Radio plus sensor on the SPI bus

[dbemowsk]

I am wondering if it is possible to use two devices on the SPI bus. My nodes use nRF24L01+ radios which run on the SPI BUS. I am wondering if it is possible to add a sensor that would also use the bus?

[Yveaux]

@dbemowsk should work just fine.
Beware that when using mySensors with message queuing, the other spi device driver must use SPI transactions.

[dbemowsk]

@Yveaux Thanks, that is what I was hoping to hear. I have not done a lot with SPI communications, so I am still learning this end of arduino. This is what I am trying to connect: https://www.digikey.com/products/en?mpart=AS5047P-TS_EK_AB&v=961

Thanks for the quick response.

[Yveaux]

@dbemowsk you will be quite busy! That link gives 5473963 Results :laughing:

[dbemowsk]

@Yveaux which link are you referring to?

[Yveaux]

@dbemowsk but I guess you mean the as5047p, correct?
If this is for your weather station you could also just take an earth magnetic field sensor to determine the angle of rotation of a rotating magnet. Much cheaper, available as module, very sensitive, but requires a little math to get the actual angle.

[Yveaux]

@dbemowsk said in Radio plus sensor on the SPI bus:

@Yveaux which link are you referring to?

The digikey link

[dbemowsk]

@Yveaux said in Radio plus sensor on the SPI bus:

That link gives 5473963 Results

I am not sure where you are seeing these results. The link I posted was to a part listed on the DigiKey website.

[dbemowsk]

it is an AS5047P magnetic rotation sensor.

[Yveaux]

@dbemowsk This is what I get when clicking the link on my mobile:

On a PC the sensor is correctly shown...

[dbemowsk]

This is what I see on my machine:

[Yveaux]

@dbemowsk Digikey walks in mysterious ways... (on mobile browsers at least...)

[dbemowsk]

@Yveaux So I see.

This is the part I purchased though.

I got it on ebay with the breakout board, magnet, header connector, and the person threw in a spare chip. I am using it for my wind direction sensor for my weather station project.

This is a library I found for it. https://github.com/smellsofbikes/AS5047_arduino_library

[dbemowsk]

@Yveaux said in Radio plus sensor on the SPI bus:

when using mySensors with message queuing, the other spi device driver must use SPI transactions.

Do you have any links to some information on using transactions?

[Yveaux]

@dbemowsk https://www.arduino.cc/en/Reference/SPI

Basically, SPI transfers in the driver need to be enclosed in

SPI.beginTransaction(...)
...
SPI.endTransaction()

[dbemowsk]

@Yveaux Sounds simple enough. Thanks for all the help.

[dbemowsk]

So I have this set up for testing on my UNO. Uusing the library from here https://github.com/smellsofbikes/AS5047_arduino_library, this is the sample code I am running.

#include "AS5047.h"
#include <SPI.h>

AS5047 myAS5047(10); // SS pin
void setup()
{
  SPI.begin;
  Serial.begin(9600);
}

void loop()
{
  long value;
  value=(360*myAS5047.sensor_read())/16383;
  Serial.print("measured value: ");
  Serial.println(value);
  delay(1000);
}

Using the code as written, it works perfectly giving me a reading between 0 and 360 as I rotate the direction sensor. Two questions I have though.

First, When I migrate this over to my platform on my easy newbie board, the SS pin (defined on line 4), which as I understand is acting as a CS or chip select, should be on something other than 10 because the nRF24 is on 10 and each device should have its own CS, but if I change it to another pin on my UNO and change line 4 to match the pin that I put it on, it doesn't work. Is this because I need an SPI device on pin 10 first taking care of the SS or slave select?

My second question would be, how would I write this using transactions?

[dbemowsk]

Comment number 7 of this post http://forum.arduino.cc/index.php/topic,19770.0.html was the basis for part of my last question.

[Yveaux]

@dbemowsk the library you're using says 'untested' in the readme, and that looks to be true :smile:
The pin mode of _ss is set to input in the constructor of AS5047.cpp which doesn't seem correct. Try setting it to output and see what happens.

[dbemowsk]

@Yveaux Works perfect now, thanks. Now I just need to research calling this as a transaction. Just brainstorming a bit, I will most likely have a function written to grab the value from the sensorand begin and end the transaction there, but since I have never worked with transactions, I will need to research how to write the code to do that.