10 years, 2 months ago.

Bite Swapping

Hello! I am trying to control an AD5791 with and LPC1768. I have been using the mbed platform in this endevour. I ran into a couple issues...It seems that the AD5791 is big endian and the LPC1768 is little endian. Additionally, the AD5791 requires 24-bit words and the LPC1768 can only send 8/16 bit words. Needless to say, I have managed to make some progress...

1. include "mbed.h"

SPI spi(p5, p6, p7); mosi, miso, sclk DigitalOut cs(p8);

int main() { how to insure that 6th place is set (number >> 6) & 1 (via Jared 1/21/14) >>bit shifts to right

Chip must be deselected cs = 1;

Setup the spi for 8 bit data, high steady state clock, second edge capture, with a 1MHz clock rate spi.format(8,1); spi.frequency(50000000);

Select the device by seting chip select low (inverted logic) cs = 0;

Send 0x8f, the command to read the WHOAMI register spi.write(0xAA); spi.write(0xAA); spi.write(0x10);

Send a dummy byte to receive the contents of the WHOAMI register int whoami = spi.write(0x00); int second = spi.write(0x00); int third = spi.write(0x90); printf("WHOAMI register = 0x%X ", whoami); printf("second register = 0x%X ", second); printf("third register = 0x%X ", third); printf("I work.\n");

Deselect the device cs = 1; }

The issue is that when I print whoami, second, and third to the screen I get: 55, 55, and 8. It appears that the bits have been reversed. Does anyone know why this is happening? Or if there is something else awry in my code?

Thank you so much! Natasha