Digilent I/O Explorer Referentiehandleiding - Pagina 6

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I/O Explorer™ USB Reference Manual

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).

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.

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.

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