![]() ![]() In the next article I will be doing some Voice Recognition, if you are interested see here Raspberry Pi Voice Recognition Works Like Siri Buy the Raspberry Pi from: Banggood | Amazon.Buy the Arduino from: Banggood | Amazon.In this article I will describe how to configure the devices and setup Raspberry Pi as master and Arduino as slave for I2C communication. Also we can just link them directly without a Logic Level Converter. You can easily connect up to 128 slaves with the Pi. Given the fact that there are only 2 USB ports, this is definitely a big advantage. Why do we choose to use I2C? One reason could be it does not use your serial, USB on the Pi. There are many ways of Linking them such as using USB cable and Serial Connection. Please read our Affiliate Link Policy for more information. This helps support the free content for the community on this website. I receive a commission (at no extra cost to you) if you make a purchase after clicking on one of these affiliate links. It is even possible to create a little module that connects inline with the existing wiring/cabling.Some of the links on this page are affiliate links. You hook up the 3v SDA and SCL to the 3v side. The 3v is actually an output from the onboard 3v regulator used for the 3v pullups on the 3v side. The 2 channel ones are great for this type of application. I occasionally do some testing without level shifters, but I always use them for my projects for boards like the esp8266 that are 3v when using 5v i2c devices like PCF8574 based backpacks/LCDs and RTC modules. If you don't want to ever have to deal these types of potential issues, then I'd recommend using a level shifter. Yeah it may not cause any damage on the default i2c pins on DUE when using a single slave with pullups to 5v but, IMO, it is an accident waiting to happen. ![]() Then there is the issue of having to alter the slave devices that have pullups on them to remove the pullup to 5v. you can end up in situations where it works when hooked up to a PC USB port but then fails when hooked up a wall adapter because the supply voltage is different. Things like supply voltage and temperature or even cables can start to affect operation, particularly if using clock rates above the default 100k. It can also create strange issues that can be hard to track down. ![]() Yes it is possible to cheat and not use level shifters and get things to work however, be aware that while this can "work", it doesn't always work since things are not really wired up as they should be which is causing signals to be out of spec on one or both ends. LCD should be fine.īill Perry can probably explain it better !!! Note that an I2C library should NOT enable internal pullups (but it does avoid tears before bedtime) So a Uno owner who has removed external pullups from a backpack will still "work" (but it is out of I2C spec) The Wire library on a Uno enables internal pullups. Even if you have several external pullups you are still within I2C spec. The Ebay onboard pullup modules are handy for a Uno. If you have several Ebay modules with mounted 5V pullups the idle voltages can rise above 3.7V which is bad for the 3.3V Due. Many Ebay I2C modules have mounted pullups. I2C lines are idle at 3.7V (3.6V with 1k0) ![]() In practice, the backpack pullups (if mounted) are 4k7. In theory, you should remove any other pullups e.g. The Due has onboard pullup resistors on its main SDA, SCL pins. ![]()
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