FlexIO timer trigger

[Fanta]

Hi,

I'm trying to make use of FlexIO module on S32K358. My application is not a standard communication protocal, so the components in RTD driver cannot help me out. I have to write the registers directly.

Specifically, I am using 3pins, 1 shifter and 1 timer in FlexIO.  Ideally, trigger signal rising edge on pin1 triggers  the timer, and then timer outputs clk signal on pin2 to acquire data, at the same time generates the shift clock for the shifter. Shifter read the data from pin0. Eventually,  the data frame is read from shifterbuf, when eMIOS interrupt is triggered by trigger signal falling edge. The pin configuration is as followed.

The question is, I cannot even see the FlexIO output clk signal on pin2 on the oscilloscope. I am pretty sure the the clock and pin initialazation is correct, and trigger signal exists,  because it also tirggers eMIOS interrupt and that works fine. What might go wrong? The FlexIO configuration is as followed.

#include "S32K358_FLEXIO.h"

Clock_Ip_Init(&Clock_Ip_aClockConfig[0]);

Siul2_Port_Ip_Init(NUM_OF_CONFIGURED_PINS_PortContainer_0_BOARD_InitPeripherals, g_pin_mux_InitConfigArr_PortContainer_0_BOARD_InitPeripherals);

IP_FLEXIO->CTRL = (uint32)1u; //enable FlexIO

IP_FLEXIO->SHIFTCFG[0] = FLEXIO_SHIFTCFG_PWIDTH(0) | //1 bit shift
FLEXIO_SHIFTCFG_SSIZE(0) | //32bit shift register
FLEXIO_SHIFTCFG_LATST(0) | //store the pre-shift register state
FLEXIO_SHIFTCFG_INSRC(0) |//pin input
FLEXIO_SHIFTCFG_SSTOP(0) |//disable stop bit
FLEXIO_SHIFTCFG_SSTART(0); //disable start bit

IP_FLEXIO->SHIFTCTL[0] = FLEXIO_SHIFTCTL_TIMSEL(0) | //timer0 generate the shift clock
FLEXIO_SHIFTCTL_TIMPOL(1) | //shift occurs on the negative edge
FLEXIO_SHIFTCTL_PINCFG(0) | //shifter pin output disabled
FLEXIO_SHIFTCTL_PINSEL(0) | //select FXIO_D0 as shifter input.
FLEXIO_SHIFTCTL_PINPOL(0) | //shifter pin active high
FLEXIO_SHIFTCTL_SMOD(1); //receive mode

IP_FLEXIO->TIMCMP[0] = 0x00007951; //8 bit baud rate mode
// 16 bit for 1 data frame, 5MHz baudrate (160MHz for FlexIO_clk)
//TIMCMP[7:0]=15 baudrate divider/2 - 1
//TIMCMP[15:8]=31 bits*2-1

IP_FLEXIO->TIMCFG[0] = FLEXIO_TIMCFG_TIMOUT(3) | //Logic zero when enabled and on timer reset
FLEXIO_TIMCFG_TIMDEC(0) | //Decrement counter on FLEXIO clock; shift clock equals timer output
FLEXIO_TIMCFG_TIMRST(6) | //Timer reset on trigger rising edge
FLEXIO_TIMCFG_TIMDIS(6) | //Timer disabled on trigger falling edge
FLEXIO_TIMCFG_TIMENA(6) |//Timer enabled on trigger rising edge
FLEXIO_TIMCFG_TSTOP(0) | //disable stop bit
FLEXIO_TIMCFG_TSTART(0); //disable start bit

IP_FLEXIO->TIMCTL[0] = FLEXIO_TIMCTL_TRGSEL(2) | //select FXIO_D1 as internal trigger
FLEXIO_TIMCTL_TRGPOL(0) | //trigger active high
FLEXIO_TIMCTL_TRGSRC(1) | //internal trigger
FLEXIO_TIMCTL_PINCFG(3) | //timer pin output
FLEXIO_TIMCTL_PINSEL(2) | //select FXIO_D2 as timer pin
FLEXIO_TIMCTL_PINPOL(0) | //timer pin active high
FLEXIO_TIMCTL_PININS(0) | //PINSEL selects pin input and output
FLEXIO_TIMCTL_ONETIM(0) | //Generate the timer enable event as normal
FLEXIO_TIMCTL_TIMOD(1); //8-bit baud counter mode

Thanks

S32K3 

[danielmartynek]

Hi @Fanta,

Can you just confirm there is no issue with the HW by toggling D2:

// Enable output on pin D2
IP_FLEXIO->PINOUTE |= (1 << 2);

// Toggle pin D2
IP_FLEXIO->PINOUTTOG = (1 << 2);

// Toggle pin D2
IP_FLEXIO->PINOUTTOG = (1 << 2);

Can you maybe share the whole project, so that I can check the clock, etc?

Thank you,

BR, Daniel

[Fanta]

Hi @danielmartynek,
Excuse me, I have kept trying these days but still no clue, do you have any?

Thanks

[danielmartynek · Accepted solution]

Hi @Fanta,

EDITED:

I’m experiencing issues with reliably outputting the baud rate. The behavior is inconsistent.

Interestingly, the exact same code runs without any modification on the S32K344 and works as expected.

However, on the S23K358 MCU:

When I disconnect the debugger and power cycle the MCU, I do get the baud rate output on pin D2 (PTF8).
Also, when the FLEXIO_CTRL[DBGE] bit is set, the baud rate seems to be working as well.
Could you please test this behavior?

Before doing so, check the status of the FlexIO_PIN[1] register while toggling the trigger on D1, to be sure the FlexIO sees the trigger.

Thank you,

BR, Daniel

[Fanta]

Hi @danielmartynek ,
You are right, I disconnected the debugger and re-powered the MCU, and got the expected result. Thanks a lot.
Indeed it is an interesting problem, don't know what exactly goes wrong, the MCU chip or evulation board. My EVB is S32K3X8EVB-Q289, SCH-54870 REV C, 700-54780 REV A. I might design a board using S32K358 in future, and keep tracking this issue. And hope NXP can put some resource on this issue.

[danielmartynek]

HI @Fanta,

It seems to a problem of all multicore S32K3xx MCUs.

If one core is halted by the debugger, the MCU is in active debug mode.

The FlexIO module does not work in this mode unless FLEXIO_CTRL[DBGE] is set.

Regards,

Daniel

[Fanta]

Hi @danielmartynek ,

I have tried toggling D2 as your suggestion, and confirmed that there is no issue with my HW. And here is the whole project, running at S32DS 3.5 and SDK 5.0.0 .

Thanks

[danielmartynek]

Hi @Fanta,

Let me test it on my side.

How does this protocol differ from SPI?

BR, Daniel

[Fanta]

Thanks. And yes, to some degree it is an SPI, but without CS and MOSI. I would like to save some resource on FlexIO for another applications, so I directly write FlexIO registers rather than use FlexIO SPI RTD driver.