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We are using ATtiny25 IC micro controller interfaced with I2C based Capacitive Sensor IS31SE5104.

Schematics

ATtiny25(U1) is programmed with (J1) ISP header (SPI pins used), ATtiny I2C pins are multiplexed with ISP pins as per datasheet and same pins planning to use for interfacing IS31SE5104 (U2).

Is it correct approach? Can we use same ATtiny pins for ISP as well as I2C based sensor IS31SE5104?

Please someone guide, Thanks in advance.

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  • \$\begingroup\$ Yes, it is possible. What will be the default state of pins after reset? \$\endgroup\$ – Umar Dec 21 '16 at 7:12
  • \$\begingroup\$ SDA & SCL will be I2C pins, INTB is input pin (default - High) and low when touch detected, SDB is output pin (default-High) and required low for power down mode. \$\endgroup\$ – Electroholic Dec 21 '16 at 7:19
  • \$\begingroup\$ If I use internal crystal of ATtiny25, can I use XTAL1 and XTAL2 pins for other purpose? \$\endgroup\$ – Electroholic Dec 24 '16 at 6:48
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There is a guide for that from Atmel - AVR042. Look especially at section 4.1.1 .

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ISP pins

As Umar already pointed out, you can use them for other purposes

XTAL1, XTAL2

You can use those also for other purposes if you don't have an external oscillator (see page 60 of the datasheet)

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