MAX11800_10 Datasheet, PDF (36/57 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
When the MAX11800/MAX11801 operate in autonomous
conversion mode with low or no aperture ranges, the
FIFO and interrupt activity occur frequently with the AP
servicing the devices frequently to avoid loss of data
due to limited FIFO depth. For this reason, do not per-
form autonomous conversion for applications where a
high resolution in either space or time is required. Use
direct conversion mode when requiring a high resolu-
tion in either space or time.
Examples of Using Aperture Mode
Figure 16 shows an example of a touch sequence. A
dragged touch sequence is initiated at position 1 and
continues through to position 5. While multiple samples
are taken during this sequence, only those samples
that meet aperture requirements are enumerated and
are shown with the corresponding aperture ranges.
Positions 6 and 7 show a subsequent momentary press
event.
Figure 16 shows the anticipated interrupt waveforms in
several operating modes. The first waveform shows
interrupt operation assuming that aperture mode is
enabled (with ΔX = ΔY = 4 LSBs), assuming that the AP
service interrupts at a frequency faster than the select-
ed TSC sample rate. Each qualifying sample induces a
FIFO event and an interrupt pulse as shown. Timing
between FIFO events can be timed by the AP to deter-
mine duration information. Table 14 shows the read-
back data assuming that the FIFO does not fill up.
ONE DRAG EVENT (1:5)
PANEL TOUCH SPATIAL WAVEFORM
AND ONE PRESS EVENT (6:7) ^SECOND
16
RELEASE
DRAG
7
APER1
6
APER2
12
INITIAL ₁
DRAG
TOUCH
SECOND
TOUCH
APER6
2
8
5
DRAG
4 _INITIAL
RELEASE
3
4
DRAG
APER4
APER3
0
4
8
12
16
20
24
INTERRUPT TIMING WAVEFORM 1 (ASSUMING FREQUENT SERVICING EVENTS WITH APERTURE MODE ENABLED)
1
2
3
45
6
7
INTERRUPT TIMING WAVEFORM 2 (ASSUMING FREQUENT SERVICING EVENTS WITH APERTURE MODE DISABLED)
1
2
3
45
6
7
INTERRUPT TIMING WAVEFORM 3 (ASSUMING INFREQUENT SERVICING EVENTS)
(1) IRQ ISSUED
(SERVICED) IRQ RELEASED
NOTE: POSITION 5 IS LOGGED EVEN THOUGH POSITION 5 APPEARS IN APER4 BECAUSE POSITION 5 IS A RELEASE DATA POINT.
IT IS THE SAME FOR POSITION 7. IF THE POSITION 6 TOUCH EVENT INITIATES WITHIN THE FINAL APERTURE FROM THE
PREVIOUS EVENT (APER4), POSITION 6 IS LOGGED AS AN INITIAL TOUCH EVENT.
Figure 16. Aperture Usage Example Waveforms
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