LPC1778 - INPUT INVERSION ON SSP0_SSEL P1[21]

[lpcware]

Content originally posted in LPCWare by wwwenrico on Thu Sep 17 03:58:20 MST 2015
Hi,

I'm designing a board based on the LPC1778 microcontroller.

I have to interface the LPC1778 to an external module that acts as an SSP master.

I'll configure the SSP0 interface as a slave.


The SSEL signal of the master is inverted with respect to the standard.
In fact, the idle state is 0 Volt and not 3.3 Volt.


QUESTION:
Can I use the IOCON_P1_21 register to invert the input signal and have the SSEL inverted?


Best Regards,
Enrico Migliore

[lpcware]

Content originally posted in LPCWare by starblue on Sat Sep 26 07:35:17 MST 2015
That sounds a bit contorted.
Why don't you drive the chip select from software anyway?

[lpcware]

Content originally posted in LPCWare by wwwenrico on Thu Sep 24 07:03:44 MST 2015
Hi,

I might also use 2 pins of the microcontroller and build a software inverter interrupt driven.


Best Regards,
Enrico Migliore

[lpcware]

Content originally posted in LPCWare by wwwenrico on Mon Sep 21 07:11:27 MST 2015
Hi,

yes, I'll do that.

Best Regards,
Enrico Migliore

[lpcware]

Content originally posted in LPCWare by MikeSimmonds on Fri Sep 18 09:07:38 MST 2015
Why not leave the not gate footprint on the PCB and just bridge input to output with a link wire just in case?

[lpcware]

Content originally posted in LPCWare by wwwenrico on Thu Sep 17 20:10:43 MST 2015
Hi DF9DW,

thank you for your answer.

Are you 100% sure about that?

I'm removing the NOT gate from the schematics and I would like to be completely sure that I won't have to redesign the PCB.

Best Regards,
Enrico Migliore

[lpcware]

Content originally posted in LPCWare by DF9DQ on Thu Sep 17 12:04:04 MST 2015
This will work. The inverter option in the IOCON registers also works on the special functions like SSEL.