Use timer interrupt functions to measure reaction times. More...

Functions
def	Lab0x02_B.OCInterrupt (tim2)
	Callback function for the OC Interrupt. More...

def	Lab0x02_B.ICInterrupt (tim2)
	Callback function for the IC Interrupt. More...

Variables
	Lab0x02_B.pinPB3 = pyb.Pin (pyb.Pin.cpu.B3)
	Pin hardwired to the B1 USER button. More...

	Lab0x02_B.pinA5 = pyb.Pin (pyb.Pin.board.PA5, mode = pyb.Pin.OUT_PP)
	Pin attribute for LED. More...

	Lab0x02_B.tim2 = pyb.Timer(2, period = 0x7fffffff, prescaler = 79)
	32-bit timer used to control the IC and OC interrupts. More...

	Lab0x02_B.t2ch1 = tim2.channel(1, pyb.Timer.OC_TOGGLE, pin=pinA5, polarity=tim2.HIGH, callback=OCInterrupt)
	Channel 1 attribute for pyb timer for OC interrupt. More...

	Lab0x02_B.t2ch2 = tim2.channel(2, pyb.Timer.IC, pin=pinPB3, polarity=tim2.FALLING, callback=ICInterrupt)
	Channel 2 attribute for pyb timer for IC interrupt. More...

int	Lab0x02_B.S0_M_WAITING = 0
	Mainscript state 0 to wait for button to be pressed.

int	Lab0x02_B.S1_M_CALCULATE = 1
	Mainscript state 1 to calculate the reaction time.

bool	Lab0x02_B.buttonPress = False
	Variable to keep track if the button is pressed or not.

list	Lab0x02_B.rxnTimes = []
	List to hold the reaction times (later will be averaged)

int	Lab0x02_B.avgRxnTime = 0
	Variable to display the average of the reaction times.

int	Lab0x02_B.buttonPressCount = 0
	Variable to determine the count at which the button was pressed.

int	Lab0x02_B.lastCompareVal = 0
	lastCompareVal holds the previous compare value for OC More...

int	Lab0x02_B.newCompareVal = lastCompareVal + random.randrange(2000000,3000000)
	newCompareVal holds the future time to trigger the OC More...

int	Lab0x02_B.stateOC = 0
	Mini finite state machine within the OC interrupt.

int	Lab0x02_B.stateM = 0
	Main state machine state variable for mini FSM.

bool	Lab0x02_B.calculate = True
	Should the program calculate a reaction time?

int	Lab0x02_B.thisRxnTime = buttonPressCount - lastCompareVal
	The current reaction time for the run. More...

Detailed Description

Use timer interrupt functions to measure reaction times.

Using the Nucleo L476RG board, two timers will be configured in an Output Compare (OC) and Input Capture (IC) mode in order to measure the reaction time of a user pressing the B1 button when the LD2 LED turns on. The LED will be controlled with the OC timer, where it will be off for a random value between 2-3 seconds, turn on for exactly 1 second, and repear. The IC timer will be triggered when the B1 button is pressed on a falling edge. The difference in these two regions will be used to calculate a reaction time.
See source code here: https://bitbucket.org/ryanmclaug/matt_ryan_shared/src/master/405_Lab0x02/Lab0x02_B.py

Figure 1. Overall program FSM.

Figure 2. FSM Output Compare Interrupt.

Author: Ryan McLaughlin; Matthew Frost

Date: Originally created on 04/26/21
Last modified on 04/27/21

Function Documentation

◆ ICInterrupt()

def Lab0x02_B.ICInterrupt ( tim2 )

Callback function for the IC Interrupt.

The B1 button is hardwired to pin PB3, which is controlled by Timer 2, Channel 2. This is configured as an IC timer, with a polarity on the falling edge. When the button is pressed, the timerchannel.capture() feature is used to get the current count of the system.

◆ OCInterrupt()

def Lab0x02_B.OCInterrupt ( tim2 )

Callback function for the OC Interrupt.

Timer 2, Channel 1 is configured in an output compare method for timing the LED. The channel is configured with the OC_TOGGLE mode, where the pin for the LED is toggled on and off to control the light emitted. Within this callback, the compare value is reset to account for the next callback. This alternates between staying off for 2-3 seconds and staying on for exactly 1 second.

Variable Documentation

◆ lastCompareVal

int Lab0x02_B.lastCompareVal = 0

lastCompareVal holds the previous compare value for OC

The lastCompareVal is essentially the 'start' to the new LEd control. If the LED is initially off, the lastCompareVal stores the time that the LED switched from on to off. If the LED is on, lastCompareVal stores the count at which the LED turned on.

◆ newCompareVal

int Lab0x02_B.newCompareVal = lastCompareVal + random.randrange(2000000,3000000)

newCompareVal holds the future time to trigger the OC

The newCompareVal holds the count at which the OC interrupt will be triggered again. So, this value stores either the random 2-3 seconds where the LED is off, or the exact 1 second where the LED is on for.

◆ pinA5

Lab0x02_B.pinA5 = pyb.Pin (pyb.Pin.board.PA5, mode = pyb.Pin.OUT_PP)

Pin attribute for LED.

The A5 pin will be used to control the OC interrupt callback for the LED.

◆ pinPB3

Lab0x02_B.pinPB3 = pyb.Pin (pyb.Pin.cpu.B3)

Pin hardwired to the B1 USER button.

The PB3 pin will be used in order to control the IC interrupt from an external press of the B1 USER button on the Nucleo.

◆ t2ch1

Lab0x02_B.t2ch1 = tim2.channel(1, pyb.Timer.OC_TOGGLE, pin=pinA5, polarity=tim2.HIGH, callback=OCInterrupt)

Channel 1 attribute for pyb timer for OC interrupt.

Channel 1 of Timer 2 will be used for the OC control. The polarity of the A5 pin will be set to high.

◆ t2ch2

Lab0x02_B.t2ch2 = tim2.channel(2, pyb.Timer.IC, pin=pinPB3, polarity=tim2.FALLING, callback=ICInterrupt)

Channel 2 attribute for pyb timer for IC interrupt.

Channel 2 of Timer 2 will be used for the IC control. The polarity of the PB3 will be set to a falling edge (the equivalent of the button being pressed instead of released).

◆ thisRxnTime

int Lab0x02_B.thisRxnTime = buttonPressCount - lastCompareVal

The current reaction time for the run.

Calculate the reaction time in microseconds, which is convenient since the prescaler made the count equal to 1 microsecond.

◆ tim2

Lab0x02_B.tim2 = pyb.Timer(2, period = 0x7fffffff, prescaler = 79)

32-bit timer used to control the IC and OC interrupts.

Timer 2 will be used for its 32-bit counter for high definition with a period of 0x7FFFFFF and prescaler = 79. By using those period and prescaler values, the timer will take over 35 minutes before overflow (thus virtually eliminating any overflow errors). The prescaler, with a frequency of 80 MHz, will allow for a count to equal 1 microsecond, a convenient measurement.

Functions

Variables