I/O Explorer™ USB Reference Manual
Copyright Digilent, Inc. All rights reserved.
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The analog inputs for DAIO port 0 are accessed via connectors JF and J1.
The eight analog input channels accessible through DAIO port 1 are provided by the A/D converter in the
secondary microcontroller. This port supports only single sample input mode. The inputs on this port are available
using the servo connectors S1-S8. These connectors and the corresponding I/O pins on the microcontroller are
shared between DAIO port 0, DPIO port 6, and DEMC port 3.
This analog input port supports two selectable internal voltage references (1.1V and 3.3V) as well as an external
reference that can be applied to the AREF2 pin on connector J5.
The four analog output channels accessible through DAIO port 2 are provided by a Microchip MCP4728 serial D/A
converter. This port supports only single sample output mode. The analog outputs for DAIO port 2 are accessible
via connectors JF and J1.
This analog output port supports two selectable voltage references (2.048V and 3.3V).
7
UART Interface
The I/O Explorer provides a Universal Asynchronous Receiver/Transmiter (UART) interface for asynchronous serial
communications.
The I/O signals for the UART interface are provided on Pmod connector JG. When using the factory firmware, the
UART interface is accessed using the DACI API functions provided in the Digilent Adept SDK and are described in
the DAIO Programmer’s Reference Manual. The UART interface is accessed as DACI port 0.
The signals provided at connector JG are logic level signals. If RS232 signal levels are required, a Digilent
PmodRS232 can be attached to connector JG to provide the level translation and a DB9 connector for connection
to standard RS232 serial devices.
8
RC Servo Connectors
The I/O Explorer provides eight 3-pin RC hobby servo connectors for direct control of servos in embedded
hardware actuator applications. The servo connectors are labeled S1-S8 and are accessible via the Adept system
DEMC servo interface. When programmed directly, the servo connectors are connected to the secondary
microcontroller. The servo connectors S1-S8 are accessible via DEMC port 3.
In addition to the on-board servo connectors, a second servo port, DEMC port 4, provides four additional servo
channels. This servo port can be used with a Digilent servo connector module, PmodCON3, connected to pins 7-12
of Pmod connector JE.
RC servos use a pulse width modulated signal, PWM, to control the servo position. When directly programming
the secondary microcontroller, the servo connectors on the I/O Explorer board are intended to be driven using
timer interrupts rather than directly by the pulse width modulators in the internal timers. Digilent has a reference
design available that illustrates using timer interrupts to control signal timing for the PWM signals to control RC
servos.
