9.4 KiB
TLC5947
TLC5947 is an Arduino library for the TLC5947, 24 channel 12 bit, PWM device.
Description
This library allows easy control over the 24 channels of a TLC5947 device. Each of the 24 channels provide a 12 bit PWM == 4096 greyscales or levels to be set. This makes the output pretty well tunable. Main purpose is to drive LED's, see datasheet.
To communicate this device uses four IO lines.
- a DATA and CLOCK line to clock in the 288 bits (per device).
- a LATCH line to copy the clocked data to a permanent driver register, which takes care that all 24 channels are updated (nearly) at the same moment.
- a BLANK line to enable/disable all the channels at once.
An interesting feature of the TLC5947 is the automatic thermal safety: – Automatic turns off during over-temperature. – Automatic restart when the temperature returns to normal.
The library is experimental and needs more testing, so please share your experiences. (changes of the interface are definitely possible).
Daisy chaining
Since the version 0.3.0 this library supports daisy chaining. A new constructor takes the number of devices as parameter and an internal buffer is allocated (24 elements per device). This internal buffer is clocked into the devices with write().
Compatible devices
To be investigated.
Related
- https://www.adafruit.com/product/1429
- https://github.com/RobTillaart/TLC5947
- https://github.com/RobTillaart/PCA9634 (I2C)
- https://github.com/RobTillaart/PCA9635 (I2C)
- https://github.com/RobTillaart/PCA9685 (I2C)
Interface
#include TLC5947.h
Constructor
- TLC5947(uint8_t clock, uint8_t data, uint8_t latch, uint8_t blank) constructor. Single device constructor. Defines the pins used for uploading / writing the PWM data to the module. The blank pin is explained in more detail below.
- TLC5947(int deviceCount, uint8_t clock, uint8_t data, uint8_t latch, uint8_t blank) constructor. To be used for multiple devices, typical 2 or more. Defines the pins used for uploading / writing the PWM data to the module. The blank pin is explained in more detail below.
- ~TLC5947() destructor
Base
- bool begin() set the pinModes of the pins and their initial values. The TLC is disabled by default, as the device has random values in its grey-scale register. One must call enable() explicitly.
- int getChannels() return the amount of channels, 24 x number of devices.
- int setPWM(uint8_t channel, uint16_t PWM) Set a PWM value to the buffer to be written later.
channel = 0..23, PWM = 0..4095
Returns TLC5947_OK or TLC5947_CHANNEL_ERROR. - void setAll(uint16_t PWM) set the same PWM value for all channels to the buffer, and writes them to device.
- uint16_t getPWM(uint8_t channel) get PWM value from the buffer, Note this value might differ from device when a new value is set after the last write(). May return TLC5947_CHANNEL_ERROR.
- void write() writes the whole buffer (deviceCount x 24 values) to the device(s).
- void write(int n) writes a part of the buffer (only n values) to the device. Typical used to speed up if less than max number e.g. only 17 channels are used and needs to be updated. (experimental, might have side effects).
write() must be called after setting all PWM values one wants to change. Doing that per channel is far less efficient if one wants to update multiple channels as fast as possible.
Since version 0.3.0 the library has an experimental function write(n) that clocks in only n elements of the buffer. This is useful if one only uses a subset of the channels of the device. This function might have side effects or special applications. If so please let me know.
Percentage wrappers
These are wrapper functions to set the device in percentages. The accuracy of these functions is about 1/4095 = ~0.025%.
Note: the percentages will be rounded to the nearest integer PWM value.
- int setPercentage(uint8_t channel, float percentage) wrapper setPWM().
channel = 0 .. 23, percentage = 0.0 .. 100.0 (will be constrained)
Returns TLC5947_OK or TLC5947_CHANNEL_ERROR. - void setPercentageAll(float percentage) wrapper setAll().
percentage = 0.0 .. 100.0 (will be constrained) - float getPercentage(uint8_t channel) wrapper getPWM().
Note: the error code TLC5947_CHANNEL_ERROR = 0xFFFF will return as 1600%.
Blank line
The blank pin (line) is used to set all channels on or off. This allows to "preload" the registers with values and enable them all at once with very precise timing.
Default a TLC device is disabled (by begin), so one should enable it "manually".
(P13 datasheet)
- void enable() all channels reflect last PWM values written.
- void disable() all channels are off / 0.
- bool isEnabled() returns status of blank line.
The library only supports one enable() / blank line. If you want a separate enable() per device you might need to connect the devices "in parallel" instead of "in series" (daisy chained). The blank parameter in the constructor should be set to -1 (out of range value).
RGB interface
(since 0.2.0)
The 24 PWM channels of the TLC5947 are ideal to control 8 RGB LEDS. The supported mapping of LED to channel is straightforward.
LED n uses channel 3n, 3n+1, 3n+2
| LED | channels | LED | channels | |
|---|---|---|---|---|
| 0 | 0,1,2 | 4 | 12,13,14 | |
| 1 | 3,4,5 | 5 | 15,16,17 | |
| 2 | 6,7,8 | 6 | 18,19,20 | |
| 3 | 9,10,11 | 7 | 21,22,23 |
- int setRGB(uint8_t led, uint16_t R, uint16_t G, uint16_t B)
Set RGB values.
Returns TLC5947_CHANNEL_ERROR if led > 7, TLC5947_OK otherwise. - int getRGB(uint8_t led, uint16_t &R, uint16_t &G, uint16_t &B)
idem.
Returns TLC5947_CHANNEL_ERROR if led > 7, TLC5947_OK otherwise.
If you need an other mapping you have to use the setPWM(channel, pwm) call with the channels of your choice.
Of course one can mix RGB LEDs and single color LEDS but be aware of the hard coded pin mapping for the RGB LEDs.
Performance
Writing 24 x 12 bit takes time, however the library is pretty fast. On a 16 MHz UNO writing all 24 channels takes about 740 microseconds.
Note: time in microseconds.
Note: pre-0.2.0 versions are obsolete, only for completeness.
| platform (MHz) | version | command | time | notes |
|---|---|---|---|---|
| AVR/UNO (16) | 0.1.0 | setPWM() | 16 | 24 channels, obsolete version |
| AVR/UNO (16) | 0.1.0 | write() | 3808 | 24 channels, obsolete version |
| AVR/UNO (16) | 0.1.1 | setPWM() | 16 | 24 channels, obsolete version |
| AVR/UNO (16) | 0.1.1 | write() | 804 | 24 channels, obsolete version |
| ESP32 (240) | 0.1.0 | setPWM() | 6 | 24 channels, obsolete version |
| ESP32 (240) | 0.1.0 | write() | 128 | 24 channels, obsolete version |
| AVR/UNO (16) | 0.2.0 | setPWM() | 16 | 24 channels |
| AVR/UNO (16) | 0.2.0 | setRGB() | 16 | 24 channels = 8 leds |
| AVR/UNO (16) | 0.2.0 | write() | 740 | 24 channels |
| ESP32 (240) | 0.2.0 | setPWM() | 6 | 24 channels |
| ESP32 (240) | 0.2.0 | setRGB() | 8 | 24 channels = 8 leds |
| ESP32 (240) | 0.2.0 | write() | 117 | 24 channels |
Measured with TLC5947_performance.ino.
TODO: Performance 0.3.0 (depends on number of devices, similar to 0.2.0, scales linear)
Future
Must
- update documentation
- links etc.
- schema for multiple devices
- buy hardware
- test test test
Should
- investigate daisy chaining. (hardware needed).
- max CLOCK speed 15 MHz when chained (50% DutyCycle)
- what is clock in practice (e.g. an ESP32 240 MHz)
Could
- add examples
- "dirty" flag for bool writePending()?
- set by setPWM() if value changes.
- would speed up unneeded write() too.
- derived class 8 bits / channel
- saves RAM.
Wont
- investigate how to reduce memory usage (now 48 bytes)
- parameter in constructor # channels? e.g 0..15 (admin overhead).
- could be 36 (12 bits / channel) => performance penalty unpacking!
Support
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Thank you,