Review on Geekworm Full Function Motor HAT for Raspberry Pi 4B/3B+/3B - Robot Expansion Board for Raspberry Pi 4 Molde B, 3B+/3B/2B/B+ (Stepper/Motor/Servo/IR Remote) by Ian Welch

I bought two of these devices to use with a Raspberry 4B 8GB RAM microcontroller. Although independent of each other, the two devices worked as intended. When I tried to cascade them over I2C I found that communication with each of them was broken. Using broadcast address 0x70 would both do their job, but I needed to isolate their I2C calls. The i2cdetect clock, which monitors 0x6E and 0x6D (the addresses of the two boards), regularly reported its presence. The Pi also complained from time to time that one or the other board was missing. I bought a third board because the power LED of one of the two devices did not light up, which made me suspicious of its integrity. The third board showed the same I2C problems despite changes to the Pi's baud rate in another try. Replaced the motor driver aspect with two motor drivers from different brands, but chose to keep one of them as a servo driver (and extra motor) option. If 4 possible servos are controlled together, servo jitter will occur despite the operating frequency. Power is not an issue as I am using two 6.5VDC batteries in parallel. Therefore there is no AC noise and the behavior is the same whether both or one battery is used. Servos are not cheap. In general, the product works the same as standalone boards. But I doubt its complex multi-hat addressing.