16
votes
Raspberry as an I2C SLAVE
Since this topic is very poorly covered and Sebastião's snippet
and helped me to solve this problem I want add a complete solution on how to setup a RaspberryPi right here (tested on a RPi 3 and Zero ...
- 161
13
votes
Can we use other GPIO pins as I2C
The whole point of I2C is it is a bus. You can therefore connect multiple I2C devices to the same GPIO provided they have different I2C device addresses.
If the devices share an address which can't ...
- 71.5k
13
votes
Pi 4 I/O interface options... and where to find them
The preliminary Raspberry Pi 4 Model B datasheet, section "5.1.1 GPIO Pin Assignments" says:
As well as being able to be used as straightforward software controlled input and output (with ...
- 15.9k
12
votes
Raspberry Pi DPI only works over short distances. Why?
All cables have a length limit. When you exceed that length limit, the signals in the cable attenuate due to resistance of the cable, get deformed due to capacitance and inductance in the cable, and ...
- 991
11
votes
Accepted
Adafruit bonnet & adafruit-circuitpython-motorkit return "ValueError: No Hardware I2C on (scl,sda)=(3, 2)"
The fix is to use raspi-config to activate the I2C port.
I'm documenting this because the interthing had no link from that misleading error message to this fix, because nobody except me forgot to ...
- 338
9
votes
Accepted
How to use Adafruit TCA9548A 1-to-8 I2C Multiplexer Breakout in C#?
A code sample is right there on Adafruit website (in Python, but it's very simple).
The TCA9548A multiplexer is interesting in that it has an I2C address (0x70 by default) - and you basically send ...
- 28.1k
9
votes
Accepted
PoE hat fan activation on OS other than Raspbian
I'm using Ubuntu Server 20.04 LTS. The dtparams setting does not work, instead you need a udev rule.
The fan config is in /sys/class/thermal/cooling_device0/, if you cat /sys/class/thermal/...
- 206
8
votes
Accepted
How to Read I2C Address
The active address is 0x65.
The row indicates the 16's place and the column indicates the one's place. So the answer is 0x60 + 0x05 = 0x65.
- 1,560
7
votes
Accepted
How to setup a MCP79410 real time clock?
In order to set up a MCP79410 real time clock (RTC, see manual), one needs to start by connecting it to one's RPi and a quartz crystal. The following is supposed to be a rough sketch on how to connect ...
- 910
7
votes
Accepted
Raspberry as an I2C SLAVE
This is almost identical to your previous question. You probably should have edited that rather than asking a new question.
You need the bscXfer to be within the while loop. That is how the xfer ...
- 71.5k
7
votes
What is Rpi's I2C Maximum Speed?
As a side note to anyone experimenting with the i2c baudrate, you don't have to set the baudrate via config.txt, which requires a reboot. You can do it at runtime by configuring the kernel module with ...
- 28.1k
6
votes
I2C Bus voltage
Some of the other comments are true, but not totally clear.
You can use the Pi I²C to connect to another I²C device, even if it is powered by 5V provided there are no pull-up resistors to 5V.
I ...
- 61k
6
votes
Accepted
rPi3 I2C-LCD, do i need a logic level converter?
You can't just write to an I2C bus. The SCL line is an output from the master (Pi) but the SDA line is an input and an output.
The LCD should not have pull-ups to 5V on board but many do. Perhaps ...
- 71.5k
6
votes
Accepted
I2C bus 0 not working, I2C bus 1 is
After searching around I have found the problem.
Simple solution is that the config menu only enabled i2c-1 bus, not the i2c busses in general.
Opening the file /boot/config.txt and then adding the ...
- 181
6
votes
Accepted
/dev/mem vs /dev/i2c-1
Disadvantages using /dev/mem for accessing the I²C hardware of the Raspberry Pi directly:
It's not portable to other hardware platforms. It's not portable to additional USB I²C adapters. It's not ...
- 1,728
6
votes
Accepted
What is Rpi's I2C Maximum Speed?
Answer
I have confirmed that Rpi4B 4GB v1.2 buster 2020feb13 I2C #1 can set speed other than 100kHz.
Figures
Appendices
Appendix A - /boot/config.txt tlfong01 2020mar04
# /boot/config.txt ...
- 4,767
6
votes
Accepted
How to connect multiple sensors to an rpi with the I2C?
I2C is a bus system and allows you to connect multiple sensors to the same pins. The master system (the Pi) lets the sensors know who should respond by placing that sensor's address on the bus.
In ...
- 71.5k
5
votes
I2C not working on RPi 2 B
Initially Enable the I2C protocol feature in raspberry pi:
sudo raspi-config
Enable the I2C
Reboot your system
Connect the I2C device to its SDA and SCL pin respectively refer the pin out of ...
- 76
5
votes
Accepted
Prevent wake-from-halt
Yes there is a way to disable GPIO3 (physical pin 5) pulled low to boot.
In /boot/config.txt add the line
dtoverlay=gpio-poweroff
See the documentation for overlays in /boot/overlays/README. The ...
- 66
5
votes
Enable i2c on Ubuntu Mate Raspberry Pi 3
Add the following line to /boot/config.txt
dtparam=i2c_arm=on
Add the following line to /etc/modules
i2c-dev
Reboot
- 71.5k
5
votes
Accepted
Does the Pi4 have pullups on SDA/SCL?
I²C requires pullup to work. The unreferenced discussion seems to be misinformed.
All Pi models have on-board 1.8kΩ pullups on I²C pins 3,5.
I have not used I²C on a Pi4, but assume it is unchanged.
...
- 61k
5
votes
Accepted
Pi locking up trying to use rising/falling edge detection
Solution:
Add:
dtoverlay=gpio-no-irq
to /boot/config.txt.
Previously the kernel would automatically disable interrupts when you set one of rising/falling edge detection methods but that apparently ...
- 195
5
votes
Accepted
How to connect two BME280 sensors via I2C to a Raspberry Pi 3B+
In general, every I2C device has its own address, and one can connect many devices to the same port e.g. of the PI. Individual communication is possible via those addresses. (This is something you set ...
- 516
5
votes
Pi Zero W: Second i2c Bus
Setting up a software I2C bus is very simple with device tree.
For I2C bus 3 using GPIO 5 as SDA and GPIO 6 as SCL add the following entry to /boot/config.txt and then reboot.
dtoverlay=i2c-gpio,...
- 71.5k
5
votes
What is Rpi's I2C Maximum Speed?
The maximum supported speed is 400 Kb/s.
I am not aware of any difference in the I2C implementation between Pi models.
The Broadcom Serial Controller (BSC) controller is a master, fast-mode
(...
- 71.5k
5
votes
What is Rpi's I2C Maximum Speed?
WIth an RPi 4: Using i2cdetect program to make the lines wiggle.
Using an oscilloscope, if I just enable i2c in the config.txt with no other lines in the file, I see 10usec SCL periods (100kHz).
...
- 217
5
votes
Accepted
Does the Raspberry Pi I²C bus support clock stretching?
The Pi 4 appears to support clock stretching on the software I2C bus:
dtoverlay=i2c-gpio,bus=3
The hardware I2C bus is affected by the same bug as earlier models which makes it incompatible with ...
- 28.1k
5
votes
Raspberry Pi DPI only works over short distances. Why?
Your Hyperpixel has a resolution of 800 x 480 x 60fps, so the data rate is 23,040,000 pixels per second, plus some gaps for synchronisation.
You can't send such a fast signal over an arbitrarily long ...
- 597
4
votes
Cannot perform echo command to load driver for rtc module
The problem with your original
echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-1/new_device
command is that only root can write to the /sys/class.. file. Normally prefixing a command with sudo will ...
- 321
4
votes
Meaning of cmd param in write_i2c_block_data
When you issue a block write/read from the Pi with:
bus.write_i2c_block_data(i2c_address, register, list of bytes)
Example:
bus.write_i2c_block_data(80, 0, [49, 50, 51])
or
bus.read_i2c_block_data(...
- 41
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