PCF8885 Touch Sensor addressing

[support2]

G'day

I am using PCF8885 touch sensors and I am curious about the addressing structure. Ao is fine I understand that. However when I look at the PCF8885 and pull back the I2C address it tells me that it is 0x21 and indeed when I look at Application Sheet UM10505 and look at the circuit diagram (page 10 of 17) I see two PCF8885's. Also looking at the downloaded code for that example project I see that one is addressed at 0x21 while the other (Slider) is addressed at 0x42?

How is this address change made. Is it through the config command? If a SoftReset is sent does it revert to its original address? Or do these addresses need to be set before the device is deployed into the circuit.

[TomasVaverka]

Hi Paul,

The 7-bit slave address of the PCF8885 is either:

1. 0x20 when A0 = Vss (logic 0). This address must be placed in the upper 7 bits of the first byte and the Read/Write bit is in the LSB. This translates to 0x40 for a write and 0x41 for a read.

2. 0x21 when A0 = Vdd (logic 1). This translates to 0x42 for a write and 0x43 for a read.

I hope it helps!

Best regards,

Tomas

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