TCA9548

Arduino Library for TCA9548 I2C multiplexer and compatibles.

Description

Library for the TCA9548 and TCA9548a 8 channel I2C multiplexer.

Compatible with PCA9548, PCA9548a, PCA9546, PCA9545, PCA9543.

The library allows you to enable 0 to 7 I2C channels (SDA + SCL) uniquely or simultaneously. In fact the TCA9548 is therefore a switch, although often named a multiplexer. A multiplexer is useful if you have

• multiple identical devices that have a fixed address,
• a too small address range or
• if there are address conflicts between different I2C devices.

The library caches the channels enabled, and if a channel is enabled, it will not be enabled again (low level) to optimize performance.

The device works with 2.3 V to 5.5 V so it should work with most MCU's.

Warning The library is not tested extensively.

I2C

I2C address of the device itself is 0x70 .. 0x77. This address can not be used on any of the I2C channels of course.

Note if your first multiplexer is 0x70, you may have an array of 0x71 multiplexers behind it. (This will give 8 x 8 = 64 I2C buses, a lot of admin overhead and probably performance penalties).

Pull-up resistors are required on all upstream and downstream channels.

The TCA9548 can work up to 400 KHz according to the datasheet.

0.2.0 Breaking change

Version 0.2.0 introduced a breaking change. You cannot set the pins in begin() any more. This reduces the dependency of processor dependent Wire implementations. The user has to call Wire.begin() and can optionally set the Wire pins before calling the TCA9548 begin().

Compatible devices

This library is expected to work for the following devices: (since 0.2.1)

Note: these are not tested with hardware yet, please share your experiences.

There are however small differences, check the data sheets to see the details.

• difference TCA PCA
• https://electronics.stackexchange.com/questions/209616/is-nxps-pca9548a-compatible-with-tis-tca9548a
• https://www.nxp.com/docs/en/application-note/AN262.pdf

Related

• https://github.com/RobTillaart/HC4051 (1x8 mux)
• https://github.com/RobTillaart/HC4052 (2x4 mux)
• https://github.com/RobTillaart/HC4053 (3x2 mux)
• https://github.com/RobTillaart/HC4067 (1x16 mux)

Interface

#include "TCA9548.h"

Constructor

• TCA9548(const uint8_t deviceAddress, TwoWire *wire = &Wire) Constructor. deviceAddress = 0x70 .. 0x77, wire = Wire or WireN.
• bool begin(uint8_t mask = 0x00) set mask of channels to be enabled, default all disabled.
• bool isConnected() returns true if address of the multiplexer is found on I2C bus.

The derived classes PCA9548/PCA9546 have the same interface, except constructor. (see #15)

• PCA9548(const uint8_t deviceAddress, TwoWire *wire = &Wire) Constructor.
• PCA9546(const uint8_t deviceAddress, TwoWire *wire = &Wire) Constructor.
• PCA9545(const uint8_t deviceAddress, TwoWire *wire = &Wire) Constructor.
• PCA9543(const uint8_t deviceAddress, TwoWire *wire = &Wire) Constructor.

Find device

• bool isConnected(uint8_t address) returns true if arbitrary address is found on the current I2C bus + selected channels. This can be used to verify if a certain device is available (or not) on any enabled channel. So it does not scan all (8) channels to see if any of them has a device with the address given.
• bool isConnected(uint8_t address, uint8_t channel) find address on selected channel. Note that this function changes the selected and or enabled channels. Returns true if found.
• uint8_t find(uint8_t address) returns a mask with bits set for channels where the address is found. It scans all channels available. Note that this function changes the selected and or enabled channels. Returns 0 when the address is not found on any channel, or one bit set per channel found.

Channel functions

All "channel functions" return true on success.

• bool enableChannel(uint8_t channel) enables channel 0 .. 7 non-exclusive.
  Multiple channels can be enabled in parallel.
• bool disableChannel(uint8_t channel) disables channel 0 .. 7. Will not disable other channels.
• bool selectChannel(uint8_t channel) enables a single channel 0 .. 7 exclusive.
  All other channels will be disabled in the same call, so not before or after.
• bool isEnabled(uint8_t channel) returns true if the channel is enabled.
• bool disableAllChannels() fast way to disable all channels.

Multiple channels can also be enabled in one call with a mask.

• bool setChannelMask(uint8_t mask) enables 0 or more channels simultaneously with a bit mask.
• uint8_t getChannelMask() reads back the bit mask of the channels enabled.

Reset

Optional the library can reset the device.

• void setResetPin(uint8_t resetPin) sets the pin to reset the chip.
• void reset() trigger the reset pin.

Debug

• int getError() returns the last (I2C) status / error.

Forced IO

When forced IO is set, all writes and read, e.g. uint8_t getChannelMask(), will go to the device. If the forced-IO flag is set to false, it will cache the value of the channels enabled. This will result in far more responsive and faster calls. Note that writes are only optimized if the channels are already set.
Forced IO is also used to speed up getChannelMask().

• void setForced(bool forced = false) set forced write, slower but more robust.
  • forced == false == fast mode (default).
  • forced == true == slower, robust mode.
• bool getForced() returns set flag.

Interrupts

(not tested)

The PCA9545 and PCA9543 support interrupts. These two derived classes have implemented the

• uint8_t getInterruptMask() function that returns a bit mask of interrupts set.

Error Codes

Not implemented yet, preparation for future.

Future

Must

• improve documentation.
• improve error handling.

Should

• add examples.
• test with hardware.

Could

• set an "always enabled" mask.
  • investigate the consequences!
• extend the unit tests.
• uint8_t find(address) returns a mask of channel where address is found
• restore channel in **isConnected(address, channel);
• add guard in reset(), is the pin set?

Wont

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Thank you,