SPI.transfer() hangs

[cpq]

I am about to use SPI module with my Arduino sketch, but what I noticed that SPI.transfer() hangs for some reason. Here is my sketch:

void setup() {
  Serial.begin(115200);
  while (!Serial) delay(10);

  SPI.begin();

  Serial.println("aa");   // I can see this message
  SPI.transfer(0);
  Serial.println("bb");   // I don't see this message
}

I can see the "aa" in the output, but not the "bb" - apparently SPI.transfer(0) just hangs. I do not have actual SPI hardware connected: testing with the bare, vanilla RP2040 Pico and RP2350 Pico2 boards. Both behave the same.

What am I doing wrong? Advice would be much appreciated. Thank you.

[earlephilhower]

In most modern Arduinos, you need to use SPI transactions. Try adding SPI.beginTransaction() and spi.endTransaction() calls around the transfer(s).

[cpq]

@earlephilhower that was it, thank you so much!