PCA9685 wrong initialisation

[gen2thomas]

according to datasheet section "7.3.1.1 Restart mode" the RESET bit must be set after going out of sleep mode (the default) and wait > 500us

adafruit_driver.go

• the sleep bit was reset once with set all other bits to the default --> OK
• wait 5ms --> OK
• reset all bits in MODE1 register by old-state & 0x10, because old-state has sleep unset before, this leads to unset the ALLCALL bit, which was set before by intention
• wait 5ms, but no RESET bit is set --> NOK

pca9685_driver.go

• the sleep bit was reset once with set all other bits to the default --> OK
• wait 5ms --> OK
• the sleep bit is reset again, but not the RESET bit --> NOK

additionally for setting prescaler

• pca9685_driver.go: wrong comment for restore the old mode (e.g. set AI), but just the old value is restored, without knowledge of its content
• adafruit_driver.go: do not set the register before read to MODE1 explicitly

note: the software reset (SWRST) is not the same as setting the RESET bit, it is setting a reserved address by the I2C bus controller

[gen2thomas]

I'm trying to fix this together with #1010

[gen2thomas]

available since v2.2.0