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pca9555 i2c not responding
I'm using a PCA9555 but having issues utilizing it. It seems like it should be super straight forward. I have A0,A1,A2 connected to ground so i believe that is address 0100 000xb which is 0x20. However when i power up my board i do not see it. I have verified 3.3vdc on pin 24 of the module, verified ground is connected. i have pull up resistors. i should also note that the PCA9555 is before a PCA9685PW which is communicating successfully so i have no reason to suspect an issue with I2C interference. When i scan the bus i see expected devices with correct addresses with exception of the PCA9555. I'm not sure if this is related or not but what i do see are two other individual addresses that are not related to any device on my board. Those are 0x51 and 0x70. I am really unsure if there is something unique about using the PCA9555 that i am missing here so its initialized properly. I have attached my PCB schematic as well as the datasheets for the other I2C components on my board. Any help is seriously appreciated here.
The other I2C modules are as followed with mouser links to their datasheets:
BME280 BME280 Bosch Sensortec | Mouser
PCA9685PW https://www.mouser.com/ProductDetail/NXP-Semiconductors/PCA9685PW112?qs=6YAT8rHPFU9wZqiAeiOMZw%3D%3D
FM24VN10-G FM24VN10-G Infineon Technologies | Mouser
PCA9555PW,112 PCA9555PW,112 NXP Semiconductors | Mouser
VCNL3020-GS08 https://www.mouser.com/ProductDetail/Vishay-Semiconductors/VCNL3020-GS08?qs=FTQF2dEqrCD1ZoO%2F6XyPhA...
TomasVaverka
Hello Travis,
The PCA9555 is compliant with NXP I2C specification for both Standard and Fast modes and I have not heard of other customers reporting such an issue.
I have reviewed the schematic around the PCA9555 and everything seems to be correct. With all address inputs tied to GND, the 7-bit slave address is indeed 0x20 which translates to 0x40 for a write and 0x41 for a read.
There is nothing unique about using the PCA9555, it does not require any specific initialization sequence.
Since you are able to communicate with other slave devices on the bus, it appears to be a HW related issue, could you please double check that the PCA9555 is properly soldered and possibly also try to replace it if you have more devices on hand?
Best regards,
Tomas
