Datasheet

ManualsBrandsAdafruit ManualsAdafruitI2C Multiplexer

Adafruit TCA9548A 1-to-8 I2C Multiplexer Breakout

Created by lady ada

Last updated on 2016-11-28 12:25:49 PM UTC

Summary of content (21 pages)

PAGE 1
Adafruit TCA9548A 1-to-8 I2C Multiplexer Breakout Created by lady ada Last updated on 2016-11-28 12:25:49 PM UTC
PAGE 2
Guide Contents Guide Contents Overview Pinouts Power Pins: I2C Control-Side pins: I2C Multiplexed-Side pins: Assembly 2 3 7 7 7 8 9 Prepare the header strip: Add the breakout board: And Solder! 9 10 11 Wiring & Test Example Multiplexing 14 14 Multiple Multplexers Downloads Datasheets Schematic Fabrication Print © Adafruit Industries https://learn.adafruit.
PAGE 3
Overview You just found the perfect I2C sensor, and you want to wire up two or three or more of them to your Arduino when you realize "Uh oh, this chip has a fixed I2C address, and from what I know about I2C, you cannot have two devices with the same address on the same SDA/SCL pins!" Are you out of luck? You would be, if you didn't have this ultra-cool TCA9548A 1-to-8 I2C multiplexer! © Adafruit Industries https://learn.adafruit.
PAGE 4
Finally, a way to get up to 8 same-address I2C devices hooked up to one microcontroller this multiplexer acts as a gatekeeper, shuttling the commands to the selected set of I2C pins with your command. © Adafruit Industries https://learn.adafruit.
PAGE 5
Using it is fairly straight-forward: the multiplexer itself is on I2C address 0x70 (but can be adjusted from 0x70 to 0x77) and you simply write a single byte with the desired multiplexed output number to that port, and bam - any future I2C packets will get sent to that port. In theory, you could have 8 of these multiplexers on each of 0x70-0x77 addresses in order to control 64 of the same-I2C-addressed-part. © Adafruit Industries https://learn.adafruit.
PAGE 6
Like all Adafruit breakouts, we put this nice chip on a breakout for you so you can use it on a breadboard with capacitors, and pullups and pulldowns to make usage a snap. Some header is required and once soldered in you can plug it into a solderless-breadboard. The chip itself is 1.8V - 5V compliant so you can use it with any logic level. We even wrote up a nice tutorial with wiring diagrams, schematics and examples to get you running in 10 minutes! (http://adafru.
PAGE 7
Pinouts Power Pins: Vin - this is the power pin. Since the sensor chip uses 3-5 VDC. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V GND - common ground for power and logic I2C Control-Side pins: SCL - this is the I2C clock pin for the chip itself, connect to your microcontrollers I2C clock line. © Adafruit Industries https://learn.adafruit.
PAGE 8
SDA - this is the I2C data pin for the chip itself, connect to your microcontrollers I2C data line. RST - this is the reset pin, for resetting the multiplexer chip. Pulled high by default, connect to ground to reset A0 A1 A2 - these are the address selection pinsfor the multiplexer. By default the multiplexer is at address 0x70 and these three pins are pulled low. Connect them to Vin to set the address to 0x71 - 0x77.
PAGE 10
Cut the strip to length if necessary. It will be easier to solder if you insert it into a breadboard - long pins down Add the breakout board: Place the breakout board over the pins so that the short pins poke through the breakout pads © Adafruit Industries https://learn.adafruit.
PAGE 11
And Solder! Be sure to solder all pins for reliable electrical contact. (For tips on soldering, be sure to check out our Guide to Excellent Soldering (http://adafru.it/aTk)). © Adafruit Industries https://learn.adafruit.
PAGE 12
You're done! Check your solder joints visually and continue onto the next steps © Adafruit Industries https://learn.adafruit.
PAGE 14
Wiring & Test The TCA9548A multiplexer is interesting in that it has an I2C address (0x70 by default) and you basically send it a command to tell it which I2C multiplexed output you want to talk to, then you can address the board you want to address. We suggest using this little helper to help you select the port #define TCAADDR 0x70 void tcaselect(uint8_t i) { if (i > 7) return; Wire.beginTransmission(TCAADDR); Wire.write(1 << i); Wire.
PAGE 15
On an Arduino, which is what we're using, we suggest running this handy scanner script which will tell you what the breakout detected /** * TCA9548 I2CScanner.pde -- I2C bus scanner for Arduino * * Based on code c. 2009, Tod E. Kurt, http://todbot.com/blog/ * */ #include "Wire.h" extern "C" { #include "utility/twi.h" // from Wire library, so we can do bus scanning } #define TCAADDR 0x70 void tcaselect(uint8_t i) { if (i > 7) return; Wire.beginTransmission(TCAADDR); © Adafruit Industries https://learn.
PAGE 16
Wire.write(1 << i); Wire.endTransmission(); } // standard Arduino setup() void setup() { while (!Serial); delay(1000); Wire.begin(); Serial.begin(115200); Serial.println("\nTCAScanner ready!"); for (uint8_t t=0; t<8; t++) { tcaselect(t); Serial.print("TCA Port #"); Serial.println(t); for (uint8_t addr = 0; addr<=127; addr++) { if (addr == TCAADDR) continue; uint8_t data; if (! twi_writeTo(addr, &data, 0, 1, 1)) { Serial.print("Found I2C 0x"); Serial.println(addr,HEX); } } } Serial.println("\ndone"); } void
PAGE 17
Next up you will have to adjust whatever code you have to select the correct multiplexed port! Make sure before you query from the sensor that you calltcaselect to get the right one #include #include #include
PAGE 18
} void tcaselect(uint8_t i) { if (i > 7) return; Wire.beginTransmission(TCAADDR); Wire.write(1 << i); Wire.endTransmission(); } void setup(void) { Serial.begin(9600); Serial.println("HMC5883 Magnetometer Test"); Serial.println(""); /* Initialise the 1st sensor */ tcaselect(2); if(!mag1.begin()) { /* There was a problem detecting the HMC5883 ... check your connections */ Serial.println("Ooops, no HMC5883 detected ... Check your wiring!"); while(1); } /* Initialise the 2nd sensor */ tcaselect(6); if(!mag2.
PAGE 19
Serial.print("X: "); Serial.print(event.magnetic.x); Serial.print(" "); Serial.print("Y: "); Serial.print(event.magnetic.y); Serial.print(" "); Serial.print("Z: "); Serial.print(event.magnetic.z); Serial.print(" ");Serial.println("uT"); tcaselect(6); mag2.getEvent(&event); /* Display the results (magnetic vector values are in micro-Tesla (uT)) */ Serial.print("Sensor #2 - "); Serial.print("X: "); Serial.print(event.magnetic.x); Serial.print(" "); Serial.print("Y: "); Serial.print(event.magnetic.y); Serial.
PAGE 20
Downloads Datasheets TCA9548A datasheet (http://adafru.it/id8) Fritzing object in the Adafruit Fritzing Library (http://adafru.it/aP3) EagleCAD PCB files on GitHub (http://adafru.it/rzF) Schematic Click to embiggen Fabrication Print © Adafruit Industries https://learn.adafruit.