topic Re: PCA9698 the problem with the two expanders in Other NXP Products

PCA9698 the problem with the two expanders

Sergio0703 — Sat, 22 Mar 2025 06:44:53 GMT

In my case, there are two expanders on the line that should simultaneously update the status of pins according to a STOP state. The documentation states that access to each circuit must be accompanied by the RESTART signal, and there must be a final STOP signal. However, in my case only the second expander is updating the pin status, while the first one is ignoring it. It seems that the first expander does not see the STOP signal.

Re: PCA9698 the problem with the two expanders

guoweisun — Mon, 24 Mar 2025 06:19:17 GMT

HI Sergio0703

1: Please share with your schematic.

2: please also catch some waveforms for your test issue and show the IIC signals.

Re: PCA9698 the problem with the two expanders

Sergio0703 — Mon, 24 Mar 2025 11:38:23 GMT

1000008422.png

1000008424.jpg

Re: PCA9698 the problem with the two expanders

guoweisun — Tue, 25 Mar 2025 12:44:30 GMT

Please follow below steps:

Example 2: More than one PCA9698 is used on the I2C-bus and all the outputs need to

change at the same time.

OCH bit (Mode Selection Register, bit 1) must be equal to ‘0’ in all the devices.
The master device must access the devices one-by-one.
Access to each device must be separated by a Re-START command
When all the devices have been accessed, the master must generate a STOP

command.

At the STOP command, all the PCA9698s that have been accessed will update their

Output Port registers that have been programmed and change the output states all at

the same time.

Re: PCA9698 the problem with the two expanders

Sergio0703 — Tue, 25 Mar 2025 12:58:57 GMT

Everything was done according to the documentation, which is what the waveform shows. However, the first expander (before RESTART) does not see the STOP sent after the message to the second expander. I haven't found any contradictions in the I2C specification, so I don't understand the reason.

Re: PCA9698 the problem with the two expanders

guoweisun — Fri, 28 Mar 2025 00:36:47 GMT

1:For your test procedure please list clear steps by steps below and catch the waveforms:

OCH bit (Mode Selection Register, bit 1) must be equal to ‘0’ in all the devices.
The master device must access the devices one-by-one.
Access to each device must be separated by a Re-START command
When all the devices have been accessed, the master must generate a STOP

command.

2: You can give the more detail schematic.

Thanks!

Re: PCA9698 the problem with the two expanders

Sergio0703 — Tue, 08 Apr 2025 07:12:36 GMT

From what was not present in the last waveform, I send the MODE setting for the register with OCH set to 0.
1000009018.jpg
PCA9698 Addr 0x4E
1000009020.jpg
PCA9698 Addr 0x4A

Re: PCA9698 the problem with the two expanders

Sergio0703 — Tue, 08 Apr 2025 07:15:44 GMT

1000009019.jpg

Schematic