SPI Slave using PIC24FJ64GP202 - c

Question

I have trouble with a PIC24FJ64GP202 to work as an spi slave.
I have simplified the code to the minimum possible in order to find the problem.
In this simple code, an spi master (it is an ATSAMD51N19A) will send 0x55 to a spi slave (it is a PIC24FJ64GP202) once per second at 1MHz.
I can see the signal waveforms on the slave pins so the transmission is fine (please see the attached image but please note that the sample code does not implement the spi2 that communicates with the GLCD because this part of the code works fine and I want to target the problem: making it work as a slave SPI to enventually receive commands from another microcontroller).
The problem is with the spi slave. I can confirm that the pins receives the signal (CSn, spi1 clk, SDI but when I debug the code, the spi interrupt will not fire with the PIC24FJ64GP202 that is configured in slave mode.
Here is the pinout for the spi slave (PIC24FJ64GP202):
CSn (SS): RB2, pin 6
Spi1 clk: RB3, pin 7
SDI: RB4, pin 11
SDO: RB5, pin 14
Any idea why the interrupt will not fire and why the SPI1BUFL and SPI1BUFH are always 0 eventhough the master sends 0x55 with a 1MHz clk once per second ?
Here is the slave simplified code (in one main.c file):
// FSEC
#pragma config BWRP = OFF //Boot Segment Write-Protect bit->Boot Segment may be written
#pragma config BSS = DISABLED //Boot Segment Code-Protect Level bits->No Protection (other than BWRP)
#pragma config BSEN = OFF //Boot Segment Control bit->No Boot Segment
#pragma config GWRP = OFF //General Segment Write-Protect bit->General Segment may be written
#pragma config GSS = DISABLED //General Segment Code-Protect Level bits->No Protection (other than GWRP)
#pragma config CWRP = OFF //Configuration Segment Write-Protect bit->Configuration Segment may be written
#pragma config CSS = DISABLED //Configuration Segment Code-Protect Level bits->No Protection (other than CWRP)
#pragma config AIVTDIS = OFF //Alternate Interrupt Vector Table bit->Disabled AIVT
// FBSLIM
#pragma config BSLIM = 8191 //Boot Segment Flash Page Address Limit bits->8191
// FOSCSEL
#pragma config FNOSC = FRC //Oscillator Source Selection->FRC
#pragma config PLLMODE = PLL96DIV2 //PLL Mode Selection->96 MHz PLL. Oscillator input is divided by 2 (8 MHz input)
#pragma config IESO = OFF //Two-speed Oscillator Start-up Enable bit->Start up with user-selected oscillator source
// FOSC
#pragma config POSCMD = NONE //Primary Oscillator Mode Select bits->Primary Oscillator disabled
#pragma config OSCIOFCN = OFF //OSC2 Pin Function bit->OSC2 is clock output
#pragma config SOSCSEL = OFF //SOSC Selection Configuration bits->Digital (SCLKI) mode
#pragma config PLLSS = PLL_FRC //PLL Secondary Selection Configuration bit->PLL is fed by the on-chip Fast RC (FRC) oscillator
#pragma config IOL1WAY = ON //Peripheral pin select configuration bit->Allow only one reconfiguration
#pragma config FCKSM = CSECMD //Clock Switching Mode bits->Clock switching is enabled,Fail-safe Clock Monitor is disabled
// FWDT
#pragma config WDTPS = PS32768 //Watchdog Timer Postscaler bits->1:32768
#pragma config FWPSA = PR128 //Watchdog Timer Prescaler bit->1:128
#pragma config FWDTEN = OFF //Watchdog Timer Enable bits->WDT and SWDTEN disabled
#pragma config WINDIS = OFF //Watchdog Timer Window Enable bit->Watchdog Timer in Non-Window mode
#pragma config WDTWIN = WIN25 //Watchdog Timer Window Select bits->WDT Window is 25% of WDT period
#pragma config WDTCMX = WDTCLK //WDT MUX Source Select bits->WDT clock source is determined by the WDTCLK Configuration bits
#pragma config WDTCLK = LPRC //WDT Clock Source Select bits->WDT uses LPRC
// FPOR
#pragma config BOREN = ON //Brown Out Enable bit->Brown-out Reset is Enabled
#pragma config LPREGEN = OFF //Low power regulator control->Low Voltage and Low Power Regulator are not available
#pragma config LPBOREN = ENABLE //Downside Voltage Protection Enable bit->Low Power BOR is enabled and active when main BOR is inactive
// FICD
#pragma config ICS = PGD1 //ICD Communication Channel Select bits->Communicate on PGEC1 and PGED1
#pragma config JTAGEN = OFF //JTAG Enable bit->JTAG is disabled
// FDMTIVTL
#pragma config DMTIVTL = 0 //Deadman Timer Interval Low Word->0
// FDMTIVTH
#pragma config DMTIVTH = 0 //Deadman Timer Interval High Word->0
// FDMTCNTL
#pragma config DMTCNTL = 0 //Deadman Timer Instruction Count Low Word->0
// FDMTCNTH
#pragma config DMTCNTH = 0 //Deadman Timer Instruction Count High Word->0
// FMDT
#pragma config DMTDIS = OFF //Deadman Timer Enable Bit->Dead Man Timer is Disabled and can be enabled by software
// FDEVOPT1
#pragma config ALTCMP1 = DISABLE //Alternate Comparator 1 Input Enable bit->C1INC is on RB13 and C3INC is on RA0
#pragma config TMPRPIN = OFF //Tamper Pin Enable bit->TMPRN pin function is disabled
#pragma config SOSCHP = ON //SOSC High Power Enable bit (valid only when SOSCSEL = 1->Enable SOSC high power mode (default)
#pragma config ALTI2C1 = ALTI2C1_OFF //Alternate I2C pin Location->I2C1 Pin mapped to SDA1/SCL1 pins
#pragma config ALTCMP2 = DISABLE //Alternate Comparator 2 Input Enable bit->C2INC is on RA4 and C2IND is on RB4
#pragma config SMB3EN = SMBUS3 //SM Bus Enable->SMBus 3.0 input levels
#ifndef FCY
#define FCY 16000000UL
#endif
#include <xc.h>
#include <libpic30.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
static void CLK_Initialize(void);
static void PPS_Initialize(void);
static void PORT_Initialize(void);
static void SPI1_Initialize(void);
static void INTERRUPT_Initialize(void);
static uint8_t SPI1_exchangeByte(uint8_t data);
static void MSSP1_InterruptHandler(void);
volatile uint8_t sPI_receivedData = 0; /* Data that will be received on the spi bus of the slave */
volatile uint8_t writeData = 1; /* Data that will be transmitted (don't care) */
#define SPI_SS_TRIS TRISBbits.TRISB2
#define SPI_SS_PORT PORTBbits.RB2
#define lcdBackLight_RA2_SetHigh() (_LATA2 = 1)
#define lcdBackLight_RA2_SetLow() (_LATA2 = 0)
#define lcdBackLight_RA2_Toggle() (_LATA2 ^= 1)
#define status0_LED_SetHigh() (_LATB7 = 1)
#define status0_LED_SetLow() (_LATB7 = 0)
#define status0_LED_Toggle() (_LATB7 ^= 1)
#define lcd_FrontPanel_CSn_SetHigh() (_LATB2 = 1)
#define lcd_FrontPanel_CSn_SetLow() (_LATB2 = 0)
#define lcd_FrontPanel_CSn_Toggle() (_LATB2 ^= 1)
#define lcd_FrontPanel_CSn_GetValue() _RB2
#define spi1clk1_GetValue() _RB3
#define spi1SI_GetValue() _RB4
#define status0_SetHigh() (_LATB7 = 1)
#define status0_SetLow() (_LATB7 = 0)
#define status0_Toggle() (_LATB7 ^= 1)
static void CLK_Initialize(void)
{
// CPDIV 1:1; PLLEN disabled; DOZE 1:8; RCDIV FRC; DOZEN disabled; ROI disabled;
CLKDIV = 0x3000;
// STOR disabled; STORPOL Interrupt when STOR is 1; STSIDL disabled; STLPOL Interrupt when STLOCK is 1; STLOCK disabled; STSRC SOSC; STEN disabled; TUN Center frequency;
OSCTUN = 0x00;
// ROEN disabled; ROSWEN disabled; ROSEL FOSC; ROOUT disabled; ROSIDL disabled; ROSLP disabled;
REFOCONL = 0x00;
// RODIV 0;
REFOCONH = 0x00;
// DIV 0;
OSCDIV = 0x00;
// TRIM 0;
OSCFDIV = 0x00;
// AD1MD enabled; T3MD enabled; T1MD enabled; U2MD enabled; T2MD enabled; U1MD enabled; SPI2MD enabled; SPI1MD enabled; I2C1MD enabled;
PMD1 = 0x00;
// RTCCMD enabled; CMPMD enabled; CRCMD enabled; I2C2MD enabled;
PMD3 = 0x00;
// REFOMD enabled; HLVDMD enabled;
PMD4 = 0x00;
// CCP2MD enabled; CCP1MD enabled; CCP4MD enabled; CCP3MD enabled; CCP5MD enabled;
PMD5 = 0x00;
// DMA0MD enabled;
PMD7 = 0x00;
// DMTMD enabled; CLC3MD enabled; CLC4MD enabled; CLC1MD enabled; CLC2MD enabled;
PMD8 = 0x00;
// CF no clock failure; NOSC FRCPLL; SOSCEN disabled; POSCEN disabled; CLKLOCK unlocked; OSWEN Switch is Complete; IOLOCK not-active;
__builtin_write_OSCCONH((uint8_t) (0x01));
__builtin_write_OSCCONL((uint8_t) (0x01));
// Wait for Clock switch to occur
while (OSCCONbits.OSWEN != 0);
while (OSCCONbits.LOCK != 1);
}
static void PPS_Initialize(void)
{
__builtin_write_OSCCONL(OSCCON & 0xbf); // unlock PPS
//SPI1 PPS configuration
RPINR21bits.SS1R = 0x0002; //RB2->SPI1:SSn
RPINR20bits.SCK1R = 0x0003; //RB3->SPI1:SCK1IN
RPINR20bits.SDI1R = 0x0004; //RB4->SPI1:SDI1
RPOR2bits.RP5R = 0x0007; //RB5->SPI1:SDO1
__builtin_write_OSCCONL(OSCCON | 0x40); // lock PPS
}
static void PORT_Initialize(void)
{
TRISAbits.TRISA2 = 0x0000;//lcd backlight
TRISBbits.TRISB7 = 0x0000;//status0
TRISBbits.TRISB5 = 0x0000;//spi1_MISO
TRISBbits.TRISB4 = 0x0001;//spi1_MOSI
TRISBbits.TRISB3 = 0x0001;//spi1_SCK
TRISBbits.TRISB2 = 0x0001;//lcd_FrontPanel_CSn
/****************************************************************************
* Setting the Analog/Digital Configuration SFR(s)
***************************************************************************/
ANSA = 0x0000;//all digital IO
ANSB = 0x0000;
}
static void SPI1_Initialize(void)
{
IEC0bits.SPI1IE = 0; // disable spi1 interrupt
//config SPI1
SPI1CON1bits.SPIEN = 0; // disable SPI port
SPI1BUFL = 0; // clear SPI buffer Low bits
SPI1BUFH = 0; // clear SPI buffer High bits
SPI1CON1Lbits.ENHBUF = 0; // Clear the ENHBUF bit (SPIxCON1L[0]) if using Standard Buffer mode
IFS0bits.SPI1IF = 0; // clear interrupt flag
// SPI1: SPI 1
// Priority: 1
IPC2bits.SPI1IP = 1; // interrupt priority set to the highest
IEC0bits.SPI1IE = 1; // enable spi1 interrupt
SPI_SS_PORT = 1; //
SPI_SS_TRIS = 1; // set SS as input
IFS0bits.SPI1IF = 0; // clear interrupt flag
IEC0bits.SPI1IE = 1; // enable spi1 interrupt
SPI1STATLbits.SPIROV = 0; // Clear the SPIROV bit
//desired settings
//Write the desired settings to the SPI1CON1L register with MSTEN (SPI1CON1L[5]) = 0.
SPI1CON1bits.MSTEN = 0; // 1 = Master mode; 0 = Slave mode
SPI1CON1Lbits.SPISIDL = 0; // Continue module operation in Idle mode
SPI1CON1bits.DISSDO = 0; // SDOx pin is controlled by the module
SPI1CON1bits.MODE16 = 0; // set in 16-bit mode, clear in 8-bit mode
SPI1CON1bits.SMP = 0; // SMP must be cleared when SPIx is used in Slave mode
SPI1CON1bits.CKP = 1; // CKP and CKE is subject to change ...
SPI1CON1bits.CKE = 0; // ... based on your communication mode.
SPI1CON1bits.SSEN = 1; // SSx pin is used for Slave mode
SPI1CON1Lbits.ENHBUF = 0;
//SPI1CON2 = 0; // non-framed mode
SPI1CON1bits.SPIEN = 1; // enable SPI port, clear status
}
static void INTERRUPT_Initialize(void)
{
INTCON2bits.GIE = 1; /* Enable Global Interrupts */
}
uint32_t gCounter;
int main(void)
{
CLK_Initialize();
PPS_Initialize();
PORT_Initialize();
SPI1_Initialize();
INTERRUPT_Initialize();
gCounter = 0;
status0_LED_SetHigh();
while(1)
{
//just to watch CSn signal coming once per second on the spi slave bus
if(!lcd_FrontPanel_CSn_GetValue())//!cs_1 && clk_1)
{
status0_Toggle();
lcdBackLight_RA2_SetHigh();
gCounter++;
__delay_ms(100);
}
else //if(!cs_1)
{
lcdBackLight_RA2_SetLow();
}
if(sPI_receivedData > 1)
status0_Toggle();
}
}
static uint8_t SPI1_exchangeByte(uint8_t data)
{
SPI1BUFL = data;
while(!IFS0bits.SPI1IF) /* Wait until data is exchanged */
{
;
}
IFS0bits.SPI1IF = 0;
return SPI1BUFL;
}
static void MSSP1_InterruptHandler(void)
{
sPI_receivedData = SPI1_exchangeByte(writeData);
}
//spi1 interrupt never fired. Why? ...SPI1 pins are receiving the data and the clk once per second but interrupt will not fire... Why?
void __attribute__((__interrupt__,__auto_psv__)) _SPI1Interrupt(void)//void __attribute__ (( interrupt, no_auto_psv )) _SPI1Interrupt ( void ) //void __interrupt() INTERRUPT_InterruptManager(void)
{
if(IEC0bits.SPI1IE == 1 && IFS0bits.SPI1IF == 1)
{
MSSP1_InterruptHandler();
}
}

Answer 1

Did not find why the spi slave configuration doesnt work with the PIC24FJ64GP202. We did try a development board Explorer 16 with a PIC24FJ128GA010 and the SPI slave works perfectly with the same above code (except the pinout).
... Still dont know why the PIC24FJ64GP202 gives this issue...
So,
To save the hardware we have for our product, it was possible to switch and use the spi CS pin as an Rx UART instead. The uart works perfectly for our requirements... We were lucky to have that pin configurable in UART on both the ATSAMD51N19 in TX and the PIC24F64GP202 in RX.