These projects often do not document what version they use. This library has a long history and is used in many projects. The development by owner miguelbalboa has ended.įeature status: complete freeze no function or API change.Ĭode status: partial freeze just fixes/typos or documentation updates no extensions for other boards no new examples. On your Arduino using a RC522 based reader connected via the Serial Peripheralįor advanced and further development please use library RFID_MFRC522v2. Read and write different types of Radio-Frequency IDentification (RFID) cards MySerial.Arduino library for MFRC522 and other RFID RC522 based modules. MySerial.printf("In process_it with rcv_pos = %d\n", main loop - wait for flag set in interrupt routine MySerial.printf("string representation of %2.5f is %s\n", x, val) įor (size_t i = 0 i < sizeof(val) - 1 i++) use dstrtof to produce string version of float value PinMode(PIN_SPI_SS, INPUT_PULLUP) //SS is INPUT for slave device have to send on master in, *slave out* tell slave to get ready for next data transfer MySerial.printf("received %s from slave\n", buf2) Rcvbuf = 0 //add NULL to terminate string MySerial.printf("got %x from Slave\n", c) Serial.println("Receiving Data String\n") MySerial.printf("Sending %x to Slave\n", c) ĭelayMicroseconds(20) //required for arduino-arduino xfrs Then put SPI hardware into Master mode and turn SPI onĭelayMicroseconds(200) //give slave some timeįor (const char* p = "Hello, world!\n" c = *p p++) also put SCK, MOSI into LOW state, and SS into HIGH state. Put SCK, MOSI, SS pins into output mode StreamEx mySerial = Serial //added 03/18/18 for printf-style printing #include //allows printf-style printout syntax The UNO (master) connections are the default pinouts: The circuit and layout is just about as basic as it gets. The program repeatedly transfers a fixed string (“Hello World!”) from the UNO (master) to the Mega 2560 (slave), and then transfers the string version of a float value (3.159) from the slave to the master. In the end though, I think I wrassled it into a reasonable facsimile of a working solution, as shown below. I went through a bunch of iterations, and even more passes through the available documentation. It turns out that SPI between two Arduinos isn’t entirely straightforward, at least not at first. The Mega uses the steering data to adjust wheel speeds to home in on a charging station, so Wall-E2 can continue to roam our house autonomously. As noted above, my intended application is to transfer steering values from my IR detector/demodulator/homing module to the main Mega 2560 microcontroller. Then I moved on to trying to get SPI working for myself. This post was way more than I ever wanted to know about SPI, but it sure is complete! This would have the advantage of making the Teensy independent of the I2C bus, and also give me the chance to play with a part of the Arduino ecosystem that I haven’t used before.Īs usual, I started this process with a lot of Googling, and quickly ran across Australian Nick Gammon’s “ SPI – Serial Peripheral Interface – for Arduino“. In any case, after trying (and failing) to get the I2C bus connection working, I thought I might try an alternate solution and just use SPI between the main controller (Mega 2560) and the IR homing controller (Teensy 3.2). It’s been a while, and I have added some functionality since I originally installed and tested IR homing to the charging station, but it still should all work, right? This worked fine when I last tested it, but now it seems to have taken a vacation. While updating my four wheel autonomous wall-following robot (aka Wall-E2), I ran into a roadblock when I couldn’t get my Teensy 3.2 IR demodulator/tracker module to communicate with the Mega 2560 main microcontroller over I2C.
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