sx8654 Semtech Corporation, sx8654 Datasheet - Page 20

• Manufacturer Part Number: sx8654
• Description: Haptics Enabled 4/5-wire Resistive Touchscreen Controller With Proximity Sensing
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
In case the range of POWDLY settings available is not enough to cover the required settling time, one can use
the SELECT command first to bias the channel, and then send the CONVERT command hence extending bias
time. SELECT command cannot be used with CHAN=SEQ.
At the end of the conversion(s) bit CONVSTAT will be reset which will trigger NIRQ falling edge (if enabled in
RegIrqMsk). Host can then read channel data which will release NIRQ.
Please note that when the SELECT command is used, the channel is converted whatever the pen status (no pen
detection performed).
4.6.3
In pen detect mode (PENDET) the chip will only run pen detection (continuously when pen is up, regularly as
defined by TOUCHRATE when pen is down) and update PENSTAT bit in RegStat to be able to generate an
interrupt (NIRQ) upon pen detection and/or release. No (touch) conversion is performed in this mode.
To enter PENDET mode the host must set TOUCHRATE > 0 and then send PENDET command.
To quit PENDET mode and stop the touchscreen interface the host must enter MAN mode.
Please note that the next pen detection is not performed as long as NIRQ is low. If the host is too slow and
doesn’t read IrqSrc before next TOUCHRATE tick, no operation is performed and this TOUCHRATE tick is
simply ignored until next one.
4.6.4
In pen trigger mode (PENTRG) the chip will perform pen detection (continuously when pen is up, regularly as
defined by TOUCHRATE when pen is down) and if pen is down, will be followed by a conversion as defined in
RegChanMsk. The chip will update CONVSTAT bit in RegStat and will be able to generate an interrupt (NIRQ)
upon conversion completion. The chip will also update PENSTAT bit in RegStat and will be able to generate an
interrupt (NIRQ) upon pen detection and/or release.
The PENTRG mode offers the best compromise between power consumption and coordinate throughput. To
enter PENTRG mode the host must set TOUCHRATE > 0 and then send PENTRG command. To quit PENTRG
mode and stop the touchscreen interface the host must enter MAN mode.
Rev 1 – 25
PENSTAT
TOUCHRATE
CONVSTAT
I2C Read RegIrqSrc
NIRQ
Channel Conversion
CONVSTAT
NIRQ (RegIrqMsk[3]=1)
Channel Bias
I2C
Pen Detect Mode (PENDET)
Pen Trigger Mode (PENTRG)
tick
Idle
th
July 2011
Figure 21 – Manual Mode – SELECT command (CHAN = Y; PROXSCANPERIOD = 0)
Figure 22 – Pen Detect Mode (RegIrqMsk[3:2] = 11 ; PROXSCANPERIOD = 0)
Pen Detection
Pen Touch
SELECT(Y)
Actual bias time
Resistive Touchscreen Controller with Proximity Sensing
CONVERT(Y)
20
Y
POWDLY
SX8654/SX8655/SX8656
Pen Release
Y
READ CHANNEL
Haptics Enabled 4/5-Wire
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