This suggests that SPI.begin() does indeed set those pins to outputs, and if they are not, that SPI.begin() is not actually being called. clocking in a single bit since the lines go directly By doing this AFTER enabling SPI, we avoid accidentally MISO pin automatically overrides to INPUT. ![]() Set direction register for SCK and MOSI pin. automatically switches to Slave, so the data direction of Warning: if the SS pin ever becomes a LOW INPUT then SPI It has a USB host interface to connect with Android based phones, based on the MAX3421e IC. a general purpose output port (it doesn't influence The Arduino MEGA ADK is a microcontroller board based on the ATmega2560. Hi I am working on a project which suppose to get the digitalized values of current and voltage measurements of a battery module. When the SS pin is set as OUTPUT, it can be used as then set it high (to enable the internal pull-up resistor) if the SS pin is not already configured as an output Volatile uint8_t *reg = portModeRegister(port) Set SS to high so a connected chip will be "deselected" by default NoInterrupts() // Protect from a scheduler and prevent transactionBegin Here is where the Arduino SPI library begin method sets SS, SCK and MOSI as outputs: void SPIClass::begin() What is the evidence that there are no signals on the SPI pins? Please use code tags when posting code ("" button on editor).ĭo you have a good reason for leaving the parentheses out from the call to SPI.begin()? PinMode(MOSI, OUTPUT) //If I comment this line MOSI gives no output. PinMode(SCK, OUTPUT) // If I comment this line, SCK gives no output PinMode(SS, OUTPUT) //Avoid being in SPI Slave mode which apparently can happen if this pin is an Input. Initalize the CS chip select pin on the MCP4110 digital pot take the chip select high to de-select: take the chip select low to select the device: SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE0)) SPI interface to MCP4110 Digital Pot to control the IR LED intensity So any other ideas why SPI.begin may not be setting SCK and MOSI to OUTPUT mode? #include ![]() ![]() I also confirmed that the SS, SCK and MOSI constants all point to their respective pins (53, 52, 51) using Serial.print. So is the SPI library not recognizing that I have a MEGA 2560 for some reason? (I've set the Processor type in the Tools menu) The SPI library docs do say this is necessary for the SS pin, but senior forum members have categorically said that SPI.begin handles this automatically for SCK and MOSI, but that doesn't seem to be the case for me. Otherwise there're absolutely no signals on those pins. After lots of troubleshooting I've discovered that even when using SPI.begin I still need to set the SS, SCK and MOSI pins to outputs myself.
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