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AS1115
Datasheet - Typical Application
8x8 Dot Matrix Mode
The application example in
Figure 26
shows the AS1115 in the 8x8 LED dot matrix mode.
The LED columns have common cathodes and are connected to the DIG0:7 outputs. The rows are connected to the
segment drivers. Each of the 64 LEDs can be addressed separately. The columns are selected via the digits as listed
in
Table 6 on page 12
.
The Decode Enable Register (
see page 13
) must be set to ‘00000000’ as described in
Table 8 on page 13
. Single
LEDs in a column can be addressed as described in
Table 11 on page 15
, where bit D0 corresponds to segment G and
bit D7 corresponds to segment DP.
Figure 26. Application Example as LED Dot Matrix Driver
Keyscan
The key readback of the AS1115 can be used either for push buttons as well as switches. If only a single key is
pressed (shorted) at a time no additional diodes are required. If a detection of multiple simultaneous keystrokes is
required diodes within the keypath, as shown in
Figure 27
, are required. Pressing multiple keys without the diodes
would result in ambiguous results. Since KEYA and KEYB have independent inputs only keys on the same path are
affected.
Figure 27. Keyscan Configuration
Note:
If the blink_en bit (bit D4 in the Feature Register 0x0E) is set to ‘1’, the keyscan is not returning a valid value.
Supply Bypassing and Wiring
In order to achieve optimal performance the AS1115 should be placed very close to the LED display to minimize effects
of electromagnetic interference and wiring inductance.
Furthermore, it is recommended to connect a 10μF and a 0.1μF ceramic capacitor between pins V
DD
and GND to
avoid power supply ripple
(see Figure 26)
.
Diode Arrangement
DIG0 to
DIG7
SEG A to G
SEP DP
AS1115
SDA
SCL
IRQ
V
DD
I
SET
SDA
IRQ
GND
SCL
2.7 to 5V
9.53k
Ω
μP
KEYA
KEYB
SEGA
SEGB
SEGC
SEGD
SEG E
SEGF
SEGG
SEGDP
IRQ
Diodes are optional and only required if multiple keystrokes must be
detected simultaneously.
If I2C Self-Adressing is used these two keys cannot be used for read-
back and must be either hard wired opened or shorted.
A short writes a logical “0” whereas an open writes a logical “1” as
address bit.