == 0)
            {
                // decDelta contains the nominal backlash amount
                m_backlashResultPx = fabs(decDelta);
                m_backlashResultMs = (int)(m_backlashResultPx / m_northRate);          // our north rate is probably better than the calibration rate
                if (m_Rslt == MEASUREMENT_VALID)
                {
                    if (m_backlashResultMs >= 0.8 * m_northPulseCount * m_pulseWidth)
                        m_Rslt = MEASUREMENT_IMPAIRED;      // May not have moved far enough north for accurate measurement
                }
                Debug.Write(wxString::Format("BLT: Backlash amount is %0.2f px, %d ms\n", m_backlashResultPx, m_backlashResultMs));
                // Don't try this refinement if the clearing pulse will cause us to lose the star
                if (m_backlashResultPx < pFrame->pGuider->GetMaxMovePixels())
                {
                    m_lastStatus = wxString::Format(_("Issuing test backlash correction of %d ms"), m_backlashResultMs);
                    Debug.Write(m_lastStatus + "\n");
                    // This should put us back roughly to where we issued the big North pulse unless the backlash is very large
                    pFrame->ScheduleCalibrationMove(m_scope, SOUTH, m_backlashResultMs);
                    m_stepCount++;
                }
                else
                {
                    int maxFrameMove = (int)floor((double)pFrame->pGuider->GetMaxMovePixels() / m_northRate);
                    Debug.Write(wxString::Format("BLT: Clearing pulse is very large, issuing max S move of %d\n", maxFrameMove));
                    pFrame->ScheduleCalibrationMove(m_scope, SOUTH, maxFrameMove);       // One more pulse to cycle the state machine
                    m_bltState = BLT_STATE_RESTORE;
                }
                break;
            }
            // See how close we came, maybe fine-tune a bit
            Debug.Write(wxString::Format("BLT: Trial backlash pulse resulted in net DecDelta = %0.2f px, Dec Location %0.2f\n", decDelta, currMountLocation.Y));
            if (fabs(decDelta) > TRIAL_TOLERANCE)
            {
                double pulse_delta = fabs(currMountLocation.Y - m_endSouth.Y);
                if ((m_endSouth.Y - m_markerPoint.Y) * decDelta < 0)                // Sign change, went too far
                {
                    m_backlashResultMs *= m_backlashResultPx / pulse_delta;
                    Debug.Write(wxString::Format("BLT: Trial backlash resulted in overshoot - adjusting pulse size by %0.2f\n", m_backlashResultPx / pulse_delta));
                }
                else
                {
                    double corr_factor = (m_backlashResultPx / pulse_delta - 1.0) * 0.5 + 1.0;          // apply 50% of the correction to avoid over-shoot
                    //m_backlashResultMs *= corr_factor;
                    Debug.Write(wxString::Format("BLT: Trial backlash resulted in under-correction - under-shot by %0.2f\n", corr_factor));
                }
            }
            else
                Debug.Write("BLT: Initial backlash pulse resulted in final delta of < 2 px\n");

            m_bltState = BLT_STATE_RESTORE;
            m_stepCount = 0;
            // fall through

        case BLT_STATE_RESTORE:
            // We could be a considerable distance from where we started, so get back close to the starting point without losing the star
            if (m_stepCount == 0)
            {
                Debug.Write(wxString::Format("BLT: Starting Dec position at %0.2f, Ending Dec position at %0.2f\n", m_markerPoint.Y, currMountLocation.Y));
                amt = fabs(currMountLocation.Y - m_startingPoint.Y);
                if (amt > pFrame->pGuider->GetMaxMovePixels())
                {
                    m_restoreCount = (int)floor((amt / m_northRate) / m_pulseWidth);
                    Debug.Write(wxString::Format("BLT: Final restore distance is %0.1f px, approx %d steps\n", amt, m_restoreCount));
                    m_stepCount = 0;
                }
                else
                    m_bltState = BLT_STATE_WRAPUP;
            }
            if (m_stepCount < m_restoreCount)
            {

                pFrame->ScheduleCalibrationMove(m_scope, SOUTH, m_pulseWidth);
                m_stepCount++;
                m_lastStatus = _("Restoring star position");
                Debug.Write(wxString::Format("BLT: Issuing restore pulse count %d of %d ms\n", m_stepCount, m_pulseWidth));
                break;
            }
            m_bltState = BLT_STATE_WRAPUP;
            // fall through

        case BLT_STATE_WRAPUP:
            m_lastStatus = _("Measurement complete");
            CleanUp();
            m_bltState = BLT_STATE_COMPLETED;
            break;

        case BLT_STATE_COMPLETED:
            break;

        case BLT_STATE_ABORTED:
            m_lastStatus = _("Measurement halted");
            Debug.Write("BLT: measurement process halted by user or by error\n");
            CleanUp();
            break;
        }                       // end of switch on state
    }
    catch (const wxString& msg)
    {
        Debug.Write(wxString::Format("BLT: Exception thrown in logical state %d\n", (int)m_bltState));
        m_bltState = BLT_STATE_ABORTED;
        m_lastStatus = wxString::Format(_("Measurement encountered an error: %s"), msg);
        Debug.Write("BLT: " + m_lastStatus + "\n");
        CleanUp();
    }
}

// Launch modal dialog to show the BLT graph
void BacklashTool::ShowGraph(wxDialog *pGA)
{
    BacklashGraph dlg(pGA, this);
    dlg.ShowModal();
}

void BacklashTool::CleanUp()
{
    m_scope->GetBacklashComp()->ResetBaseline();        // Normal guiding will start, don't want old BC state applied
    pFrame->pGuider->EnableMeasurementMode(false);
}

//------------------------------  End of BacklashTool implementation