SPI1 multiple byte transfer on Teensy LC

[wjszlachta]

Hi there, I have been trying to benchmark the SPI bus on my Teensy LC and reproduce some of the results in:

https://forum.pjrc.com/threads/27689-Teensy-LC-Beta-Testing/page3
https://github.com/manitou48/DUEZoo/blob/master/SPIperf.txt

I switched from SPI to SPI1 to get 24 MHz clock, but I couldn't get SPI1 transfer(void *buf, size_t count) to work with my code - the function hangs on the last line in SPI.h:

inline static void transfer(void *buf, size_t count) {
  ...
  *p = SPDR;
}

Looking at the sources in benchmark:

https://github.com/manitou48/teensy3/blob/master/spi1perf.ino

the implementation of spi1_transfer(void *buf, size_t count) is identical to transfer(void *buf, size_t count) apart from the last line, where:

inline static void transfer(void *buf, size_t count) {
  ...
  *p = SPI1_DL;
}

I replaced *p = SPDR with *p = SPI1_DL in transfer(void *buf, size_t count) of SPI1Class and everything seems to be working correctly as far as I can tell.

Many thanks!

P.S.
If that helps, I seem to recall that transfer(void *buf, size_t count) in SPIClass (not SPI1Class) works correctly.