Mega 4 SPI channels

[PerryBebbington]

Your title suggests you want SPI, your question is about serial, which do you actually need?

A Mega has 4 serial ports, yes. The first of those 4 ports is taken up by the serial monitor, so is not really available unless you really know what you are doing. The other 3 are free for you to use as you please.

There is no problem reading and writing from / to all the serial ports concurrently, serial is a LOT slower than the processor, it will be able to keep up. The only thing is you must write cooperative, non-blocking code, which many people new to writing code struggle to get their heads around. Non blocking means no delay(), no while() and only very short and quick for loops, if any at all.

Here are some tutorials:

Serial Input Basics - updated

Updated Version Please note that this is a revised version of the advice in this earlier Thread which has become very long. As far as possible I have kept the code examples identical or simplifed them slightly. It should not be necessary to refer to the older Thread, but feel free to do so. Contents The following sections are in this Tutorial Introduction Serial data is slow by Arduino standards Example 1 - Receiving single characters Why code is organized into functions Exampl…

Using millis() for timing. A beginners guide

Part 1 It is not usually long before new Arduino users discover that although the delay() function is easy to use it has side effects, the main one of which is that its stops all activity on the Arduino until the delay is finished (not quite true, I know, but that is usually how the problem presents itself). When this occurs the new user is usually directed to the BlinkWithoutDelay example sketch (BWoD) and/or the excellent thread entitled Several things at the same time. Several things at the…

Demonstration code for several things at the same time

NOTE for newcomers. The demo is entirely contained in this Post and Reply #1. There is no need to read further unless you are interested. ...added 25Sep2014 There have been a few occasions recently where newcomers seemed to have difficulty applying the "blink without delay" and "state" concepts to a sketch that is intended to manage a number of concurrent actions. Its very time consuming to respond with suitable code examples - particularly as every case is a little different. I have prepared…