[Bug] Software I2C example not working

[RichardWangPhD]

Problem: I'm able to use your example code to blink the connected LED when using the hardwired I2C connection. However, I am unable to make the LED blink even when using the example code supplied with the library (SoftwareI2CExample).

Circuit setup: Standard setup using Arduino Nano with Adafruit PCA9685 breakout and 10k pull resistors.

Troubleshooting:

• I've ensured that all connections and designated pins for the software I2C are correct, and that the LED is functioning correctly.
• Using the hardwired I2C example (SimpleExample), the LED operates as expected.
• I have checked under an oscilloscope that the designated Software I2C pins are outputting signals, but the PCA9685 chip is not responding.
• The #define PCA9685_ENABLE_SOFTWARE_I2C is uncommented, as instructed.
• I've enabled #define PCA9685_ENABLE_DEBUG_OUTPUT and also used the printModuleInfo() function. I found that under hardwired I2C mode, the Mode1 Register returns 0x20, meaning that only PCA9685_MODE1_AUTOINC is enabled. However, under Software I2C mode, the Mode1 Register returns 0xFF (indeed all Registers return 0xFF), meaning all bits are enabled. This includes bit 4 for SLEEP MODE.
• Using printModuleInfo() before initialisation in hardwired I2C shows NACK error in the Module Info output, which I think is expected as the printModuleInfo() was called before the initialisation. However in software I2C mode shows the same outputs as before, with 0xFF on all bits in all registers.

Thanks!

[NachtRaveVL]

Valid bug, will need to get a looking at this sooner than later for time constraints discussed offline. #20