ATxmega256A3U Atmel Corporation, ATxmega256A3U Datasheet - Page 75

• Manufacturer Part Number: ATxmega256A3U
• Manufacturer: Atmel Corporation

Specifications of ATxmega256A3U

• Flash (kbytes): 256 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 32 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 50
• Ext Interrupts: 50
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 10
• Twi (i2c): 2
• Uart: 7
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 16
• Adc Resolution (bits): 12
• Adc Speed (ksps): 2000
• Analog Comparators: 4
• Resistive Touch Screen: No
• Dac Channels: 2
• Dac Resolution (bits): 12
• Temp. Sensor: Yes
• Crypto Engine: AES/DES
• Sram (kbytes): 16
• Eeprom (bytes): 4096
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: Yes
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.6 to 3.6
• Operating Voltage (vcc): 1.6 to 3.6
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 7
• Output Compare Channels: 22
• Input Capture Channels: 22
• Pwm Channels: 22
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

6.7.2
8331A–AVR–07/11
QDEC Setup
Figure 6-4.
Figure 6-4
QDPH90 are the two quadrature signals. When QDPH90 leads QDPH0, the rotation is defined
as positive or forward. When QDPH0 leads QDPH90, the rotation is defined as negative or
reverse. The concatenation of the two phase signals is called the quadrature state or the phase
state.
In order to know the absolute rotary displacement, a third index signal (QDINDX) can be used.
This gives an indication once per revolution.
For a full QDEC setup, the following is required:
The following procedure should be used for QDEC setup:
• Thw or three I/O port pins for quadrature signal input
• Two event system channels for quadrature decoding
• One timer/counter for up, down, and optional index count
1. Choose two successive pins on a port as QDEC phase inputs.
2. Set the pin direction for QDPH0 and QDPH90 as input.
3. Set the pin configuration for QDPH0 and QDPH90 to low level sense.
4. Select the QDPH0 pin as a multiplexer input for an event channel, n.
5. Enable quadrature decoding and digital filtering in the event channel.
6. Optional:
7. Set quadrature decoding as the event action for a timer/counter.
8. Select event channel n as the event source for the timer/counter.
a. Set up a QDEC index (QINDX).
b. Select a third pin for QINDX input.
c. Set the pin direction for QINDX as input.
d. Set the pin configuration for QINDX to sense both edges.
e. Select QINDX as a multiplexer input for event channel n+1
f.
g. Select the index recognition mode for event channel n+1.
Set the quadrature index enable bit in event channel n+1.
shows typical quadrature signals from a rotary encoder. The signals QDPH0 and
Quadrature signals from a rotary encoder.
Forward Direction
Backward
Direction
QDPH90
QDPH90
QDINDX
QDINDX
QDPH0
QDPH0
00
01
1 cycle / 4 states
Atmel AVR XMEGA AU
10
11
11
10
01
00
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