MAX11800_1010 Datasheet, PDF (25/59 Pages) Maxim Integrated Products – Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface

Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I²C/SPI Interface
NO
COMMAND
SETUP
X
PANEL
NO
COMMAND
SETUP
Y
PANEL
NO
COMMAND
SETUP
Z
PANEL
TOUCH
DETECT
TIME IS UP
X
DONE AND
DETECT ^CONTINUOUS
Y
ACQUIRE
Z1
ACQUIRE
Z2
ACQUIRE
AUX
DONE AND
ACQUIRE ^CONTINUOUS
AVERAGE
CONVERSION
LAST
CONVERSION
AVERAGE
CONVERSION
LAST
CONVERSION
USER COMMAND
INTERNAL TRANSITION
TOUCH-
DETECT
FINE
PULLUP
Figure 8. State Machine Transitions (Direct Conversion Mode)—MAX11800–MAX11803
TIME IS UP
TOUCH-
DETECT
FINE
PULLUP
Table 6. Measurement and Event Tags
(Continuous Interrupt Mode)
MEASUREMENT
X
Y
Z1
Z2
MTAG[3:2]
00
01
10
11
EVENT
Touch (data valid)
N/A (not used)
No touch present (data invalid)
Measurement in progress (data invalid)
ETAG[1:0]
00
01
10
11
Edge Interrupt Mode
When a touch is present on the panel in edge interrupt
mode, the MAX11800–MAX11803 return to an untimed
high-impedance mode once data tagging operations are
complete. In edge interrupt mode, the duration of a touch
is determined by the tags applied to the measurement
data. Data tagged as initial (00) or midpress (01) indicates
the user needs to continue to scan the panel until a
release is observed. In this state, there is no need to con-
tinue monitoring the touch status prior to the next request-
ed measurement. If a panel touch is not present, data is
tagged as release (10) and the MAX11800–MAX11803
idle in TDM continuously, issuing an interrupt only when
the next panel touch is initiated.
The operation described in the preceding paragraph
makes the edge interrupt mode more power-efficient
than the continuous interrupt mode. However, the edge
interrupt mode requires continuous scanning of the
panel until a release (10) event is observed. Otherwise,
the MAX11800–MAX11803 do not idle in TDM and are
not able to recognize a change in touch status. New
touches are not recognized and new interrupts are not
issued if a release event is not detected before stop-
ping the conversion sequence.
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