Combining an NRF24L01 transmitter/receiver with an Adafruit Motor Shield V1?

Question

I'm making a vehicle project as a way to learn Arduino. I've set up motor control for a number of DC-motors plus a servo via an Adafruit Motor Shield V1 that I picked up.

Everything works fine, but now I've started looking at adding wireless control for the setup using a second Arduino and two NRF24L01 wireless units. However, reading up on the specs for the NRF24L01 it seems it requires pin 12 on the Arduino, which is already in use by the motor shield.

So, can I combine a NRF24L01 and an Adafruit Motor Shield V1? And if so, how?

If it's not possible, what would be the pros and cons of slaving the shielded Arduino to a Nano that would carry the NRF24L01, versus replacing the Adafruit motor shield with external DC motor driver(s)?

Edit:

I now found this previous question:

Motor shield and wireless transceiver compete for same pins

A difference in my project is that I'm not using stepper motors, so perhaps that makes a difference?

Answer 1

One of the problems of the Uno is that the hardware SPI pins conflict with some of the PWM pins. If you want lots of motor control then you have it at the expense of no SPI. If you want SPI then you have it at the cost of reduced motor control.

The V1 shield uses a shift register for some of the motor signals, and that has to fit its signals in around the available PWM pins, so that as well has spilled over into the SPI pins (since you can't use SPI because of the PWM pins that really doesn't matter).

So no SPI means no nRF24L01. Or does it?

You could (though I don't know of any libraries that handle this) use "bit-banged" software SPI on other pins (such as the analog pins) to communicate with the nRF24L01. Your mileage may vary with that, but it is technically possible - as long as you can find (or write) the right software support for it.

Would it be better to throw more hardware at it and have the wireless connection on a dedicated MCU? I would say, yes. Not only does it mean you can use existing libraries to communicate with the nRF24L01 without any worries of conflicting pins, but you get to compartmentalise your software into discrete units that don't interfere with each other. Parallel processing :)

How to communicate between the two? Well, you have I2C available on the analog pins A4/A5, which is well documented and plenty of examples. Or you could use serial, although the 328P's lack of serial ports means that you'd probably be working with SoftwareSerial which is ropy at best. I'd pick I2C out of those two TBH.