ADP5585CP-EVALZ Analog Devices, ADP5585CP-EVALZ Datasheet - Page 11

• Manufacturer Part Number: ADP5585CP-EVALZ
• Description: Interface Development Tools LFCSP Evaluation Board
• Manufacturer: Analog Devices
• Series: ADP5585r

Specifications of ADP5585CP-EVALZ

• Rohs: yes
• Product: Evaluation Boards
• Tool Is For Evaluation Of: ADP5585
• Interface Type: I2C
• Operating Supply Voltage: 1.8 V to 3 V
• Factory Pack Quantity: 1

Data Sheet
Use Registers PIN_CONFIG_A[7:0] and PIN_CONFIG_B[7:0]
to configure I/Os for keypad decoding. The number label on
each key switch represents the event identifier that is recorded
if that switch was pressed. If all row/column pins are config-
ured, it is possible to observe all 25 key identifiers on the
FIFO. A larger 6 × 5 matrix can be configured by using the
ADP5585ACBZ-01-R7 or the ADP5585ACPZ-01-R7.
If a smaller 2 × 2 matrix is configured, for example, by using the
C2 and C3 column pins and the R1 and R2 row pins, only the
four event identifiers (8, 9, 13, and 14) can possibly be observed
on the FIFO, as shown in Figure 11.
By default, ADP5585 records key presses and releases on the
FIFO. Figure 12 illustrates what happens when a single key is
pressed and released. Initially, the key scanner is idle. When
Key 3 is pressed, the scanner begins scanning through all
configured row/column pairs. After the scan wait time, the
scanner again scans through all configured row/column pairs
and detects that Key 3 has remained pressed, which sets the
EVENT_INT interrupt. The event counter, EC[4:0], is incre-
mented to 1, EVENT1_IDENTIFIER[6:0] of the FIFO is
updated with its event identifier set to 3, and its
EVENT1_STATE bit is set to 1, indicating a press.
The key scanner continues the scan/wait cycles while the key
remains pressed. If the scanner detects that the key has been
released for two consecutive scan cycles, the event counter,
EC[4:0], is incremented to 2, and EVENT2_IDENTIFIER[6:0]
of the FIFO is updated with its event identifier set to 3. Its
EVENT2_STATE bit is set to 0, indicating a release. The key
scanner returns to idle mode because no other keys are pressed.
The EVENT_INT interrupt can be triggered by both press and
release key events. As shown in Figure 14, if Key 3 is pressed,
EVENT_INT is asserted, EC[4:0] is updated, and the FIFO is
updated. During the time that the key remains pressed, it is
possible for the FIFO to be read, the event counter decremented
to 0, and EVENT_INT cleared. When the key is finally released,
EVENT_INT is asserted, the event counter is incremented, and
the FIFO is updated with the release event information.
EVENT_INT
KEY SCAN
EC[4:0]
KEY 3
KEY 3 RELEASE
KEY 3 PRESS
Figure 12. Press and Release Event
1
0
0
0
FIFO
3
3
0
0
1
2
Rev. C | Page 11 of 40
As shown in Figure 11, the keypad can be extended if each row
is connected directly to ground by a switch. If the switch placed
between R0 and ground is pressed, the entire row is grounded.
When the key scanner completes scanning, it normally detects
Key 1 to Key 5 as being pressed; however, this unique condition
is decoded by the ADP5585, and Key Event 31 is assigned to it.
Up to eight more key event assignments are possible, allowing the
keypad size to extend up to 30. However, if one of the extended
keys is pressed, none of the keys on that row is detectable.
Activation of a ground key causes all other keys sharing that
row to be undetectable.
Ghosting
Ghosting is an occurrence where, given certain key press com-
binations on a keypad matrix, a false positive reading of an
additional key is detected. Ghosting is created when three or
more keys are pressed simultaneously on multiple rows or
columns (see Figure 14). Key combinations that form a right
angle on the keypad matrix can cause ghosting.
The solution to ghosting is to select a keypad matrix layout that
takes into account three key combinations that are most likely
to be pressed together. Multiple keys pressed across one row or
across one column do not cause ghosting. Staggering keys so that
they do not share a column also avoids ghosting. The most
common practice is to place keys that are likely to be pressed
together in the same row or column. Some examples of keys
that are likely to be pressed together are as follows:



EVENT_INT
KEY SCAN
Figure 14. COL0: ROW3 is a Ghost Key Due to a Short Among ROW0, COL0,
EC[4:0]
KEY 3
The navigation keys in combination with Select.
The navigation keys in combination with the space bar.
The reset combination keys, such as CTRL + ALT + DEL.
Figure 13. Asserting the EVENT_INT Interrupt Key Pad Extension
KEY 3 PRESS
ROW0
ROW1
ROW2
ROW3
COL2, and ROW3 During Key Press
1
0
0
0
FIFO
GHOST
3
0
0
0
PRESS
1
READ
FIFO
COL0
0
0
0
0
FIFO
EVENT_INT CLEARED
0
0
0
0
COL1
KEY 32 RELEASE
0
PRESS
PRESS
COL2
ADP5585
FIFO
0
0
0
0
3
0
0
0
1