I have, in former lives, used TWI (I2C) in a number of applications (non-AVR) with no problem. That applies more to the use of the AVR as a slave, but you DO need to be VERY careful about the state of that pin when SPI is in operation. If it is an ADC, then, at the very least, it will require the clock, an enable, and MISO (Master In Slave Out), If you need to write to ADC control registers, then MOSI would also be needed. Which one you use depends on whether it is a write-only, a read-only, or a read-write device. Most SPI peripherals require a clock, an enable, and at least one data connection. And if operating in the UART in SPI mode, it looks like you then use pins RX0, TX0, and XCK? If in this mode, can I still use MOSI and MISO and SCK as general purpose I/O pins? Or would that interfere with the SPI? Any help in understanding SPI or recommendation on the simplest serial communication method would be greatly appreciated. does it also need SS? I wasn't exactly sure from reading the datasheet.

Is this the case? I'm just looking for the most reliable & easy to code option between those 3 choices.Īlso, it looks like the SPI needs the: MOSI, MISO, and SCK pins. I was hoping, although not at all sure, that perhaps the UART in SPI Mode would be as easy & glitch free as doing normal UART communication. I have zero experience with SPI communication or doing the UART in SPI mode communication. It eventually seemed to run okay, but always left me worried as to when the next lock-up was gonna strike. It left a really bad taste in my mouth after the weeks I spent working with it & getting those kind of results.

might get on a good run sometimes & work fine for hours straight, or might get in a bad mood another day and keep locking up the processor every other call, or fail to initialize, etc. On the other hand, I have spent hours and hours and hours trying to make I2C communication work, and it always seemed very glitchy & erratic. I have done UART communication many times in the past and found it very easy to implement & always ran glitch free.

simplest, most reliable, etc.) and also make sure I am connecting to the right pins for each. Before making a PCB to connect with one set of pins or another, I just wanted to ask everyone's opinion on which communication method is preferred. and have found both SPI and I2C devices available. I'm trying to select a 12-bit A/D converter to interface with my ATMega644.

I2c vs uart performance