SX8652ICSTRT Semtech, SX8652ICSTRT Datasheet - Page 19

• Manufacturer Part Number: SX8652ICSTRT
• Description: 4/5-wire Resistive Touch Screen Controller (SPI)
• Manufacturer: Semtech

9. Host Interface
The host interfaced is composed of a SPI bus. It performs the read/ write operations on the registers and channels data.
9.1. SPI Read/Write Registers
The WRITE command allows the host to write a single or multiple registers in the SX8652. The host can read single or
multiple registers from the SX8652 by the READ command. This is defined in Table 10.
9.2. SPI Reading Channel Data
Five channels can be sampled by the SX8652: X, Y, Z1, Z2 and AUX. They are defined in Table 12. They can be converted
in sequence with the RegChanMsk register.
The READCHAN command allows the host to read the data obtained after the channels conversion and processing.
The channel data are 12-bit of unsigned format which corresponds to integers between 0 and 4095. This is send on two
bytes, MSB first then LSB. A mask with the value 0x0FFF (4095) must be done to filter the four first unknown bit.
When a channel data has been transmitted, the next one is sent in the successive order: X,Y, Z1, Z2 and AUX. If a channel
has not been converted, the data is not transmitted.
When the channel data buffer gets empty, the data will carry an invalid data as explained in the channel data format.
Remark: After a conversion sequence, it is possible to read only one time the same channel.
Example: the SX8652 is set to convert X and Y. The value 0xC0 is set in RegChanMsk. The first byte read after the
READCHAN command will be X(MSB), then X(LSB), Y(MSB) and at the end Y(LSB). If the host carry on the reading, it will
get invalid data.
Revision V1.7/October 2010
©2010 Semtech Corp.
ADVANCED COMMUNICATIONS & SENSING
W/R command name
W/R command name
READCHAN
WRITE(RA)
READ(RA)
Channel
reserved
reserved
AUX
SEQ
Z1
Z2
X
Y
7
0
0
7
0
2
0
0
0
0
1
1
1
1
CHAN(2:0)
6
0
1
6
0
1
0
0
1
1
0
0
1
1
5
0
0
5
1
Table 11.
Table 12. Channel definition
Table 10.
0
0
1
0
1
0
1
0
1
4
4
x
X channel
Y channel
First channel for pressure measurement
Second channel for pressure measurement
Auxiliary channel
Channel sequentially selected from RegChanMsk register, (see Table 15)
CR(7:0)
CR(7:0)
15kV ESD Low Power 4-Wire / 5-Wire Resistive
Read Channels Data
Page 19
3
3
x
W/R commands
RA(4:0)
RA(4:0)
Touchscreen Controller with SPI Interface
2
2
x
1
1
x
Function
0
0
x
Write register (see Table 14 for RA)
Read register (see Table 14 for RA)
Read data from channel
Function
Function
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