In the PCB tests log I talked about having the wrong layout for the PCA9685 IC (I used the TTSOP28 pinout with the HVQFN28 package). In order to solve this I considered four options:

• Cross wire and cutting traces to connect the correct pin.
• Buy external PCA chip
• Design breakdown board for the PCA.
• Designing Apsu PCB V2

I kinda wanted to have PWM control as fast a possible because its such a vital part of the ROV. So I opted for the first option of cross wiring the IC, because it could be done within one day (or, so I thought).

Of the total 28 pins of the PCA chip only 9 vital (+4 non vital) pins needed to be rerouted:

Soldering wires on the tiny connections was a frustrating task. The pad of pin 25 (middle pin in the left picture) was even broke due to extensive heat. And I also broke a solder tip (don't ask how). Luckily I managed to solder directly to the IC and connected pin 25, 26 and 27 to VCC. As can be seen on the right picture.

While cutting the traces I however, also cut the I²C-SCL trace. I didn't notice it at first and thought that I blew up the IO pin on my ESP somehow. So I needed an extra wire going from I²C-SCL directly to the ESP (top wire on the picture). After the complete rewiring the PCA now has the address `0b1100111`. And the Adafruit PWM library finally was working properly.

The back of the PCB is really getting seasoned, but I'm very glad the chip is working now. Now I'm off to write a driver.