SX8650 Datasheet, PDF (33/56 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
4.6.5. I2C Read Channels
The host is able to read the channels with a high throughput, by the format shown in Figure 31.
After the start condition [S], the SX8650 Slave Address (SA) is sent, followed by an eighth bit (R=‘1’) indicating a read. The
SX8650 responds with an Acknowledge [A] and the Read Data byte (RD0). The host sends an Acknowledge [A] and the
SX8650 responds with the Read Data byte (RD1). If the host needs to read more data, it will acknowledge [A] and the
SX8650 will send the next read bytes. This sequence can be repeated until the host terminates with a NACK [N] followed
by a stop [P].
The channel data that can be read is defined by the last conversion sequence.
A maximum number of 10 data bytes is passed when all channels (X, Y, z1, z2 and AUX) are activated in the
“I2CRegChanMsk”.
The channel data is sent with the following order: X, Y, Z1, Z2, AUX. The first byte of the data contains the channel
information as shown in Figure 32.
Typical applications require only X and Y coordinates, thus only 4 bytes of data will be read.
S SA R
A RD0 A RD1
A RDn-1 A RDn
NP
Channel (i)
Clock stretching
Channel (i+1)
S:
SA:
R:
A:
N:
RDn:
P:
Start condition
SX8650 Slave Address(7:1)
'1'
Acknowledge
Not Acknowledge (terminating read stream)
Read Data byte(7:0), 0...n
Stop condition
Figure 31. I2C read channels
From host to SX8650
From SX8650 to host
The sampling of the screen by the SX8650 and the host I2C bus traffic are events that might occur simultaneously. The
SX8650 will synchronize these events by the use of clock stretching if that is required. The stretching occurs directly after
the address and read bit have been sent for the I2C read channels command (see Figure 31).
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 32
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