diff --git a/Packages/MIES/MIES_SweepFormula_PSX.ipf b/Packages/MIES/MIES_SweepFormula_PSX.ipf
index 1fe32562be..85fa946c5a 100644
--- a/Packages/MIES/MIES_SweepFormula_PSX.ipf
+++ b/Packages/MIES/MIES_SweepFormula_PSX.ipf
@@ -1128,9 +1128,8 @@ static Function [WAVE/D results, WAVE eventIndex, WAVE marker, WAVE/T comboKeys]
 		case "amp":
 			propLabel = "amplitude"
 			break
-		case "xpos":
-			propLabel = "onset_t"
-			break
+		// add peak, peak_t, deconvPeak, deconvPeak_t, baseline_t, baseline
+		// add slew rate and slew rate time
 		case "xinterval":
 			propLabel = "iei"
 			break
@@ -1146,6 +1145,7 @@ static Function [WAVE/D results, WAVE eventIndex, WAVE marker, WAVE/T comboKeys]
 		case "fitresult":
 			propLabel = "Fit result"
 			break
+			// add onset time
 		case "risetime":
 			propLabel = "Rise Time"
 			break
@@ -1937,12 +1937,16 @@ static Function PSX_UpdateOffsetInAllEventGraph(string win)
 			switch(offsetMode)
 				case PSX_HORIZ_OFFSET_ONSET:
 					xOffset = 0
-					yOffset = sweepDataOffFilt(psxEvent[i][%onset_t])
+					yOffset = sweepDataOffFilt(psxEvent[i][%$"Onset Time"])
 					break
 				case PSX_HORIZ_OFFSET_PEAK:
-					xOffset = first - psxEvent[i][%onset_t]
+					xOffset = first - psxEvent[i][%peak_t]
 					yOffset = 0
 					break
+//				case PSX_HORIZ_OFFSET_SLEW: // call it Slew Rate
+//					xOffset = first - psxEvent[i][%$"Slew Rate Time"]
+//					yOffset = 0
+//					break
 				default:
 					ASSERT(0, "Invalid offset mode")
 			endswitch
@@ -2740,7 +2744,7 @@ static Function PSX_UpdateSingleEventTextbox(string win, [variable eventIndex])
 
 	Make/FREE/T/N=(8, 2) input
 
-	input[0][0] = {"Event State:", "Fit State:", "Fit Result:", "Event:", "Onset:", "IeI:", "Amp (rel.):", "Tau:", "Rise time:"}
+	input[0][0] = {"Event State:", "Fit State:", "Fit Result:", "Event:", "Deconv Peak:", "IeI:", "Amp (rel.):", "Tau:", "Rise time:"}
 	input[0][1] = {PSX_StateToString(psxEvent[eventIndex][%$"Event manual QC call"]),        \
 	               PSX_StateToString(psxEvent[eventIndex][%$"Fit manual QC call"]),          \
 	               PSX_FitResultToString(psxEvent[eventIndex][%$"Fit Result"]),              \
@@ -2750,6 +2754,7 @@ static Function PSX_UpdateSingleEventTextbox(string win, [variable eventIndex])
 	               num2str(psxEvent[eventIndex][%amplitude], "%8.02f") + " [" + yUnit + "]", \
 	               num2str(psxEvent[eventIndex][%tau], "%8.02f") + " [ms]",                  \
 	               num2str(psxEvent[eventIndex][%$"Rise Time"], "%8.02f") + " [ms]"}
+					  // TODO add onset time before rise time
 
 	str = "\F'Consolas'" + FormatTextWaveForLegend(input)
 
@@ -4698,6 +4703,7 @@ Function/WAVE PSX_OperationStats(variable jsonId, string jsonPath, string graph)
 	WAVE/Z    selectData = selectDataComp[%SELECTION]
 	WAVE/WAVE range      = selectDataComp[%RANGE]
 
+	// TODO add onsetTime and slew rate, slew 
 	Make/FREE/T allProps = {"amp", "xpos", "xinterval", "tau", "estate", "fstate", "fitresult", "risetime"}
 	prop = SFH_GetArgumentAsText(jsonID, jsonPath, graph, SF_OP_PSX_STATS, 2, allowedValues = allProps)
 	Make/FREE/T allStates = {"accept", "reject", "undetermined", "all", "every"}
diff --git a/Packages/MIES/MIES_WaveDataFolderGetters.ipf b/Packages/MIES/MIES_WaveDataFolderGetters.ipf
index bd8d87c89b..499de49684 100644
--- a/Packages/MIES/MIES_WaveDataFolderGetters.ipf
+++ b/Packages/MIES/MIES_WaveDataFolderGetters.ipf
@@ -8212,6 +8212,64 @@ Function UpgradePSXEventWave(WAVE psxEvent)
 	endif
 End
 
++static Function/WAVE PSX_CalculateOnsetTimeImpl(WAVE psxEvent, WAVE sweepData, variable kernelAmp, variable diffThreshPerc)
++
++    variable numEvents
++
++    Make/FREE/D/N=0 diff
++    Differentiate/EP=1 sweepData/D=diff
++
++    numEvents = DimSize(psxEvent, ROWS)
++    Make/FREE/D/N=(numEvents) onset
++
++    Multithread onset[] = PSX_CalculateOnsetTimeImplEvent(diff, psxEvent[p][%peak_t], psxEvent[p][%baseline_t], kernelAmp, diffThreshPerc)
++
++    return onset
++End
++
++threadsafe static Function PSX_CalculateOnsetTimeImplEvent(WAVE diff, variable peak_t, variable baseline_t, variable kernelAmp, variable diffThreshPerc)
++
++    variable diffPeak, diffPeak_t, level
++
++    ASSERT_TS(peak_t < baseline_t, "Unexpected ordering of peak_t and baseline_t")
++
++    WaveStats/Q/M=1/R=(peak_t, baseline_t) diff
++    if(kernelAmp > 0)
++        diffPeak   = V_max
++        diffPeak_t = V_maxLoc
++    elseif(kernelAmp < 0)
++        diffPeak   = V_min
++        diffPeak_t = V_minLoc
++    else
++        ASSERT_TS(0, "Unsupported case: kernelAmp being zero")
++    endif
++   // TODO store diffPeak, diffPeak_t in psxEvent
++   // Names: "Slew Rate" and "Slew Rate Time"
++
++    // TODO check sign
++    level = diffThreshPerc * (diffPeak - diff(baseline_t)) 
++    
++    // search backwards in time
++    FindLevel/R=(diffPeak_t, baseline_t) diff, level
++
++    if(V_flag)
+        return NaN
+     endif
+     
+     return V_levelX
++End
++
++// New function:
++//  PSX_OnsetTime(peak_t, baseline_t, DiffV)
++/// onset_t =  time of the percentDiffThresh amplitude of the 1st differential of the event
++/// percentDiffThresh taken from psxRiseTime user input, default to 5%
++// Order of operations:
++// 1.   DiffV = Differentiated sweep trace
++// 2.   DiffPeak =  the peak of the differentiated trace between [peak_t - baseline_t], peak = min for (–) kernel sign, max for (+) kernel sign
++// 3.   DiffPeak_t = time of DiffPeak
++// 4.   onset_t = findlevel/R= (DiffPeak_t, baseline_t) wave = DiffV, level=(percentDiffThresh * DiffPeak)
++// 5.   Return onset_t
++
 /// @brief Return a 2D events wave as free wave
 ///
 /// Rows: