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PCA9685 Stopped working?
Moderators: adafruit_support_bill, adafruit

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PCA9685 Stopped working?

by robomike on Fri May 14, 2021 4:37 pm

Hi Support,

I've been through 2 PCA 9685 boards; for some reason, they just stopped working and don't respond via i2c anylonger.

Here is my setup configuration:

VCC and Vin are 5V from Jetson 5V lines
GND is connected to Jetson GND
I have tried both I2c ports on the Jetson, it did work on i2c port 1 before it stopped. that would be pins 3 (SDA) and 5 or on i2c port 0 , that is 27 and 28 where 27 is SDA


I only used the PWM signals to control an external motor driver, not to power a servo or motor.
Please let me know what could be wrong, or if there is a better product to use.

Thanks,

Mike

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Re: PCA9685 Stopped working?

by adafruit_support_bill on Fri May 14, 2021 7:08 pm

VCC and Vin are 5V from Jetson 5V lines

Is the i2c bus on your processor 5v tolerant? Please post a datasheet for the processor you are using.

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Re: PCA9685 Stopped working?

by robomike on Sat May 15, 2021 9:26 am

Yes, I am using the nvidia jetson nano 2gb

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Re: PCA9685 Stopped working?

by adafruit_support_bill on Sat May 15, 2021 9:41 am

Table 18 indicates that level shifting is required for non 3.3v devices: https://www.realtimes.cn/Uploads/downlo ... aSheet.pdf

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Re: PCA9685 Stopped working?

by robomike on Sat May 15, 2021 6:16 pm

Perhaps I am a little confused?

When I provide 3V3 to the VCC logic power the command i2cdetect takes many minutes to run and still does not detect an i2c address.

The adafruit website https://www.adafruit.com/product/815
States that "t is 5V compliant, which means you can control it from a 3.3V microcontroller and still safely drive up to 6V outputs "

My pins are VCC = 3V3, SDA =3 , SCL =5 , GND = GND

But I did as you said and connected a level shifter to the I2c lines and tested , i2cdetect did not detect any address. So I switched VCC to 5V and after several minutes i2cdetect also did not detect an address.

The nano can detect other devices just fine without the level shifter,

My pins for the level shifter were the same, but pin 3 on jetson went to LV and SDA went to HV. and similar for SCL.

I have tried both of my PCA boards and get the identical result.

What is wrong with this PCA board? Or what else am I doing wrong?

robomike
 
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Re: PCA9685 Stopped working?

by robomike on Sat May 15, 2021 6:24 pm

Since I had the level shifter out, I also tried the adalogger i have:

>>> myI2C.try_lock()
True
>>> myI2C.scan()
[]

the PCA was also not found

robomike
 
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Re: PCA9685 Stopped working?

by adafruit_support_bill on Sun May 16, 2021 6:26 am

States that "t is 5V compliant, which means you can control it from a 3.3V microcontroller

A slave device being 5v compliant is not the same thing as your processor being 5v compliant.
If you connect VCC on the PCA9685 to 5v, that puts 5v onto the i2c bus. That exposes your non-5v compliant processor to 5v signals. This is likely to cause damage to your processor's i2c pins.

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Re: PCA9685 Stopped working?

by robomike on Sun May 16, 2021 8:13 am

Hi Support,


I'll restate, the nividia jetson nano and the adafruit adaloggers i2c buses work well with other devices, there is no damage to the pins.

The only issue is with the PCA9685 i2c has stopped working. This means, if used to work perfectly and the next day it stopped working.

How else may we debug the PCA9685?

We have tried multiple host processors, we have tried multiple bus lines, we have tried other i2c devices

robomike
 
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Re: PCA9685 Stopped working?

by adafruit_support_bill on Sun May 16, 2021 8:43 am

If you post some photos and/or a wiring diagram of your system we can take a look for possible causes.

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Re: PCA9685 Stopped working?

by robomike on Sun May 16, 2021 9:10 am

Hello Support!

Here are 3 images:

1. Using a level shifter https://www.dropbox.com/s/4kwv9btch24rb ... 7.jpg?dl=0

2. Without a level shifter (this was first working config) https://www.dropbox.com/s/9my7mxyj29667 ... 3.jpg?dl=0

3. The bottom of the board https://www.dropbox.com/s/c8lnbotkbsi90 ... 0.jpg?dl=0

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Re: PCA9685 Stopped working?

by robomike on Sun May 16, 2021 10:13 am

My apologies, moving VCC to 3V works.

thank you for all of your help, this ticket is now resolved.

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Re: PCA9685 Stopped working?

by adafruit_support_bill on Sun May 16, 2021 10:30 am

Good to hear you have it working. Thanks for the follow-up.

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Please be positive and constructive with your questions and comments.