Add Battery discharge example

Application_Specific/Battery_Test/Battery_Cycling/battery_discharge.tsp

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+--[[
+From Application Note: 
+Rechargeable Battery Charge/Discharge (Galvanic) Cycling Using 
+the Keithley Model 2450 or Model 2460 SourceMeter® SMU Instrument
+Link: https://www.tek.com/en/documents/application-note/rechargeable-battery-charge-and-discharge-galvanic-cycling-using-keithley
+
+Written By: Keithley Applications Engineering
+
+]]
+
+
+--This code discharges a 2500 mAH 1.2 V battery to 0.9 V with a
+--discharge current of 2.5A (1C).
+--Prior to executing code, reset instrument from front panel and
+--set the Output Off state of the Model 2460 to the High Z Mode
+--Insert USB drive to save readings
+
+--clear the buffer
+defbuffer1.clear()
+
+--Measurement Settings
+smu.measure.func = smu.FUNC_DC_CURRENT
+smu.measure.range = 2.5
+smu.measure.sense = smu.SENSE_4WIRE
+
+--Source Settings
+smu.source.func = smu.FUNC_DC_VOLTAGE
+smu.source.offmode = smu.OFFMODE_HIGHZ
+smu.source.level = 0.9
+smu.measure.terminals = smu.TERMINALS_REAR
+smu.source.range = 0.9
+smu.source.readback = smu.ON
+smu.source.ilimit.level = 2.5
+
+--Set the voltage limit for the battery to stop discharging
+--Set the variable for number of iterations
+voltLimit = 0.9001
+iteration = 1
+
+--Turn on the source output
+smu.source.output = smu.ON
+
+--Change display to user screen
+display.changescreen(display.SCREEN_USER_SWIPE)
+
+--Keep taking readings in the while loop until the measured voltage
+--is equal to the voltage limit
+while true do
+    --Take a reading and get the current, voltage and relative timestamp
+    curr = smu.measure.read(defbuffer1)
+    volt = defbuffer1.sourcevalues[iteration]
+    time = defbuffer1.relativetimestamps[iteration]
+    hours = time/3600
+
+    --Compare the measured voltage to the voltage limit
+    --Exit the loop if it is
+    if volt <= voltLimit then
+        break
+    end
+
+    --Print the # of completed cycles, the voltage and the time for
+    --the iteration. Display information on front panel
+    print("Completed Cycles: ",iteration, "Voltage: ", volt, "Time: ", time)
+    display.settext(display.TEXT1, string.format("Voltage = %.4fV", volt))
+    display.settext(display.TEXT2, string.format("Current = %.2fA, Time = %.2fHrs", curr, hours))
+
+    --Increment the number of iterations and wait 10 seconds
+    iteration = iteration + 1
+    delay(10)
+end
+
+--Turn the output off when the voltage limit is reached
+smu.source.output = smu.OFF
+
+FileNumber = file.open("/usb1/TestData.csv", file.MODE_WRITE)
+file.write(FileNumber,"Current,Voltage,Seconds\n")
+
+--Print out the measured values in a 4 column format
+print("nIteration:\tCurrent:\tVoltage:\tTime:\n")
+
+for i = 1, defbuffer1.n do
+    print(i, defbuffer1[i], defbuffer1.sourcevalues[i], defbuffer1.relativetimestamps[i])
+    file.write(FileNumber, string.format("%g,%g, %g\r\n",defbuffer1.readings[i], defbuffer1.
+    sourcevalues[i],defbuffer1.relativetimestamps[i]))
+end
+
+file.close(FileNumber)