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Lab 2 - Delay

Microcontrollers are extremely fast. A PIC that is clocked with an Xtal of 20MHz will execute about 5,000,000 assembly instructions, every second. To let the PIC communicate with ‘slow’ humans, we will need to slow it down at certain times. This is done by adding a Delay instruction.

EB006 Options	Setting	Jumper settings (EB006)	Jumper settings (HP488)
Power supply	External, 14V	J29: PSU	J29: PSU
PICmicro device	16F1937
Programming method	USB	J12,13,14: USB	J20: USB
Clocking method	XTAL	SW2: XTAL	S2: XTAL
R/C clock speed
Xtal frequency	19.660.800Hz
LVP Jumper selection	I/O Port	J11,16,17: I/O Port	J15,16,18: I/O
Port A E-block
Port B E-block	LED board
Port C E-block
Port D E-block
Port E E-block

Build > Project Options... > General Options	Build > Project Options... > Configure
Options Setting Clock speed 19 660 800 Hz Simulation speed As fast as possible	Options Setting Device 16F1937 RC/XT XTAL Watchdog timer Off

Output, Delay, Timing, binary code training, compiling a program to the PIC, clocking the PIC, PIC microcontroller basics.

LED’s, logic output levels, Multiprogrammer basics, speed of a microcontroller, time measurement with an oscilloscope.

Construct the system shown from E-blocks.

In the course navigate to the ‘Flowcode step-by-step’ and review the section on Basic Loops (step 4) and Decisions (step 7). In the course you will also find the sections on Clocking your PIC, and about PIC microcontroller basics useful. The descriptions of the multiprogrammer board and the led board are in the E-blocks section.

Also make use of the Help-function in Flowcode to get the info you need.

During these exercises you are going to send different 8-bit codes to port B of your Microcontroller. You'll learn how delays are used to slow the PIC down. Keep aware that your PIC microcontroller executes approximately at 5,000,000 assembly instructions per second and that the human eye in combination with the brain can only detect and understand approximately 3 stable images per second.

Letter	Meaning
L	Lab x
B	Basic complexity
I	Intermediate complexity
E	Expert complexity

L2-B1

Open the program [L1-B9] that you wrote in LAB 1 use 'Delay' instructions between the 20 different output instructions to visualise these different outputs, even at HS Xtal speeds. Download the program to the PIC that is clocked by the Xtal.

L2-B2

In the exercise above: start with a delay of 1 sec and make the delay shorter, step by step until the point that it gets too fast for your eyes to detect 2 different LED outputs. Do not test this in simulation mode. The timing in simulation mode is not always correct because it runs under a Windows operating system and this is not ‘real time’. Download the program to the PIC every time you change the delay and test it on the actual E-blocks.

L2-B3

Light LEDs 0-7 one by one, turn them all off and then back on. Use delays to make it all viewable on the actual E-blocks. Clocking of the PIC is done by an Xtal of 19,660,800Hz.

L2-I4

If you have an oscilloscope, use it to measure if the delays you have set up in Flowcode are correct. Make a detailed drawing of the oscilloscope image you see and add correct voltage and timing information to it. Make a note on it what delay-time you used in your Flowcode program.