The LPC21xx/LPC22xx's SPI. Am I missing something ?

Started by gregdeuerling July 12, 2004

Hello,

I have a Maxim thermocouple converter (MAX6675) hooked up to a
LPC2294's SPI. The MAX6675 is SPI read only device, i.e., enable
chip select and it starts shifting out bits on each SPI clock.

Is there no way to make the LPC's SPI receive a byte with out
sending a byte first ? I hate to have to bit bang the LPC's I/O's
to get the SPI functionality I need, but it looks like thats what
I'm going to have to do.

Am I over looking something ???



An Engineer's Guide to the LPC2100 Series


On Monday, July 12, 2004, at 11:52 AM, gregdeuerling wrote:

> I have a Maxim thermocouple converter (MAX6675) hooked up to a
> LPC2294's SPI. The MAX6675 is SPI read only device, i.e., enable
> chip select and it starts shifting out bits on each SPI clock.
>
> Is there no way to make the LPC's SPI receive a byte with out
> sending a byte first ? I hate to have to bit bang the LPC's I/O's
> to get the SPI functionality I need, but it looks like thats what
> I'm going to have to do.
>
> Am I over looking something ???
>

That's the way SPI works - a byte is received as it sent (as each bit
is clocked out, a bit is clocked in). You write a byte to the transmit
register, it sends/receives, then you read the transmit register to get
the byte back.

Just send a 0 (or whatever) in order to read.

Shannon