I have a 400 KHz device that only works up to 200 KHz on a breadboard. What is the I2C/TWI clock speed in use? While it might be correct for the device, some devices get uppity when used on a breadboard, due to stray capacitance caused by the breadboard. However, the device’s data sheet will have details. Usually a 10K resistor, on each line to VCC is sufficient.

Failing that, I can send you one I wrote.ĭoes the device have its own inbuilt pull up resistors on the SCK and SDA lines? Those two lines must idle in a high state. Time for another stupid question, or two:Īre you certain there’s a device on address 0x37? Have you scanned for one at that address? If you need a scanner, then the Arduino IDE has one in File->Examples->Wire->i2c_scanner. The I2C/TWI stuff uses 7 bit addresses (even if the address fits into 6!) and depending on a read or write action, shifts it up one bit and ORs in a 1 (for read) or a 0 (for write) to the lowest bit, bit 0, giving the two 8 bit addresses, one for reading and one for writing. It actually is a 6 bit address, while the following 0x7F is data. I am aware of the 7 bit address limits and so I believe the 0x37 I am sending is a valid address. Wire.begin() // join i2c bus (address optional for master) All suggestions are welcome and most likely it’s something that I am forgetting although all the sample code I’ve viewed does not show me anything I am missing. I’m working on a development board and my EE says that it looks like a software issue. I’ve tried everything I can think of including setting the clock rate but the second and third byte are no where to be seen. When I run the following code I only see one byte of transmission on an oscilloscope over and over (every 100 ms). I’m having trouble with the wire library. I’m working in Visual Studio Code with the Platform io extension on a Mega 2560. Hi, Last month my password word was stolen from my Arduino account and they have temporarily blocked me out so I thought to post my question here.

Arduino wire library how does it work