topic Re: Lpc1796 ssp/ssi in LPCXpresso IDE

Lpc1796 ssp/ssi

lpcware — Thu, 16 Jun 2016 02:53:42 GMT

Content originally posted in LPCWare by timer on Thu Jan 26 16:36:24 MST 2012
Hello,

I try to read with SSI (SSP) from an Sensor. With my Oszi I can see the data is comming but I dont find all the 16bits.

Actually I this routine with Length = 1 because the I get one clock-"burst" with 16 periodes.

void SSP1Receive(uint8_t *buf, uint32_t Length )
{
uint32_t i;

    for (i=0; i<Length; i++)
    {
        // send a dummy byte, read the result
        LPC_SSP1->DR = 0xFF; // send 0xFF as dummy

        /* Wait until the Busy bit is cleared */
        while ( (LPC_SSP1->SR & (SSPSR_BSY|SSPSR_RNE)) !=  SSPSR_RNE );
        *buf++ = LPC_SSP1->DR;
    }
    return;
}

This Code is form the SSP-Example but I get as you may expect only one 8bit value in the buffer.
But I need 16bit. I try to change the *buf to a uin16_t because I think I have to use the whole accessable DR-Register, but come into the "HardFault_Handler" and had to reset.

Does anybody know how I can get the whole 16bits data?

Thanks, Tim

Re: Lpc1796 ssp/ssi

lpcware — Thu, 16 Jun 2016 02:53:43 GMT

Content originally posted in LPCWare by Ex-Zero on Thu Jan 26 16:49:03 MST 2012
What's your DSS value?

Re: Lpc1796 ssp/ssi

lpcware — Thu, 16 Jun 2016 02:53:43 GMT

Content originally posted in LPCWare by timer on Thu Jan 26 23:53:14 MST 2012
Hi Zero,

the DSS is set to 1111 for 16-bit.
I could try to put it on 8-bit and change Lenght = 2.

Now I have now know time to test it, but, could this work?

Re: Lpc1796 ssp/ssi

lpcware — Thu, 16 Jun 2016 02:53:44 GMT

Content originally posted in LPCWare by Ex-Zero on Fri Jan 27 00:32:17 MST 2012
I'm not sure what your sensor is expecting

Of course chip select is always an issue, but if you switch off SSEL function and use CS via GPIO it could be possible that 2*8bit is working.
Otherwise you have to extend your SSP receive function to receive 16 bit :eek:

If your data register (LPC_SSP1->DR) is already able to receive correct 16 bit data you could also store them as 2 bytes in your byte buffer with something like:

*buf++ = (LPC_SSP1->DR>>8) & 0x0FF; //store byte 1
*buf++ = (LPC_SSP1->DR) & 0x0FF;    //store byte 2

Re: Lpc1796 ssp/ssi

lpcware — Thu, 16 Jun 2016 02:53:44 GMT

Content originally posted in LPCWare by timer on Fri Jan 27 05:26:13 MST 2012
Thanks,

with two times 8-bit I get good looking data. But they are shifted one bit so the first bit should be the even parity, but it don't look like :(

This is the datasheet from the IC in the Sensor: Datasheet

Re: Lpc1796 ssp/ssi

lpcware — Thu, 16 Jun 2016 02:53:45 GMT

Content originally posted in LPCWare by timer on Fri Jan 27 09:55:39 MST 2012
I found a way that it works.
Now I use 3 times 6-bit and get all my needed bits out of them.

Thank you for your help :)