Texas Instruments C5535 DSPShield, Справочник по аппаратуре

Страница: 25 / 49

C5535 DSPShield H/W Reference Manual Version 0.1
In Collaboration with Stanford University
page 20
Arduino Interface Voltage Sourcing
JPD JPE
Externally Sourced from Arduino Power Header IOREFF.
IOREF is an input.
Default
SHUNTED OPEN
(Unused)
Internally S5V OPEN
(Unused)
SHUNTED
[1-2]
Internally S3.3V OPEN
(Unused)
SHUNTED
[2-3]
Stand-Alone Mode
Internally S5V. IOREF is an output. SHUNTED
(INPUT)
SHUNTED
[1-2]
Stand-Alone Mode
Internally S3.3V. IOREF is an output. SHUNTED
(INPUT)
SHUNTED
[2-3]
Table 11. Arduino Interface Voltage Source
6.1.2 Analog Inputs
Thee 4 inputs from the Analog Connector are routed to the C5535 DSP’s GPAIN[3:0]
inputs. The analog signal magnitude must be limited to 0 to +1.3V. For protection there
are 100K Ohm series resistors in the input path to limit the input current. They can be
replaced with a different value for specific applications. Additionally, there are Schottky
diodes for clamping the voltage swing to +1.3V and GND. However, it is recommended
to use an input buffer circuit that will limit the input voltage swing by design.
If the Arduino Analog Header is being used only in a pass through mode, it is
recommended that the input series resistors be removed. This disconnects the C5535 DSP
from the Arduino Analog Header and will allow the Arduino Analog pins to safely pass
signals up to 5 volts without damaging the C5535 DSP.
6.2 Arduino/DSPShield Reset Multiplexing
The ARD_RESETN pin on the Arduino Digital Header is the focal point of the
DSPShield’s multiplexing circuitry. The ARD_RESETN is treated as bi-directional
signal that can be controlled by either the Arduino or the C5535 DSP. The different Reset
Modes are illustrated in Figures 8a through 8f.