Trimpot, Programming connector, Auxiliary i/o & power outputs – Pololu Orangutan SVP User Manual
Page 10: Servo demultiplexer
Trimpot
The Orangutan SVP comes with a 10 kilo-ohm user trimmer potentiometer, located between the USB connector
and the LCD connector. The trimpot is connected to the auxiliary processor, which measures its output voltage
and reports it to the AVR.
You can disconnect the trimpot from the auxiliary processor by cutting the labeled trace between POT and
ADC/SS on the bottom side of the board. This gives you two options for that line: you can use it as a general-
purpose analog input by connecting some other output to it, or you can connect it to one of your AVR’s free I/O
lines and use it as the SPI slave-select line for the auxiliary processor, allowing you to communicate with some
other SPI peripheral.
Programming Connector
The Orangutan SVP has a 6-pin programming connector on the upper left side. This gives you the option of
using an AVR ISP in-system programmer from Atmel or a compatible programmer, such as our
to program the AVR. This is not necessary, though, because
the Orangutan SVP’s auxiliary processor can serve as an AVR ISP programmer for the AVR.
By default, pin 5 of the Programming connector, which is labeled by an asterisk (*), is connected to the AVR’s
RESET line, which is necessary for ISP programming by an external device). However, you can disconnect those
two pins by cutting a labeled trace on the bottom of the circuit board. This gives you the option of using that line
for some other signal.
Auxiliary I/O & Power Outputs
The Orangutan SVP has five auxiliary I/O lines that are connected to the auxiliary processor. Each I/O line has
associated power and ground connections for easy connections to sensors: the exterior (top) pin is ground, the
middle pin is power (VCC), and the interior (bottom) pin is signal and connects directly to an auxiliary processor
I/O line. The TX line is the serial transmit line. It transmits TTL-level serial bytes received from the computer
on the “Pololu Orangutan SVP TTL Serial Port”. The lines A, B, C, and D/RX can be configured to do different
things. They can function as three analog inputs plus a serial receive line, as four analog inputs, or as the inputs
for two quadrature encoders. See the
section of the Pololu AVR
C/C++ Library for more information.
Servo Demultiplexer
The hardware in the upper-right corner of the Orangutan SVP allows you to control up to 8 servos without
sacrificing a large number of I/O lines or processor cycles. You can control servos using the functions in the
section of the Pololu USB AVR C/C++ library.
The input signal of the demultiplexer is connected to pin PD5 on the AVR. If you are not using PD5 to control
servos, you can use it as a general-purpose digital I/O line or PWM output.
The three output-selection pins of the multiplexer (SA, SB, and SC) are available in the header near the
multiplexer so they can be wired to free I/O lines on the AVR, allowing you to switch between servos. The
output-selection pins have pull-down resistors, so if you have four servos or fewer you can leave some of them
disconnected.
The eight output pins of the multiplexer are available in two 4×3 headers. These lines have current-limiting
resistors on them. Each multiplexer output line has associated power and ground connections for easy connections
to the servos: the exterior (top) pin is ground, the middle pin is power. For each bank of servos, you can configure
which power supply is connected to the power pins, using the provided headers and jumpers. You can power
the servos from VCC, VADJ (see below), or a separate power supply. The fully assembled version ships with a
Pololu Orangutan SVP User's Guide
© 2001–2012 Pololu Corporation
4. Module Pinout and Components
Page 10 of 37