LPC11xx SPI/SSP Problem

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by Coralicious on Fri Mar 15 01:37:34 MST 2013
Hi! I'm using lpc1113/301 for a master-slave communication. Now I'm using as a slave, and I know that Master is sending 3 bytes (0x55, 0xff, 0xff) to me. I can receive them only by setting DSS data to 16-bit (LPC_SSP1->CR0 = 0x070f) but I should receive them also by setting DSS data to 8-bit, so I could send my answer to the master at the same time I receive it's second byte.

The problem is, if I do set DSS data to 8-bit, in my buffer I just receive 0x55, 0x55, 0x55 (the first byte the master sends to me).

When I look to my oscilloscope, I can see on MOSI the 3 data bytes, but in my LED, which I programmed with a toggle to see when does the SSP1_IRQHandler starts, I see that it works each 2 frames of data (each time I've recived the 3 bytes for twice).

What can I do to solve this, so receive 1 byte of data and answer 1 byte just after this?

Sorry for my english