Teensy: SPI and Pressure Sensor

Question

I'm first time working with a Teensy 3.1. I have to connect this (MS5803-01BA: http://www.amsys.de/products/ms5803.htm) pressure sensor via SPI to my Teensy.

My problem is, that I don't have any reliable knowledge on SPI. I read the Wikipedia for it and also the Teensy-Manual.

For the pressure sensor I already got a C-Code but it is only working with the ATMEL ATmega644p microcontroller. I tried to get the code to work with my Teensy, but it seems like I don't get either any input nor any output.

I hope that one of you can help me with the following code and tell me what I'm missing out on. Thank you.

Code:

http://pastebin.com/xaWXfRUR

Datasheet of the pressure sensor:

http://www.amsys.de/sheets/amsys.de.ms5803_01b.pdf

C-Code for the pressure sensor for the ATMEL ATmega644p microcontroller: http://www.amsys.de/sheets/amsys.de.an520_e.pdf

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PS: Please excuse my not perfect English for it's not my native language.

Answer 1

Details about SPI at SPI - Serial Peripheral Interface - for Arduino

This isn't right:

  SPI.transfer(CMD_ADC_READ); // send ADC read command
  SPDR = SPI.transfer(0x00); // send 0 to read 1st byte (MSB)
  ret = SPDR;
  temp = 65536 * ret;
  SPDR = SPI.transfer(0x00); // send 0 to read 2nd byte
  ret = SPDR;
  temp = temp + 256 * ret;
  SPDR = SPI.transfer(0x00); // send 0 to read 3rd byte (LSB)

The SPI library handles SPDR for you. Writing to it yourself will corrupt its behaviour.

It should be more like:

  SPI.transfer(CMD_ADC_READ); // send ADC read command
  ret = SPI.transfer(0x00); // send 0 to read 1st byte (MSB)
  temp = 65536 * ret;
  ret = SPI.transfer(0x00); // send 0 to read 2nd byte
  temp = temp + 256 * ret;
  ret = SPI.transfer(0x00); // send 0 to read 3rd byte (LSB)

Ditto for elsewhere.