SPI slaveon DSPIC - embedded

Question

Working on DSPIC33FJ128MC804
The problem :
I am completely unable to configura the SPI as slave. SPI Interrupt does never fire. if(SPI2STATbits.SPIRBF || SPI2STATbits.SPIROV) is always evaluated as false too.
I tried
with SSEN enabled and disabled, and many other configurations...
The clock is present and generated by an Arduino Uno as master, the pin mapping has been checked 3 times. This device is not subject to the SPI slave CSn errata of this familly.
Does anyone see what I do wrong ? or have a working example as SLAVE ?
// Setup hardware I/Os configuration
SPI_SLAVE_CSN_TRIS = 1; //input
SPI_SLAVE_CLK_TRIS = 1;
SPI_SLAVE_MOSI_TRIS = 1;
SPI_SLAVE_MISO_TRIS = 0; //output
// Setup remapable pins
SPI_SLAVE_MISO_RPN = _RPOUT_SDO2; // configure RP output
RPINR22bits.SDI2R = SPI_SLAVE_MOSI_RP_NUMBER; //configure inputs
RPINR22bits.SCK2R = SPI_SLAVE_CLK_RP_NUMBER;
RPINR23bits.SS2R = SPI_SLAVE_CSN_RP_NUMBER;
IFS2bits.SPI2IF = 0; // Clear interrupt flag
IEC2bits.SPI2IE = 0; // Disable interrupt
// Baudrate configuration (unused in slave mode )
SPI2CON1bits.PPRE = 0b11; //TODO needed in slave mode ?
SPI2CON1bits.SPRE = 0b110;
SPI2CON1bits.DISSCK = 0; // Internal serial clock
SPI2CON1bits.DISSDO = 0; // SDOx is controlled by the module
SPI2CON1bits.MODE16 = 0; // 8 bit mode //TODO check if 16 bit fit's better
SPI2CON1bits.SMP = 0; // 0 when slave
SPI2CON1bits.CKE = 1; // Emits SDO on SCK falling edge (slave samples on rising)
SPI2CON1bits.CKP = 0; // SCK idle state is LOW level
SPI2CON1bits.SSEN = 1;// CSN pin used for slave mode
SPI2CON1bits.MSTEN = 0; // Slave mode is enabled
//SPI2CON2bits.SPIFSD = 1; //we are not in framed mode
SPI2STATbits.SPIEN = 1; // Enable SPI module
//TODO ISR priority
// Write the SPIx Interrupt Priority Control (SPIxIP) bits in the respective IPCx register to set the interrupt priority
SPI2BUF = 0xf3; // Clear data to be transmitted => for test
IFS2bits.SPI2IF = 0; // Clear interrupt flag
IEC2bits.SPI2IE = 1; // Enable interrupt
SOLVED
The RPN pin fucntions where locked in another part of the code I hadn't written.
I was not aware of this functionnality

Answer 1

I have no experience with SPI in slave mode but in general setting the priority of the interrupt on 16 and 32 bit pic MCUs are not optional, it must be set or the interrupt won't fire, at least that's been my experience. Set the IPCx bits relevant for the peripherals you use.
Try finding a code snippet where an interrupt function is defined and use that as a template. It's generally very similar for every peripheral. UART and maybe also the SPI module has a separate send and receive interrupt vector, both must be defined.
Somewhere in the main function, enable the interrupt and set the priority, at least non zero IIRC:
IEC0bits.AD1IE = 1; // Enable adc interrupt
IPC3bits.AD1IP = 4; // set priority above that of the serial port.
For an ADC I use this to define the interrupt. All you need to change is the _ADC1Interrupt part. See the datasheet and XC16 documentation for the correct function name.
// ADC1 interrupt vector
void __attribute__((__interrupt__(auto_psv))) _ADC1Interrupt(void)
{
if( IFS0bits.AD1IF ) // Check interrupt flag
{
}
IFS0bits.AD1IF = 0; // clear interrupt flag to prevent endless interrupts
}