SPI unexpected behavior

Projects Networking, Protocols, and Devices
1

Hi guys,
I'm trying to read some MEMS sensors over SPI using Arduino Due. If I declare the SS pin inside SPI.begin(), I get quite the expected behavior, though sometime it returns me 0xFF. Instead, if I use digitalWrite(), all I get is 0xFF regardless of the ClockDivider or the DataMode. It seems to be related to the SS pin not going low properly.
I currently do not have the possibility to use an oscilloscope.
Do you have any suggestion, like using some pull-ups/pull-downs?
This way it is impossible for me to have a reliable connection. It is simply not working the way it should. The sensor I'm testing is a LPS25HB from ST.
Thanks to everyone

#include <SPI.h>
void setup() {
   SPI.begin(52);
  Serial.begin(115200);
  Serial.setTimeout(200);
  SPI.setClockDivider(52,200);
  SPI.setBitOrder(52,MSBFIRST);
  SPI.setDataMode(52,SPI_MODE0);
  Serial.println("Starting...");
  delay(500);
  SPI.transfer(52,0x0F|0x80, SPI_CONTINUE);
  uint8_t asd=SPI.transfer(52,0x00);
  Serial.println(asd, BIN);
  delay(500);
}

#include <SPI.h>
void setup() {
pinMode(52,OUTPUT);
pinMode(52,HIGH);
   SPI.begin();
  Serial.begin(115200);
  Serial.setTimeout(200);
  SPI.setClockDivider(200);
  SPI.setBitOrder(MSBFIRST);
  SPI.setDataMode(SPI_MODE0);
  Serial.println("Starting...");
  delay(500);
digitalWrite(52,LOW);
  SPI.transfer(0x0F|0x80, SPI_CONTINUE);
  uint8_t asd=SPI.transfer(0x00);
digitalWrite(52,HIGH);
  Serial.println(asd, BIN);
  delay(500);
}

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2

telli:
Hi guys,
I'm trying to read some MEMS sensors over SPI using Arduino Due. If I declare the SS pin inside SPI.begin(), I get quite the expected behavior, though sometime it returns me 0xFF. Instead, if I use digitalWrite(), all I get is 0xFF regardless of the ClockDivider or the DataMode. It seems to be related to the SS pin not going low properly.

digitalWrite(52,LOW);

SPI.transfer(0x0F|0x80, SPI_CONTINUE);
 uint8_t asd=SPI.transfer(0x00);
digitalWrite(52,HIGH);
 Serial.println(asd, BIN);
 delay(500);
}

Ok,
On your second example, your SPI.tranfer(0x0f|0x80,SPI_CONTINUE)
is being interpreted as SPI.transfer(CS=0x8F,value=SPI_CONTINUE,SPI_LAST);

change your example to

digitalWrite(52,LOW);
  SPI.transfer(0x0F|0x80);
  uint8_t asd=SPI.transfer(0x00);
digitalWrite(52,HIGH);
  Serial.println(asd, BIN);
  delay(500);

You were mixing the 'enhanced' and standard mode SPI usage.

Chuck.

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