1. Introduction
2. Concept of Project and Motivations
3. Interface and Interaction Design
 3.1 Additional Controls
 3.2 Housing
 3.3 Circuitry and Interfacing
4. Uses
5. Breakdown of Timeline
6. Resources

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3.3 Circuitry and Interfacing:  

The Super Retro Fader Box is designed to interface with a computer via the PIC 18F4550 microcontroller made by Microchip. The block diagram in figure 4 shows how the interface connects with a computer. The unit has two types of interaction, faders and buttons. Faders are continuous controllers that require an analog to digital conversion in order to be understood by the computer. Whereas buttons map well to digital, therefore requiring no conversion. Because of the number of inputs from the mixer two PIC’s are required in order to map all of the controls to the computer.

Each of the PIC 18F4550 microcontrollers has thirteen analog inputs (that have A to D conversion built in) and seventeen digital inputs. But the Super Retro Fader Box has 24 faders and pushbuttons. It would be possible to design a system that used multiplexors to get all of the controls interfaced to one PIC, but a simpler solution is to divide the Super Retro Faderbox into two groups, with each group is assigned to its own PIC.

 

Figure 4. Block diagram the Super Retro Fader Box.

By dividing the Super Retro Faderbox into a top group that consists of the upper bank of faders and buttons and the crossfader on the right of the board, and a bottom group that consists of the bottom bank of faders and buttons and the left crossfader, each group will have the exact same number of controls to map to the PIC. Details for the mappings from one of the group’s controls to the pins on a 18F4550 PIC are found in Table 1.

Figure 5 shows the schematic for one of the groups of the Super Retro Faderbox. The schematic is a simple extension of the “CREATE Hello World” circuit (http://www.create.ucsb.edu/~dano/CUI/) developed by Dan Overholt. The main additions are the inclusion of the slider and pushbutton schematics. The sliders are wired like most potentiometers, in a voltage divider scheme. The pushbuttons control not only the digital input to the microcontroller, but turn on an LED as well. As stated above, the LED is used to tell the user the current state of the button (on or off).

Port
Function
Application

RA0

Analog input 0

Fader 1

RA1

Analog input 1

Fader 2

RA2

Analog input 2

Fader 3

RA3

Analog input 3

Fader 4

RA4

Digital I/O

Pushbutton 9

RA5

Analog input 4

Fader 5

RB0

Analog input12

Mixer 13 (crossfade)

RB1

Analog input10

Fader 11

RB2

Analog input 8

Fader 9

RB3

Analog input 9

Fader 10

RB4

Analog input11

Fader 12

RB5

Digital I/O

USED FOR PROG

RB6

Digital I/O

USED FOR PROG

RB7

Digital I/O

USED FOR PROG

RC0

Digital I/O

Pushbutton 10

Port
Function
Application

RC1

Digital I/O or PWM

NOT USED

RC2

Digital I/O or PWM

NOT USED

RC6

Digital I/O

Pushbutton 11

RC7

Digital I/O

Pushbutton 12

RD0

Digital I/O

Pushbutton 1

RD1

Digital I/O

Pushbutton 2

RD2

Digital I/O

Pushbutton 3

RD3

Digital I/O

Pushbutton 4

RD4

Digital I/O

Pushbutton 5

RD5

Digital I/O

Pushbutton 6

RD6

Digital I/O

Pushbutton 7

RD7

Digital I/O

Pushbutton 8

RE0

Analog input5

Fader 6

RE1

Analog input6

Fader 7

RE2

Analog input7

Fader 8

Table 1. Mapping of controls to the ports of the PIC 18F4550.

Figure 5. Schematic for one group of the Super Retro Fader Box.
(click to see full size)


© 2005 MarkDavid Hosale