SX8650 Datasheet, PDF (40/56 Pages) Semtech Corporation – World’s Lowest Power & Smallest Footprint 4-wire Resistive Touchscreen Controller with 15kV ESD

SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
5. Modes of Operation
The SX8650 has four operation modes that are configured using the I2C commands as defined in Table 11 and Table 9.
These 4 modes are:
- manual (command ‘MANAUTO’ and RATE=0),
- automatic (command ‘MANAUTO’ and RATE>0),
- pen detect (command ‘PENDET’),
- pen trigger mode (command ‘PENTRG’).
At startup the SX8650 is set in manual mode.
In the manual mode the SX8650 is entirely stopped except for the I2C peripheral which accepts host commands. This
mode requires RATE equal to be zero (RATE = 0, see Table 9).
In the automatic mode the SX8650 will sequence automatic channel conversions. This mode requires RATE to be larger
than zero (RATE > 0, see Table 9).
In the PENDET mode the pen detection is activated. The SX8650 will generate an interrupt (NIRQ) upon pen detection and
set the PENIRQ bit in the I2C status register. To quit the PENDET mode the host needs to configure the manual mode.
In the PENTRG mode the pen detection is activated and a channel conversion will start after the detection of a pen. The
SX8650 will generate an interrupt (NIRQ) upon pen detection and set the CONVIRQ bit in the I2C status register. To quit
the PENTRIG mode the host needs to configure the manual mode. The PENTRG mode offers the best compromise
between power consumption and coordinate throughput.
5.1. Manual Mode
In manual mode (RATE=0) single actions are triggered by I2C commands. When a command is received, the SX8650
executes the associated task and waits for the next command. It is up to the host to sequence all actions such as: select an
input channel, wait for a settling time, start conversion and read the result. The commands used in manual mode are
typically SELECT and/or CONVERT as defined in Table 10. The CONVERT command should only be used with
CONDIRQ=0.
If the SX8650 is not ready to execute the next command, clock starching occurs. Various timing diagrams show the
operating sequence for examples of the manual mode.
The I2C and the NIRQ are describing the host interface signals. The ‘bias’, ‘sample’ and ‘convert channel(s)’ used on the
following drawings are internal SX8650 signals and shown for illustration only.
5.1.1. CONVERT Command
The CONVERT command will bias the selected channel, wait the time specified by POWDLY and then convert the selected
channel. The converted channel can be one single channel or channels in sequence depending on the CHAN(2:0)
parameter. The reading of the channel(s) can be done over the I2C as described in Figure 31.
An example host I2C sequence for acquisition of the x channel using the CONVERT command is shown in Figure 34 and
Figure 35. The settling time is determined by POWDLY
The init setup could be a I2C write sequence of:
I2CregCtrl1=0x00 // No filter, CONDIRQ = 0
I2CRegChanMsk = 0x80 // Acquisition of the X channel
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 39
www.semtech.com