Arduino uno spi sck not working

Question

I am trying to verify sck output on my arduino uno. I don't have oscilloscope so I loopbacked miso to sck and tried Executing int rx0=SPI.transfer(5) while printing this using Serial.printrx0) it is giving 255.Whether this is expected output?

• KIIV: I'd expect you'll get all bit with the same value. You can try other SPI_MODES and you probably get 0x00 for two of them.. However you could use loopback between MOSI a MISO (you can expect 1B delay)
• manish kumar: Hi KIIV, THANKS for responding.. I tried all the SPI mode and I got 255 as output, means all the bit as 1 in the byte. Whether it is right result?whether I can say my sck output is normal? Thanks
• Edgar Bonet: You could instead send SCK to T1 (pin 5), configure Timer 1 as a counter, and use it to count the clock pulses.

Answer 1

As suggested by KIIV and myself, you can test the SPI port by:

• connecting MOSI to MISO and checking if you receive what you send
• connecting SCK to the timer input T1 and counting the clock pulses.

Below is a sketch that performs both tests:

/*
 * Test the SPI port.
 *
 * Connect:
 * MOSI (11) to MISO (12)
 * SCK (13) to T1 (5)
 */
void setup() {
 Serial.begin(9600);
 // Configure SPI port.
 DDRB |= _BV(PB2) // SS (digital 10) as output
 | _BV(PB3) // MOSI (digital 11) as output
 | _BV(PB5); // SCK (digital 13) as output
 SPCR = _BV(SPE) // enable port
 | _BV(MSTR); // master mode
 // Configure Timer 1.
 TCCR1A = 0; // normal mode
 TCCR1B = _BV(CS10) // count rising edges of T1 = digital 3
 | _BV(CS11) // ditto
 | _BV(CS12); // ditto
}
void loop() {
 TCNT1 = 0; // clear timer
 uint8_t data = random(256);
 Serial.print(data);
 Serial.print(" -> ");
 SPDR = data; // send
 delay(1);
 if (bit_is_set(SPSR, SPIF)) { // transfer complete?
 Serial.println(SPDR);
 } else {
 Serial.println("nothing received");
 }
 Serial.print(" clock pulses: ");
 Serial.println(TCNT1);
 delay(1000);
}

It should print:

167 -> 167
 clock pulses: 8
241 -> 241
 clock pulses: 8
217 -> 217
 clock pulses: 8
[...]