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AT90USBKEY2

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Using the AT90USBKey
AT90USBKey Hardware User Guide 2-7
7627A–AVR–04/06
2.2.2 VBUS Generator
When using the AT90USB microcontroller in USB host mode, the AT90USBKey should
provide a 5V power supply over the VBUS pin of its USB mini AB connector.
A couple of transistors allows the UVCON pin of the AT90USB to control the VBUS
generation (See Figure 2-3). In this mode the AT90USBKey is powered by external
battery power supply source.
Figure 2-3 . VBUS generator schematic
2.2.3 “POWER-ON“ LED
The POWER-ON LED (“D1”) is always lit when power is applied to AVRUSBKey
regardless of the power supply source.
R25
100k
Q1
BC847B
-
C19
4.7uF
R24
10k
M1
FDV304P/FAI
UVCON
VBUS
5V
Using the AT90USBKey
2-8 AT90USBKey Hardware User Guide
7627A–AVR–04/06
2.3 Reset
Although the AT90USB has its on-chip RESET circuitry (c.f. AT90USB Datasheet,
section “System Control and Reset), the AVRUSBKey provides to the AT90USB a
RESET signal witch can come from two different sources:
Figure 2-4 . Reset Implementation
2.3.1 Power-on RESET
The on-board RC network acts as power-on RESET.
2.3.2 RESET Push Button
By pressing the RESET push button on the AVRUSBKey, a warm RESET of the
AT90USB is performed.
2.3.3 Main Clock XTAL
To use the USB interface of the AT90USB, the clock source should always be a crystal
or external clock oscillator (the internal 8MHz RC oscillator can not be used to operate
with the USB interface). Only the following crystal frequency allows proper USB
operations: 2MHz, 4MHz, 6MHz, 8MHz, 12MHz, 16MHz. The AT90USBKey comes with
a default 8MHz crystal oscillator.
RST
VCC
R6
47k
C8
220nF
RESET
Using the AT90USBKey
AT90USBKey Hardware User Guide 2-9
7627A–AVR–04/06
2.4 On-board Resources
2.4.1 USB
The AVRUSBKey is supplied with a standard USB mini A-B receptacle. The mini AB
receptacle allows to connect both a mini A plug or a mini B plug connectors.
Figure 2-5 . USB mini A-B Receptacle
When connected to a mini B plug, the AT90USB operates as an “USB device” (the ID
pin of the plug is unconnected) and when connected to a mini A plug, the AT90USB
operates as a “USB host” (the ID pin of the A plug is tied to ground).
2.4.2 Joystick
The 4+1 ways joystick offers an easy user interface implementation for a USB
application (it can emulate mouse movements, keyboard inputs...).
Pushing the push-button causes the corresponding signal to be pulled low, while
releasing (not pressed) causes an H.Z state on the signal. The user must enable
internal pull-ups on the microcontroller input pins, removing the need for an external
pull-up resistors on the push-button.
Figure 2-6 . Joystick Schematic
C7
1uF
VBUS
R4 0
GND
VBUS
1-V_BUS
3-D+
2-D-
4-ID
5-GND
SHIELDSHIELDSHIELDSHIELD
USB_MiniAB
J3
VBUS
VBUS
GND
R3 22
R2 22
D+
D-
UID
CR1
CR2
UCAP
Select
5
Left
7
Up
3
Right
6
Down
4
Com1
1
Com2
2
SW3
TPA511G
PE[7..0]
PB[7..0]
PB5
PB6
PB7
PE4
PE5
Select
5
Left
7
Up
3
Right
6
Down
4
Com1
1
Com2
2
SW3
TPA511G
PE[7..0]
PB[7..0]
PB5
PB6
PB7
PE4
PE5
Select
5
Left
7
Up
3
Right
6
Down
4
Com1
1
Com2
2
SW3
TPA511G
PE[7..0]
PB[7..0]
PB5
PB6
PB7
PE4
PE5
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AT90USBKEY2

Mfr. #:
Buy AT90USBKEY2
Manufacturer:
Microchip Technology / Atmel
Description:
Development Boards & Kits - AVR AVR USB Eval Kit
Lifecycle:
New from this manufacturer.
Delivery:
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