I'm asking if how can I implement this one. I'm aware about multiple devices being connected over SPI, like having to select individual SS pin for each. Adafruit's CC3000 works fine alone along with the default Adafruit library. CC3000 uses SPI. MFRC522 RFID module by sonmicro (bought at Sparksfun) uses SPI too. It works fine too, independently. But whenever I connect them together, only WiFi works perfectly. I dont want to turn on and off the wifi to make way for the RFID to communicate since it takes some time for it to be connected in a wireless network. I want the two to work synchronously (or having to be scheduled but really fast that's unnoticeable by the user)

here's my code as of now. i cannot post it here as strange things happen i don't know why haha https://drive.google.com/file/d/0B0bZsYo0xMH8YV9uWXJaRFdPT3M/view?usp=sharing

I'm thinking of replacing the RFID with SonMicro's SM130 RFID Module w/ SparkFun Eval board with UART (convertible to I2c) or Adafruit's PN532 with I2c by default. Are these okay to be paired with SPIs like the CC3000? Or should I change CC3000 with the Official WiFi module (UART) or WiFly Module (SPI-to-UART)

1 Answer 1


I couldn't get your code to download so this might be wrong, but it sounds like the modules are running different SPI modes: http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus#Mode_numbers

I had this problem a few years ago. You'd expect SPI to be SPI, but it comes in four different flavours and they won't talk to each other on the same bus. Unfortunately there's no solution but to replace the modules; the Arduino can only run one SPI bus, so can only talk to one of these modules at a time.

However you can run UART and I2C or UART and SPI concurrently by using SoftwareSerial (don't use the native Tx/Rx pins, bad things happen).

So your best bet is to switch to modules that use I2C or UART. Personally I'd use UART, simply for the simplicity of having two separate connections and a higher data rate.

  • thanks for the tip. I'll be trying that. but how would I use UART with SPI? THere are pin assignments that the two share. I'm thinking using of SparkFun's SM130 Eval Board with the CC3000, but CC3000 have SPI so 11,12,13 are exclusive for SPI, although it has ICSP header also for SPI, (would this header make the pins 11,12,13 free?) Oct 31, 2014 at 1:31
  • You can use SoftwareSerial (arduino.cc/en/Reference/softwareSerial) to declare new UART connections from almost any pin (on the Uno, some limitations on other boards). I can't remember if the SPI on the ICSP header is simply the same as pins 11,12,13 or if it's used for the Atmega16U2. Either way it's not going to free up 11,12,13. Oct 31, 2014 at 7:17

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