I'm using the NXP LPSPI Sample Code.
It is the same as the code found here:
The problem happens when an LPSPI channel is configured with a high-active Chip Select (kLPSPI_PcsActiveHigh). When enabled it glitches HIGH for 750us prior to the first transfer.
This is because the following code enables the chip select pin, which defaults to low-active, so sets it HIGH. THEN it sets it to high-active, so sets it LOW again:
void LPSPI_MasterInit(LPSPI_Type *base, const lpspi_master_config_t *masterConfig, uint32_t srcClock_Hz)
/* Reset to known status */
/* Set LPSPI to master */
/* Set specific PCS to active high or low */
LPSPI_SetOnePcsPolarity(base, masterConfig->whichPcs, masterConfig->pcsActiveHighOrLow);
Swapping the last two function calls fixes the problem.