QTouch acquisition method libraries require 2 GPIO pins per channel. QTouch libraries can be configured to use 1 to 16 channels requiring 2 to 32 pins respectively. There are two options provided for connecting the SNS and SNSK pins.
- 1.
The SNS and SNSK pins are connected to separate ports. ( i.e. Interport)
- 2.
The SNS and SNSK pins are connected to the same port. ( i.e. Intraport)
For 8bit AVR libraries, the following list provides a look at various combinations supported.
When pin configurability is not used:
- 1.
4-channel library – supports up to 4 channels using 4 consecutive pins on different SNS and SNSK ports (or) supports up to 4 channels using 8 consecutive pins on the same port used for both SNS and SNSK lines. This library requires 1 or 2 ports.
- 2.
8-channel library – supports up to 8 channels using 8 consecutive pins on different SNS and SNSK ports (or) supports up to 8 channels using 16 pins spread over two ports (SNS and SNSK are on alternate pins) with SNS1 and SNSK1 pins on the first port and SNS2 and SNSK2 pins on the second port. This library requires 2 ports.
- 3.
12-channel library (available only for 8bit AVR devices) – supports up to 12 channels out of which, 8 channels with 8 consecutive pins for SNS1 and SNSK1 are available on different ports and the other 4 channels with 8 consecutive pins available on the same port for both SNS and SNSK lines. This library requires a total of 3 ports.
- 4.
16-channel library – supports up to 16 channels out of which, 8 channels with 8 consecutive pins for SNS1 and SNSK1 are available on different ports and the other 8 channels with 8 consecutive pins are available on a different pair of SNS2 and SNSK2 ports. This library requires a total of 4 ports.
When pin configurability is used:
- 1.
4-channel library – supports up to 4 channels using any 4 pins on different SNS and SNSK ports (or) supports up to 4 channels using pins on the same port used for both SNS and SNSK lines. This library requires 1 or 2 ports.
- 2.
8-channel library – supports up to 8 channels using 8 pins on different SNS and SNSK ports (or) supports up to 8 channels using pins spread over two ports (SNS and SNSK are on alternate pins) with SNS1 and SNSK1 pins on the first port and SNS2 and SNSK2 pins on the second port. This library requires 2 ports.
- 3.
12-channel library (available only for 8bit AVR devices) – supports up to 12 channels out of which, 8 channels with 8 pins for SNS1 and SNSK1 are available on different ports and the other 4 channels with 8 pins available on the same port for both SNS and SNSK lines. This library requires a total of 3 ports.
- 4.
16-channel library – supports up to 16 channels out of which, 8 channels with 8 pins for SNS1 and SNSK1 are available on different ports and the other 8 channels with 8 pins are available on a different pair of SNS2 and SNSK2 ports. This library requires a total of 4 ports.
- 1.
When a library supports 4 channels using 8 consecutive pins on the same port, the SNS and SNSK pins are allocated alternately. This is valid for all the libraries mentioned above.
- 2.
Usage of intraport configuration requires more code memory than the interport configuration. The values mentioned in the Library_selection_Guide.xls are for interport configurations. The memory consumption for intra-port will be higher to the values mentioned in the Library_selection_Guide.xls
- 3.
The configurations on pin configurability should be used in conjunction with the rules for assigning the pins that are described in section 5.8.2
For UC3 and ATSAM libraries, an n- channel library supports up to n channels using n consecutive pins on different SNS and SNSK ports (or) supports up to n channels using (2*n) consecutive pins on the same port used for both SNS and SNSK lines. This library requires 1 or 2 UC3 or ATSAM ports. In addition to this, for the ATSAM libraries the pins can be configured on 3 ports based on the configuration selected.
Some of the devices in UC3 family has ports having more than 32 pins or less than 32 pins.In those devices, the mapping is given as below:
GPIO Port0 -> A
GPIO Port1 -> B
GPIO Port2 -> C
GPIO Port3 -> X
Example SNS=A and SNSK=X, So channel 0 will be (SNS0 = GPIO0_Pin0 and SNSK0 = GPIO3_Pin0 ).
Similarly,Example SNS=X and SNSK=X, So channel 0 will be (SNS0 = GPIO3_Pin0 and SNSK0 = GPIO3_Pin1 ).
