About reading CY8C9540 Expander Device ID register

[aemiroglu]

I am trying to read Device ID register data by making i2c communication with STM32 from the CY8C9540 expander sensor I have.  While reading the Device ID 0x2e register address, I am reading wrong data and I could not find much while examining what I can do about this situation.

I connected the AO pin directly to VSS pin. To do strong pull down.

XRES pin connected to GND.

VSS pin connected to GND.

WD pin connected to GND. (I left selectable. It can also be drawn to 5V.)

XRES pin floating. Could this pin be causing the problem.

Is it a problem not to throw a resistor while doing a strong pull down of the A0 pin?

I am open to your suggestions.

[Gautami_12]

Hi @aemiroglu ,

"CY8C9540 expander sensor"

Which sensor are you using?

Please go through the thread.

Warm Regards,
Gautami J

[aemiroglu]

https://www.infineon.com/dgdl/Infineon-CY8C9520A_CY8C9540A_CY8C9560A_20-_40-_and_60-Bit_I_O_Expander...

Isn't the CY8C9540 a 40-Bit I/O expander?

[SampathS_11]

Hello @aemiroglu ,

What address are you using for slave?

Best regards,

Sampath

[aemiroglu]

Hello,

Thank you for your return. Since the A0 pin is strong pull down, that is, GND is made with the VSS pin, the slave address I use is 0x20.

[SampathS_11 · Accepted solution]

Hello @aemiroglu ,

Address 0x20 is correct. Are you getting an ACK from the slave after sending 0x2E register address? If the hardware connections and the devices are OK, you should get the correct ID.

Best regards,

Sampath

[aemiroglu]

Problem solved, thank you for everything @SampathS_11