![]() It is the first Arduino board based on a 32-bit ARM core microcontroller. So make sure you choose another address for them than the addresss you put the Expander (0x70-0x77) on.The Arduino Dueis a microcontroller board based on the Atmel SAM3X8E ARM Cortex-M3 CPU. Make sure that you have no other chip on the chosen address as commands to that chip could be seen as commands to the I 2C expander. Write to (or read from) device connected to bus 1Īs said, the default address of the TCA9548A is 0x70, but can be changed over the range 0x70-0x77. Write to (or read from) device connected to bus 0 ![]() Wire.beginTransmission(0x70) // default TCA9548A addressĪ program thus could look as follows: void setup() It is easiest do to this in a routine: void TCA9548A(uint8_t bus) Its use is quite simple: One only needs to write the required bus nr (0-7) to the Chips address (0x70 by default). The TCA9548A operates on a range of 3 to 5.5 volts, making it suitable for say ‘old’ Arduino 5 Volt logic as well as the new 3V3 logic. This allows you to have up to eight of these modules in your design, adding a total of 64 extra I 2C buses that of course each can address some 128 device The TCA9548A has its own I 2C address of 0x70, which can be changed using three pins. It connects to the existing I 2C port and then can be made to send commands to 1 of 8 different I 2C ports. Instead of a software solution, it is also possible to use an I 2C port expander. These would need some modification to make them work with another I2C library. That is the fact that many existing libraries for I 2C peripherals make direct calls to the “Wire” library. Using those software libraries is a quick and easy way to set up multiple I 2C busses, but there is one major drawback. Some more multiple bus Software I2C libraries can be found here. Software_I2C on GitHub might be akin to this one from Seeedstudio, but I did not make a full comparison. It needs another library called AsyncDelay. SoftWire allows any pins of the Arduino to be used. SoftI2CMaster is a lean I2C implementation. So you will need a library that does allow multiple I 2C objects. ![]() The Wire library doesn’t cater for multiple I 2C busses, you can only call one instance of it. The Wire Library that comes with the Arduino IDE only allows you to use the pins on the Arduino that are meant for I 2C: Board ![]() The only solution is to create multiple I2C busses. So what can we do to use 2 or more I 2C modules that share 0ne address? The Arduino does have one hardware I 2C port, except for the Arduino Due, that has 2. The Adafruit I2C address list shows the I2C addresses of many modules. Even when the chip itself has a possibility to select more than one I2C address, the module does not always implement that (Various PCF8591 modules for instance) ![]() Many I 2C modules can in fact be set for another address, usually through some address jumpers, but that is not always possible. With 128 adresses available you would think you are not going to run into an address conflict, meaning you want to use 2 modules that have the same I2C address, but you’d be surprised. I 2C is a handy protocol to control plenty of chips/sensors/actuators with only 2 pins. ![]()
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