Massive Audio D2500.1 block series User Manual download pdf (Page 11)

was already used for the manual correction system, there was no other way to

display the percentage of pixels used without showing it on the projected screen,

which we had earlier eliminated considering it was only useful to power users.

The manual adjustment functionality relies on the user being able to select

the corner to be manipulated via a set of switches. While this binary representa-

tion would be natural to computer engineers and mathematicians, it would not

be self-explanatory to non-technical users. We were again constrained by the

labkit’s limited hardware input devices from making a more natural interface.

Of course, in theory we could have hooked up an external keyboard to another

one of the labkit’s ports, but this would have increased the complexity of our

project.

5 Module Descriptions

In this section, we give a more detailed description of each module, along with

the respective contributors.

5.1 par to ser (James)

This module converts a word of some size W (e.g. reg[W-1:0]) to a stream of

bits, one at each clock cycle, to be sent to the accelerometer. The higher-order

bits are produced ﬁrst. This module is necessitated by the SPI communication

protocol of the accelerometer.

5.2 ser to par (James)

This module converts a stream of bits received from the accelerometer, one per

clock cycle, to a word of desired width. It expects that the higher-order bits

will be received ﬁrst.

5.3 moving avg (James)

This module uses a ring buﬀer to store the last 32 acceleration readings received

from the accelerometer for a particular dimension. When a new sample is re-

ceived, the oldest sample is removed, the sum of the last 32 samples is adjusted

accordingly, and the average is recomputed. Since we compute the average over

32 (2

) samples, we do not need dividers and can use bit shifts for the needed

divisions. This module is meant to smooth acceleration readings, which are

expected to ﬂuctuate slightly even when the accelerometer is held ﬁxed.

5.4 acc (James)

The timing diagram for 4-wire SPI interaction with the accelerometer is shown

below:

1 2 ... 6 7 8 9 10 11 12 13 14 15 16 ... 244 245

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Massive Audio D2500.1 block series User Manual Page 11