Other Parts Discussed in Thread: TCA9548A
Hi,
In our design we are using a PCA9539PWR. Currently on startup we are seeing some very odd behavior that is undocumented.
For context, our system is using a Nvidia Jetson Orin NX and all I2C transactions are being done by i2cget/i2cset.
According to the hardware design the PCA9539 is configured to respond on address 0x74. However, on power-on we see a device on address 0x70. This device has registers and responds to register changes but does not control any GPIO.
Weirdly, setting this device's register 0x00 to value 0x12 (power on default is 0x11) changes the device address to respond correctly on 0x74. However, this "new" device also does not control gpios correctly. Finally, setting register 0x00 on this new device at 0x74 to value 0x11 gives us 2 devices responding on the bus at 0x70 and 0x74. The device at 0x74 finally functions as documented in the PCA9539 documentation and controls the GPIOs correctly.
Is this behavior as designed? If so, I do not see any mention of this procedure being documented. Ideally we intend to have the linux kernel handle this device and are looking into setting it up to do so.
Please advise on how to fix this if it is an issue.
Thanks,
Akhil M. Birlangi
