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SPI pins on the DUE are on the central connector labelled 'SPI'. The pinout published for the DUE was changed a couple of days ago after I pointed out to them that they had the SPI pins labelled incorrectly. However, the whole arguement falls down with the simple fact that if you don't call pinMode() at all, the problem doesn't occur. You want to follow the Graynomad pinout diagram.

Otherwise low on its chip select pin means it'll be active. But you should also disable power for the slave. Setting the pin to an input will clear the pullup enable bit, after which you can set the pin to an output and the bit will remain clear. Disable SPI, disable peripheral clock for SPI, change back corresponding pins from alternate functions to normal pin functions and set proper outputs. Therefore, if you call pinMode(X, OUTPUT) before anything else you will end up with the pullup resistor enabled. Point (3) above strongly implies that the instruction is: reg = b'xxxxxx1x' & 'b11111110' If pull-ups are enabled after reset, we can say that on reset: reg = b'xxxxxx1x' For example: PORT_PINCFG_INEN = b'00000001' Thus, we can assume that whichever bit controls input/output is active when asserted, as is the pullup bit. I cannot for the life of me find what value PORT_PINCFG_INEN or PORT_PINCFG_PULLEN are defined as, but they're no doubt just 8-bit masks (they're cast to uint8_t when they're assigned to the 'register'). Not sure if it will fix the problem, so far most of my boards have used the SS pin as an. For example, the Arduino Ethernet shield uses pin 4 to control the SPI connection to the on-board SD card, and pin 10 to control the connection to the Ethernet controller. 36. Unlike other Arduino boards, the SPI pins in the Arduino Due board are broken out on the central 6-pin ICSP header, which makes it physically compatible with. OUTPUT sets a register to reg &= ~PORT_PINCFG_INEN. It is, however, possible to use any pin as the Slave Select (SS) for the devices.INPUT_PULLUP sets a register to reg = (PORT_PINCFG_INEN | PORT_PINCFG_PULLEN).INPUT sets a register to reg = PORT_PINCFG_INEN.Examining the switch/case statement for INPUT vs INPUT_PULLUP vs OUTPUT you see the following: Line 124 defines the pinMode(uint32_t ulPin, uint32_t ulMode) function. Arduino/hardware/arduino/samd/cores/arduino/wiring_digtal.c

If you dig through all the include files you find.

CAN support The Due comes with two CAN (Controller Area Network) buses. These pins support SPI communication using the SPI library. The Due has 54 digital pins, 12 of which support PWM (Pulse Width Modulation). According to the SAM3X/A datasheet,Ĭontrol of the pull-up resistor is possible regardless of theĪfter reset, all of the pull-ups are enabled. The Arduino Due is a microcontroller board based on the Atmel SAM3X8E ARM Cortex-M3 CPU. It might have something to do with the internal pull up resistor.