Get weird i2cdetect result with adafruit servo hat


I am trying to use the adafruit servo hat, with gripper/servo.

Hat/Servo isn’t working (program runs happily but servo doesn’t as much as vibrate, let alone turn.

I used these instructions below from the adafruit tutorial

Things that I can imagine being the problem:

A) my soldering. It looks ok but has been years since I used a soldering iron. 2x20 is soldered at top of board. 3x4 motor pins are soldered from under the hat.

B) I have a lcd screen attached, could it be conflicting? Screen still works after adding the hat and Re attaching the jumpers to the top pins. However the pi/lcd screen are connected using gpio1 3v3. And gpio 3 _bcm 2 sDa
And from what I am reading the hat uses gpio 3 and 5 so conflict on gpio 3

C) I get a weird result running sudo i2cdetect -y 1

See attached. It strikes me that there is a problem in I2c setup, i think this says it is detecting on all Chanels. Would a solder bridge be causing that?

power supply is 5v 2amps so should be adequate.

So that you can calibrate the likely location of my failureI am a reasonable python programmer. I can build flashy led python controlled circuits, and use camera for item detection by colour. Software not hardware/ Electronics is my forte.

———————————————— instructions used


Be sure to align the plug with the ground wire (usually black or brown) with the bottom row (edge of board)and the signal wire (usually yellow or white) on the top.

Connect to pi

Begin by having the Pi shutdown and not powered, plug the HAT on top to match the 2x20 headers, and power up the Pi

I2c configure

Interfacing options

Advanced options



Yes (there isn’t a second kernel question asked for my pi version)



1sudo apt-get install python-smbus

2sudo apt-get install i2c-tools

You can then detect if the HAT is found on the #1 I2C port with:

sudo i2cdetect

Once both of these packages have been installed, and i2cdetect finds the 0x40 I2C address, you have everything you need to get started accessing I2C and SMBus devices in Python.

run the following commands from an appropriate location (ex. “/home/pi”):

1sudo apt-get install -y git build-essential python-dev

2git clone

3cd Adafruit_Python_PCA9685

4sudo python install

  1. sudo python examples/

All advice gratefully received

Hi Kim,

It might be worth double checking your soldering, it does appear a bit hit-and-miss

Let me know how you get on!

Thanks. So that I know which pins to focus on, can you advise which ones are essential for the hat/servo purposes (I do get that they all need to be right for general purposes. )

I have been back and resoldered each pin.

I am now getting a straight - - on all pins I.e no detect, rather than ascending numbers on all of them.

All suggestions gratefully received. My current thinking is either contention with the lcd screen, or that I might have fried my gpio pin(S). But unsure how to read result of gpio test.