Configuration¶

Every setting the driver exposes, its default and where it lives: the constructor, run-time calls and the chip state the driver leaves behind.

Constructor¶

pca9685::PCA9685<MyI2c> pwm(&bus, 0x40);

Argument	Type	Meaning
`bus`	`MyI2c*`	Your port; must outlive the driver. `nullptr` makes every call fail
`address`	`uint8_t`	7-bit address, `0x40` to `0x7F` from A0 to A5 (Hardware)

Several chips on one bus: one port object, one driver per address.

Run-time settings¶

Setting	Call	Default	Range
Retries per register access	`SetRetries(int)`	3 (four attempts)	0 or more
Delay between attempts	`SetRetryDelay(void (*)())`	none	Any function with no arguments; a capture-less lambda works
PWM frequency	`SetPwmFreq(float)`	200 Hz (chip default PRE_SCALE = 30)	24 Hz to 1526 Hz
Output driver	`SetOutputDriverMode(bool)`	totem pole	totem pole or open drain
Output inversion	`SetOutputInvert(bool)`	not inverted

The retry settings live in the driver object; the others are chip registers and survive until a power cycle or a software reset.

Chip state after start-up¶

Register	Power-up value	After `EnsureInitialized()`	Changed by
MODE1	`0x11`: SLEEP, ALLCALL	`0x20`: awake, AI on, ALLCALL off	`Reset()`, `SetPwmFreq()`, `Sleep()`, `Wake()`
MODE2	`0x04`: totem pole, change on STOP, OUTNE = 00	unchanged	`SetOutputDriverMode()`, `SetOutputInvert()`
PRE_SCALE	`0x1E` (30): about 200 Hz	unchanged	`SetPwmFreq()`
LEDn_ON / LEDn_OFF	full off (`LEDn_OFF_H` bit 4 = 1)	unchanged	channel calls

Power-up values: Tables 4 to 8 of the datasheet. Because Reset() clears ALLCALL, the chip stops answering the All Call address 0x70 after the driver starts. MODE1.AI (register auto-increment) is set by Reset() and kept by every later MODE1 write, so each four-byte channel write reaches all four registers.

Build options¶

Option or define	Default	Effect
`HF_PCA9685_ENABLE_WARNINGS` (CMake)	`OFF`	`-Wall -Wextra -Wpedantic` on targets that link the driver
`HF_PCA9685_BUILD_TESTS` (CMake)	`OFF`	Host unit tests and documentation snippets
`HF_PCA9685_VERSION_*` (CMake)	`1.0.0`	Set in `cmake/hf_pca9685_build_settings.cmake`, written to `pca9685_version.h`

Next¶

API guide uses these settings in context; Installation shows the CMake setup.