PIC24FJ64GA002, PPS for SPI

[Drirr]

Hi

I just switched to the PIC24F series. After reading the datasheet, I noticed that I need to set up the PPS (Peripheral Pin Select) to make SPI work.

I'm using the PIC24FJ64GA002 in a 28-Pin SPDIP package.

On page 41 of the PIC24FJ64GA002 datasheet, there is a PPS table. I believe that these lines represent registers where I can select what is connected to RPx. For example, does "RPINR20.SDIR0 = 6" connect SDI to RP6? Are the other bits, SDIR1 and SDIR2, for connecting the same SDI to other ports? Does anyone have a functional configuration for the SPI PPS pins? Where exactly in this table can I find all the SPI1 module inputs and outputs? Do I need to set the TRIS register for PPS?

Thanks, David

[voltsandjolts]

e.g.

https://github.com/vintagechips/ttbasic_pic24f/blob/5b3b0f14fa33c5dc2573bff9ad8bf15fa5fe9897/ttbasic.X/sci.c#L16

[Drirr]

@voltsandjolts, thanks for the reply.

TRISBbits.TRISB10 = 0; // TX
TRISBbits.TRISB11 = 1; // RX

I see that I need to set the TRIS register.

RPOR5bits.RP10R = 5; // 5 = U2TX

I understand that U2TX is mapped to PGED2/TDI/RP10/CN16/PMD2/RB10, but why did he use "5"?

RPINR19bits.U2RXR = 11; // 11 = RP11

I understand that U2RXR is mapped to RP11.

[voltsandjolts]

Probably best to read the datasheet, section 10.4 PPS

[Drirr]

By bad, overlook table 10-3. 

RPOR4bits.RP8R = 7;      // RP8 as SDO1
RPOR3bits.RP7R = 8;      // RP7 as SCK1

Thanks!

[newtekuser]

I was in a similar boat a few days ago when I transitioned my project from PIC16F to PIC18F, but as I later found I didn't have to set PPS to get I2C or EUSART to work. So I wonder is setting PPS only necessary for some protocols or some devices such as your PIC24?
Or is configuring PPS only necessary if you want to remap these peripherals to different ports other than the default ones? The behavior on mine seems to point to the latter in my case.

[Drirr]

@newtekuser
I believe that for the PIC24FJ64GA002, peripheral mapping is necessary. I tried testing SPI without using PPS but had no success. Maybe someone with more experience could advise?

[DavidAlfa]

Yes, PIC24 connects most peripherals (If not all) through the PPS.
It's an engineering marvel, connect any pin to any peripheral!

PIC18s don't have PPS, or at least didn't, maybe newer ones do.

[newtekuser]

Yes, PIC24 connects most peripherals (If not all) through the PPS.
It's an engineering marvel, connect any pin to any peripheral!

PIC18s don't have PPS, or at least didn't, maybe newer ones do.

The PIC18F46K40 I’m using does have PPS.

[mikeselectricstuff]

Some (all?) PPS units have defaults that route functions to particular pins without setting up explicitly - typically shown in the page after the pinout diagrams

[DavidAlfa]

AFAIK, not the case, enabling SPI without configuring PPS doesn't set any default pins, see attached pic.
I recall some special peripherals not using it, perhabs I2C?

[mikeselectricstuff]

AFAIK, not the case, enabling SPI without configuring PPS doesn't set any default pins, see attached pic.
I recall some special peripherals not using it, perhabs I2C?

(Attachment Link)

Varies by family - it's a while since I used PIC24 but I think the PIC16F15xx have default PPS settings

[mikeselectricstuff]

AFAIK, not the case, enabling SPI without configuring PPS doesn't set any default pins, see attached pic.
I recall some special peripherals not using it, perhabs I2C?

(Attachment Link)

PPS functionality does vary quite a lot by family
I think I2C is the only non-PPS peripheral on PIC24. On PIC16F15xxx, I2C can be changes with PPS but there are some constraints on signal levels if using alternate pins.

[voltsandjolts]

https://developerhelp.microchip.com/xwiki/bin/view/products/mcu-mpu/8bit-pic/peripherals/pin-select/

Some Microchip customers may be familiar with PPS from the PIC24 product line. PPS for the 8-bit family differs in that each digital peripheral input signal is connected to a pin by default. This stands in contrast to PPS for the PIC24 products, where peripherals are left unconnected by default. For 8-bit PPS, peripheral input and output signals need to be selected before the peripheral is enabled. Then the peripheral should be enabled after both input and output selections have been completed.

[DavidAlfa]

PIC16F18xxx came much later, yes, they have a default PPS assignment on reset.
PIC24 and dsPIC33 are way different in this matter.

[NorthGuy]

I2C requires different voltage levels and open drain outputs, so it often has dedicated pins.

It is all improving with time. Newer PICs have better PPS, regardless of family.