I2c bus


Wolfgang Fahl

Wiring - Raspberry

Color  i2cbus 	Raspberry Pi
yellow SCL     	GPIO 3 / SCL (Pin 5)
orange SDA 	GPIO 2 / SDA (Pin 3)
Red    VCC / V 	3,3V (pin 1)
Black  GND     	GND (Pin 6)

Software - Raspberry

Example with both a SSD1306 and PCA9685 on the bus 

sudo raspi-config
# enable i2c in Interfacing options
sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- 3c -- -- -- 
40: 40 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: 70 -- -- -- -- -- -- --

How many devices on the bus?

https://www.bluedot.space/tutorials/how-many-devices-can-you-connect-on-i2c-bus/

Pull up resistor calculation

It seems recommendations go from 1kΩ (maximize speed) to 10kΩ (minimize power consumption) 4.7 kΩ is a compromise

Wiring - Raspberry[edit]

Color  i2cbus 	Raspberry Pi
yellow SCL     	GPIO 3 / SCL (Pin 5)
orange SDA 	GPIO 2 / SDA (Pin 3)
Red    VCC / V 	3,3V (pin 1)
Black  GND     	GND (Pin 6)

Software - Raspberry[edit]

Example with both a SSD1306 and PCA9685 on the bus 

sudo raspi-config
# enable i2c in Interfacing options
sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- 3c -- -- -- 
40: 40 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: 70 -- -- -- -- -- -- --

How many devices on the bus?[edit]

https://www.bluedot.space/tutorials/how-many-devices-can-you-connect-on-i2c-bus/

Pull up resistor calculation[edit]

It seems recommendations go from 1kΩ (maximize speed) to 10kΩ (minimize power consumption) 4.7 kΩ is a compromise

Stackoverflow[edit]

Most upvoted answer: I include 4K7 resistors in the kit which seems like a reasonable compromise for most users.

Ti.com[edit]

Therefore,we can selectany available resistor value between 966.667Ωand 1.77kΩ. The valueof the pull up resistor can be selected basedon the trade-off for the power consumption and speed. load PDF

Stackoverflow[edit]

Most upvoted answer: I include 4K7 resistors in the kit which seems like a reasonable compromise for most users.

Ti.com[edit]

Therefore,we can selectany available resistor value between 966.667Ωand 1.77kΩ. The valueof the pull up resistor can be selected basedon the trade-off for the power consumption and speed. load PDF

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