Now I am looking for some help reference using software serial.
The SIM900 uses pins D7 and D8 for tx/rx software serial, and D9 for powering on.
The Wifi uses pins D8 and D9 for tx/rx software serial.
The GPS has this little breakout to allow me to connect the tx/rx software serial to any digital pin:
So my question is:
Can I just reroute all the software serial pins on each shield to different digital pins without any issue (even though the documentation lists a specific digital pin)?
As in, can I leave the SIM900 to use it's default D7 and D8. Then not plug the Wifi headers into D8 and D9 and reroute them to D5 and D6. Then also doing the same thing to reroute the GPS to D3 and D4.
Giving me software serial pins of:
SIM900 on D7 and D8
Wifi on D5 and D6
GPS on D3 and D4
Giving me all shields on software serial and avoiding the use of D0 and D1.
I have just been informed that I can't use multiple software serials to do this (reliably). Is this true?
Is the only way to do this using a Mega with it's hardware serial ports?
SOLVED:
For those that might stumble upon this with the same question, the answer is that multiple software serials cannot be used reliably and the best option is the use hardware serial ports in this situation.
(Answered in this stack exchange post)
They can be used "reliably" but there are restrictions. You can't listen on more than one SoftwareSerial RX at the same time. If your design can work with that limitation, then it can be reliable.
The AltSoftSerial library has a different set of limitations, which make it useful for certain projects that can't use SoftwareSerial. It's fixed to specific pins (8 and 9 on the Uno) but can work at higher speeds with less impact on the main program speed.
The Arduino/Genuino Micro has an additional hardware serial port but it has other restrictions on SoftwareSerial when you want to add a third. Only certain pins can be used for RX. See the documentation for the details.
