6.7 KiB
PCA9551
Arduino library for PCA9551 I2C 8 bit PWM LED driver, 8 channel.
Description
This experimental library is to control the I2C PCA9551 PWM extender.
It is derived from the PCA9553 library and kept in sync if possible.
This device has seven possible I2C addresses 0x60 to 0x67, by means of 3 address lines. If you need to connect more PCA9551 devices to a single I2C bus you need a I2C multiplexer like https://github.com/RobTillaart/TCA9548.
The device has two PWM "generators", 0 and 1, and one can set the duty cycle and the frequency by means of a pre-scaler.
Every output channel 0..7 can select to which PWM generator it is connected, or if it is set to ON or OFF.
The output channels can also be used as generic GPIO, however that is not implemented in the first release.
From datasheet
Maximum output sink current is 25 mA per bit and 100 mA per package.
Power-On Reset (POR) initializes the registers to their default state, all zeroes, causing the bits to be set HIGH (LED off).
Related
- https://github.com/RobTillaart/PCA9551 (8 channel)
- https://github.com/RobTillaart/PCA9552 (16 channel)
- https://github.com/RobTillaart/PCA9553 (4 channel)
Follow up series
- https://github.com/RobTillaart/PCA9634 (8 channel)
- https://github.com/RobTillaart/PCA9635 (16 channel)
- https://github.com/RobTillaart/PCA9685_RT (16 channel)
Interface
#include "PCA9551.h"
Constructor
- PCA9551(uint8_t deviceAddress, TwoWire *wire = &Wire) Constructor with I2C device address,
Address = 0x60 .. 0x67 and optional the Wire interface as parameter. - bool begin() initializes the library after startup. Returns true if device address is available on I2C bus.
- bool begin(int sda, int scl) idem, ESP32 ESP8266 only.
- bool isConnected() checks if address is available on I2C bus.
- uint8_t getAddress() returns I2C address.
- uint8_t outputCount() returns the number of channels = 8.
- uint8_t reset()
GPIO
- uint8_t getInput() read all current output levels.
- void pinMode(uint8_t pin, uint8_t mode) set output pin to INPUT or OUTPUT.
- void digitalWrite(uint8_t pin, uint8_t value) set output pin HIGH or LOW.
- uint8_t digitalRead(uint8_t pin) read current state of output pin.
Prescaler Frequency
Get and set the pre-scaler of the PWM generator.
- void setPrescaler(uint8_t gen, uint8_t psc = 255) set pre-scaler for generator, default 255.
- uint8_t getPrescaler(uint8_t gen) get the set value.
gen = 0 or 1
The main oscillator frequency can be divided by a pre-scaler.
The period of BLINK = (PSC + 1) / 44
This gives the output a blink range of 0.172 Hz to 44 Hz.
Some "magic" pre-scalers. (to be confirmed).
| psc | Period | Frequency |
|---|---|---|
| 0 | 0.0227 | 44.00 Hz |
| 1 | 0.0455 | 22.00 Hz |
| 3 | 0.0909 | 11.00 Hz |
| 7 | 0.1818 | 5.50 Hz |
| 10 | 0.250 | 4.00 Hz |
| 21 | 0.500 | 2.00 Hz |
| 43 | 1.000 | 1.00 Hz |
| 87 | 2.000 | 0.50 Hz |
| 175 | 4.000 | 0.25 Hz |
| 219 | 5.000 | 0.20 Hz |
| 255 | 5.818 | 0.172 Hz |
PWM
Get and set the duty cycle of the PWM generator.
- void setPWM(uint8_t gen, uint8_t psc = 128) set PWM for generator, default value = 128.
- uint8_t getPWM(uint8_t gen) get the set value.
gen = 0 or 1
The duty cycle of BLINK = (256 - PWM) / 256
| pwm | Duty Cycle |
|---|---|
| 0 | 0% |
| 64 | 25% |
| 128 | 50% |
| 192 | 75% |
| 255 | 100% |
Note: one might need a Gamma brightness correction - https://github.com/RobTillaart/GAMMA
Output Mode
- uint8_t setOutputMode(uint8_t pin, uint8_t mode) set the mode for
the selected output pin to one of 4 modi operandi.
See table below.
- pin == 0..7, mode == 0..3, see table below.
- returns 0 if OK
- returns error code if parameter is out of range.
- uint8_t getOutputMode(uint8_t led) returns current setting.
- pin == 0..7
- returns mode, see table below.
- returns error code if parameter is out of range.
| Define | Value | Output pin |
|---|---|---|
| PCA9551_MODE_LOW | 0 | is set LOW (LED on) |
| PCA9551_MODE_HIGH | 1 | is set high-impedance (LED off; default) |
| PCA9551_MODE_PWM0 | 2 | blinks at PWM0 rate |
| PCA9551_MODE_PWM1 | 3 | blinks at PWM1 rate |
Power On Reset
The PCA9551 will keep its settings as long as it is powered on. This means it can start with an previous configuration when uploading two different sketches short after each other.
To handle this the library has a reset() function which sets the device in the Power On state.
Error codes
These are kept similar to PCA9635 et al error codes.
| Error code | Value | Description |
|---|---|---|
| PCA9551_OK | 0x00 | Everything went well |
| PCA9551_ERROR | 0xFF | Generic error |
| PCA9551_ERR_WRITE | 0xFE | |
| PCA9551_ERR_CHAN | 0xFD | output pin out of range / channel error |
| PCA9551_ERR_MODE | 0xFC | mode parameter out of range. |
| PCA9551_ERR_REG | 0xFB | |
| PCA9551_ERR_I2C | 0xFA |
Future
Must
- improve documentation
- keep in sync with PCA9553
Should
Could
Wont
Support
If you appreciate my libraries, you can support the development and maintenance. Improve the quality of the libraries by providing issues and Pull Requests, or donate through PayPal or GitHub sponsors.
Thank you,