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Confusion with I2C addresses
#1
Hi:

I just received the PCA9685 expander but am confused about I2C addresses. With nothing attached to my controller board shows addresses 40, 63 & 70 as present in i2cdetect. Addresses 40 & 70 also appear on my Pi4 which is standalone and not connected to anything; therefore I reckon they are built in to the Pi circuitry for some purpose.

Apparently address 63 belongs to the Reef-Tank controller's built in PCA9685 circuit, although the Reef-Tank manual says it should be configured as address 64. Perhaps that explains why I couldn't get the RS232 custom cable to work with the Power Bar.

When I connect the expander it shows up as address 50.

Could you confirm the correct I2C addresses for both the built in and expander PCA9685 circuits? How should the expander driver be configured?

Thanks for the help.
José

P.S. While I'm happy to help out when I can, I'm not usually able to provide 1:1 assistance via PM's. I would appreciate it if questions are posted to the forum, where not only may other folks benefit from the discussion but also to recruit the assistance of others. Thank you.
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#2
Ah yes those confusing addresses. The reason for the confusion is i2cdetect shows hex values for addresses but reef-pi and most documents talk regular decimal number. I always thought it was an addressing issue for that custom cable because it should have worked.

Address 0x63 = 99 in reef-pi driver, this is the pH circuit.

Address 0x40 = 64 in reef-pi driver, this is the onboard pca9685

Address 0x70 = 112 in reef-pi driver, this is also for pca9685. That address will control all pca9685 in the circuit.

Address 0x50 = 80 in reef-pi driver, this is the expansion.

Here's a calculator for addresses.

https://www.rapidtables.com/convert/numb...tml?x=0x50
[-] The following 1 user Likes Rob F's post:
  • JFReyes
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#3
(02-09-2021, 07:58 PM)Rob F Wrote: Ah yes those confusing addresses. The reason for the confusion is i2cdetect shows hex values for addresses but reef-pi and most documents talk regular decimal number. I always thought it was an addressing issue for that custom cable because it should have worked.

Address 0x63 = 99 in reef-pi driver, this is the pH circuit.

Address 0x40 = 64 in reef-pi driver, this is the onboard pca9685

Address 0x70 = 112 in reef-pi driver, this is also for pca9685. That address will control all pca9685 in the circuit.

Address 0x50 = 80 in reef-pi driver, this is the expansion.

Here's a calculator for addresses.

https://www.rapidtables.com/convert/numb...tml?x=0x50

Thank you for the explanation, Rob!
José

P.S. While I'm happy to help out when I can, I'm not usually able to provide 1:1 assistance via PM's. I would appreciate it if questions are posted to the forum, where not only may other folks benefit from the discussion but also to recruit the assistance of others. Thank you.
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#4
(02-10-2021, 02:10 AM)JFReyes Wrote:
(02-09-2021, 07:58 PM)Rob F Wrote: Ah yes those confusing addresses. The reason for the confusion is i2cdetect shows hex values for addresses but reef-pi and most documents talk regular decimal number. I always thought it was an addressing issue for that custom cable because it should have worked.

Address 0x63 = 99 in reef-pi driver, this is the pH circuit.

Address 0x40 = 64 in reef-pi driver, this is the onboard pca9685

Address 0x70 = 112 in reef-pi driver, this is also for pca9685. That address will control all pca9685 in the circuit.

Address 0x50 = 80 in reef-pi driver, this is the expansion.

Here's a calculator for addresses.

https://www.rapidtables.com/convert/numb...tml?x=0x50

Thank you for the explanation, Rob!

No problem!
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#5
Hi again:

Just tried setting up the PCA9685 expander connected to a Power Bar without success, as no relays clicked. I'll try again using some measuring instruments I have but it would be useful to have proper documentation.

Thanks,
José

P.S. While I'm happy to help out when I can, I'm not usually able to provide 1:1 assistance via PM's. I would appreciate it if questions are posted to the forum, where not only may other folks benefit from the discussion but also to recruit the assistance of others. Thank you.
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#6
Sorry I don't have a manual yet, do you see the I2C address?

Can you post pics of the driver and connectors you added?
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Current time: 03-05-2021, 11:58 PM