I have two chips that are connected using two lines. One appears to be the clock line (50% duty cycle), but it doesn't have to be (sometimes constant high). The other line appears to be totally random, but still digital. It might be data.There is a third line between the chips, but it appears to be for something else - it's on a way slower speed and is on another place on the PCB. It also doesn't use a pull-up, while the other two do.How can I find out what protocol (I2C, SPI, RS232, ...) is being used on the lines, if any standard?
Determining communication protocol
communication;pcb
My guess is that the protocol is standard, using a non standard protocol between two devices involves using bitbanging which is not very useful.Let's assume then that the protocol is standard.It's not SPI, SPI needs 4 lines To work. I2C needs two, RS232 needs only two.I don't know what the third line job is, maybe it's used for trigerring/synchronization between the chips.What now ? I would open the data sheet of the microcontroller and see what protocols the chips supports, usually if they are new 32bit SOC, they all support CAN, SPI, USART, etc.Then I would check the pinout of the corresponding lines, to see to which ports they are connected on the chip. This will point you to the exact protocol used.Then connect a logic analyzer, such as this one, which is bundled with a software that can dumo the data transfered acordding to the protocol.