2. If you have not already viewed the oscilloscope video with an
oscilloscope at hand, do it now.
3. Perform a scope checkout (what you did in Step 13 of Lab 2).
4. All measurements will be made using pins on header JP1 (labelled
both “JP1” and “GPIO 0”) of the DE2 board, as shown in Figure
3.20. In most cases, you will see that these headers are covered
with a daughterboard that passes all of the header pins to the top
side, but also reroutes many pins to test points and other headers
that will be used later (Figure 3.21, top). Locate the JP1 header
now, and examine Table C.4 (in Appendix C), which shows the
assignments of signals to those pins. Note that the pins 12 and 30
on both GPIO headers are grounded. (The numbering of the pins
is also shown in Figure 3.20. This is standard numbering for dualrow headers, and is not the same counter-clockwise numbering
that is used for DIPs.) The oscilloscope probe ground must be
connected to DE2 ground, but it is extremely difficult to connect
the “alligator clip” of the probe ground to those header pins
without a risk of shorting something. For that reason, ground is
also available at several labelled test points on the daughterboard,
which are color-coded as black.
TURN THE DE2 BOARD OFF. Depending on the current setup of
the lab, connect the ground of BOTH probes to either
• ground test points on the daughterboard (preferred, and
shown in Figure 3.21, top), or
• extension leads with a single female receptacle that can be
attached to pins 12 or 30 (Figure 3.21, bottom).
5. The probes themselves must be connected to signals of interest.
The spring-loaded signal probe “grabber” tips will not reliably
grasp pins inside the header, nor the equivalent pins that emerge
from the top of the daughterboard. The test point labelled “TP2”
is directly connected to pin 2 on header JP1, which is the location
of the first signal that we wish to measure. Connect the probe for
Channel 1 of the oscilloscope to TP1. If there is no daughterboard,
use special leads or adapters provided to connect to JP1-2. From
Table C.4, you can see that pin JP1-2 is a direct connection to a
pin on the FPGA. This will be the output of a circuit that you will
Lab 3
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Figure 3.21. Two examples of connecting a probe to JP1, pin 2. In both cases, the
probe ground is connected to DE2 ground. Top: The normal setup provides a
daughterboard with convenient signal and ground test points. Bottom: In the absence
of the daughterboard, this setup uses a two-row plug to extend most of the first 16
pins to a higher point, clear of the shroud.
soon download to the DE2 board, without knowing exactly what
that circuit is. This output will be called Vout. Power up the DE2
board.
6. Determine if your DE2 board has an EP2C35 chip (a “regular”
DE2) or an EP2C70 chip (a DE2-70) by looking at the printed
information on the chip itself. Then choose the correct compiled
circuit:
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