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230 lines
8.5 KiB
Markdown
230 lines
8.5 KiB
Markdown
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[](https://github.com/RobTillaart/TCA9548/issues)
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[](https://github.com/RobTillaart/TCA9548/blob/master/LICENSE)
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[](https://github.com/RobTillaart/TCA9548/releases)
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[](https://registry.platformio.org/libraries/robtillaart/TCA9548)
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# TCA9548
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Arduino Library for TCA9548 I2C multiplexer and compatibles.
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## Description
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Library for the TCA9548 and TCA9548a 8 channel I2C multiplexer.
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Compatible with PCA9548, PCA9548a, PCA9546, PCA9545, PCA9543.
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The library allows you to enable 0 to 7 I2C channels (SDA + SCL) uniquely or simultaneously.
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In fact the TCA9548 is therefore a **switch**, although often named a multiplexer.
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A multiplexer is useful if you have
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- multiple identical devices that have a fixed address,
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- a too small address range or
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- if there are address conflicts between different I2C devices.
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The library caches the channels enabled, and if a channel is enabled,
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it will not be enabled again (low level) to optimize performance.
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The device works with 2.3 V to 5.5 V so it should work with most MCU's.
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**Warning**
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The library is not tested extensively.
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#### I2C
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I2C address of the device itself is 0x70 .. 0x77.
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This address can not be used on any of the I2C channels of course.
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Note if your first multiplexer is 0x70, you may have an array of 0x71 multiplexers behind it.
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(This will give 8 x 8 = 64 I2C buses, a lot of admin overhead and probably performance penalties).
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Pull-up resistors are required on all upstream and downstream channels.
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The TCA9548 can work up to 400 KHz according to the datasheet.
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#### 0.2.0 Breaking change
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Version 0.2.0 introduced a breaking change.
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You cannot set the pins in **begin()** any more.
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This reduces the dependency of processor dependent Wire implementations.
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The user has to call **Wire.begin()** and can optionally set the Wire pins
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before calling the TCA9548 **begin()**.
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#### Compatible devices
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This library is expected to work for the following devices: (since 0.2.1)
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| device | address | channel | interrupt | reset | verified | notes |
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|:---------:|:---------:|:---------:|:-----------:|:-------:|:----------:|:-------:|
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| PCA9543 | 4 | 2 | Y | Y | N |
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| PCA9545 | 4 | 4 | Y | Y | N |
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| PCA9546 | 8 | 4 | | Y | N |
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| PCA9548 | 8 | 8 | | Y | N | equals TCA9648
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| PCA9548 | 8 | 8 | | Y | N | equals TCA9648
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Note: these are not tested with hardware yet, please share your experiences.
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There are however small differences, check the data sheets to see the details.
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- [difference TCA PCA](https://e2e.ti.com/support/interface-group/interface/f/interface-forum/815758/faq-what-is-the-difference-between-an-i2c-device-with-the-family-name-pca-and-tca)
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- https://electronics.stackexchange.com/questions/209616/is-nxps-pca9548a-compatible-with-tis-tca9548a
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- https://www.nxp.com/docs/en/application-note/AN262.pdf
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#### Related
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- https://github.com/RobTillaart/HC4051 (1x8 mux)
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- https://github.com/RobTillaart/HC4052 (2x4 mux)
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- https://github.com/RobTillaart/HC4053 (3x2 mux)
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- https://github.com/RobTillaart/HC4067 (1x16 mux)
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## Interface
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```cpp
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#include "TCA9548.h"
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```
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#### Constructor
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- **TCA9548(const uint8_t deviceAddress, TwoWire \*wire = &Wire)** Constructor.
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deviceAddress = 0x70 .. 0x77, wire = Wire or WireN.
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- **bool begin(uint8_t mask = 0x00)** set mask of channels to be enabled, default all disabled.
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- **bool isConnected()** returns true if address of the multiplexer is found on I2C bus.
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The derived classes PCA9548/PCA9546 have the same interface, except constructor.
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(see #15)
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- **PCA9548(const uint8_t deviceAddress, TwoWire \*wire = &Wire)** Constructor.
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- **PCA9546(const uint8_t deviceAddress, TwoWire \*wire = &Wire)** Constructor.
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- **PCA9545(const uint8_t deviceAddress, TwoWire \*wire = &Wire)** Constructor.
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- **PCA9543(const uint8_t deviceAddress, TwoWire \*wire = &Wire)** Constructor.
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#### Find device
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- **bool isConnected(uint8_t address)** returns true if arbitrary address is found on the
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current I2C bus + selected channels.
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This can be used to verify if a certain device is available (or not) on any **enabled** channel.
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So it does not scan all (8) channels to see if any of them has a device with the address given.
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- **bool isConnected(uint8_t address, uint8_t channel)** find address on selected channel.
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Note that this function changes the selected and or enabled channels.
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Returns true if found.
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- **uint8_t find(uint8_t address)** returns a mask with bits set for channels
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where the address is found. It scans all channels available.
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Note that this function changes the selected and or enabled channels.
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Returns 0 when the address is not found on any channel, or one bit set per channel found.
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#### Channel functions
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All "channel functions" return true on success.
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- **bool enableChannel(uint8_t channel)** enables channel 0 .. 7 **non-exclusive**.
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Multiple channels can be enabled in parallel.
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- **bool disableChannel(uint8_t channel)** disables channel 0 .. 7.
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Will not disable other channels.
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- **bool selectChannel(uint8_t channel)** enables a single channel 0 .. 7 **exclusive**.
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All other channels will be disabled in the same call, so not before or after.
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- **bool isEnabled(uint8_t channel)** returns true if the channel is enabled.
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- **bool disableAllChannels()** fast way to disable all channels.
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Multiple channels can also be enabled in one call with a mask.
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- **bool setChannelMask(uint8_t mask)** enables 0 or more channels simultaneously with a bit mask.
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- **uint8_t getChannelMask()** reads back the bit mask of the channels enabled.
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#### Reset
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Optional the library can reset the device.
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- **void setResetPin(uint8_t resetPin)** sets the pin to reset the chip.
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- **void reset()** trigger the reset pin.
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#### Debug
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- **int getError()** returns the last (I2C) status / error.
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#### Forced IO
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When forced IO is set, all writes and read, e.g. **uint8_t getChannelMask()**, will go to the device.
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If the **forced-IO** flag is set to false, it will cache the value of the channels enabled.
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This will result in far more responsive and faster calls.
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Note that writes are only optimized if the channels are already set.
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Forced IO is also used to speed up **getChannelMask()**.
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- **void setForced(bool forced = false)** set forced write, slower but more robust.
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- forced == false == fast mode (default).
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- forced == true == slower, robust mode.
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- **bool getForced()** returns set flag.
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#### Interrupts
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(not tested)
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The PCA9545 and PCA9543 support interrupts.
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These two derived classes have implemented the
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- **uint8_t getInterruptMask()** function that returns a bit mask of interrupts set.
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## Error Codes
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Not implemented yet, preparation for future.
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| name | value | description |
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|:------------------------|:-------:|:------------------------|
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| TCA9548_OK | 00 | no error |
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| TCA9548_ERROR_I2C | -10 | detected an I2C error |
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| TCA9548_ERROR_CHANNEL | -20 | channel out of range |
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## Future
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#### Must
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- improve documentation.
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- improve error handling.
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#### Should
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- add examples.
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- test with hardware.
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#### Could
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- set an "always enabled" mask.
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- investigate the consequences!
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- extend the unit tests.
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- **uint8_t find(address)** returns a mask of channel where address is found
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- restore channel in **isConnected(address, channel);
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- add guard in **reset()**, is the pin set?
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#### Wont
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## Support
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If you appreciate my libraries, you can support the development and maintenance.
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Improve the quality of the libraries by providing issues and Pull Requests, or
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donate through PayPal or GitHub sponsors.
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Thank you,
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