Hallo,
i have the following problem to solve:
an interrupt should be triggered when the frame-signal of a
SPI-interface changes from 0 to 1. If, at the time of enabling this
interrupt, the frame-signal is already high, the interrupt should be
triggered by software instead of the rising edge.
I am using int-structures representing the register-bits of EXTI and
other peripherals mapped to the according places within the
bit-banding-area of the micro. These are name XXXbbbits. I am also using
bit-structures which are representing the structures of their according
registers to manipulate two or more bits at a time. Those are called
XXXbits and are mapped to the registers original locations.
My SPI acts as a Slave.
I tried the following:
1 | #define TDXSPIClearFrameInt() EXTIbbbits.PR.PR4=EXTI_PR_INT_CLR
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2 | #define TDXSPIDisableFrameInt() EXTIbbbits.IMR.MR4=EXTI_IMR_INT_DIS
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3 | #define TDXSPIEnableFrameInt() EXTIbbbits.IMR.MR4=EXTI_IMR_INT_EN
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4 | #define TDXSPIClearPendingFrameInt() NVIC_ClearPendingIRQ(EXTI4_IRQn)
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5 | #define TDXSPISelectRisingFrameInt() EXTIbbbits.RTSR.TR4=EXTI_RTSR_RE_EN
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6 | #define TDXSPIUnselectRisingFrameInt() EXTIbbbits.RTSR.TR4=EXTI_RTSR_RE_DIS
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7 | #define TDXSPISelectFallingFrameInt() EXTIbbbits.FTSR.TR4=EXTI_FTSR_FE_EN
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8 | #define TDXSPIUnselectFallingFrameInt() EXTIbbbits.FTSR.TR4=EXTI_FTSR_FE_DIS
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9 | #define TDXSPICondRqFrameInt(cond) EXTIbbbits.SWIER.SWIER4=cond?EXTI_SWIER_INT_RQ:~EXTI_SWIER_INT_RQ
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10 | #define TDXSPIRequestFrameInt() EXTIbbbits.SWIER.SWIER4=EXTI_SWIER_INT_RQ
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11 |
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12 | #define EXTI_IMR_INT_DIS 0u
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13 | #define EXTI_IMR_INT_EN 1u
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14 | #define EXTI_EMR_EVT_DIS 0u
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15 | #define EXTI_EMR_EVT_EN 1u
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16 | #define EXTI_RTSR_RE_DIS 0u
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17 | #define EXTI_RTSR_RE_EN 1u
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18 | #define EXTI_FTSR_FE_DIS 0u
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19 | #define EXTI_FTSR_FE_EN 1u
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20 | #define EXTI_SWIER_INT_RQ 1u
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21 | #define EXTI_PR_INT_CLR 1u
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22 |
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23 |
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24 | void TDXSPISetTimeOut(enum eTDXSPITimeOutIntSources Source)
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25 | {
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26 | // Set time-out-value, enable interrupt for retrigger
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27 | // timer is not startet in case of RX or TX since we don't know when the TDX starts transmission
|
28 | // timer is started after reception of the first unit
|
29 | // timer-interrupt only used for checking FRAME-idle-time
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30 | // FRAME-interrupt is used to start timer in case of TX and FRAME supervision
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31 | // time-out occured when UIF-flag is set
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32 | TDXSPIDisableFrameInt(); // disable FRAME-interrrupts
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33 | TDXSPIUnselectRisingFrameInt(); // not sensitive to any edge
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34 | TDXSPIUnselectFallingFrameInt();
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35 | TDXSPIDisableTimerInt(); // disable timer-interruptss
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36 | TDXSPIStopTimer(); // stop timer
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37 | switch(Source)
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38 | {
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39 | case TDXSPITimeOutIntSource_SPIRX: // initialize timer to supervise time-out during reception
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40 | <some initialization>
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41 | break;
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42 |
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43 | case TDXSPITimeOutIntSource_SPITX: // initialize timer to supervise time-out during transmission
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44 | <some other initialization>
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45 | break;
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46 |
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47 | case TDXSPITimeOutIntSource_RDY: // initialize timer to supervise maximum response-time to RDY
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48 | <some other initialization>
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49 | break;
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50 |
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51 | case TDXSPITimeOutIntSource_FRAME: // initialize timer to supervise minimum idle-time of FRAME-signal
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52 | TDXSPITimerReloadReg=TDXSPIFRMMINIDLE;
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53 | TDXSPIUpdateTimer();
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54 | TDXSPIClearTimerStatus();
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55 | TDXSPIDEnableTimerInt(); // enable timer-INTs
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56 | TDXSPISelectRisingFrameInt(); // Rising edge interrupt only
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57 | TDXSPIClearFrameInt(); // clear pending INTs
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58 | TDXSPIClearPendingFrameInt();
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59 | if(TDXSPIFrameIsIdle()) // request Int manually if FRAME is already idle
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60 | {
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61 | TDXSPIRequestFrameInt();
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62 | }
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63 | TDXSPIEnableFrameInt(); // enable FRAME-INTs
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64 | break;
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Unfortunately, no interrupt is issued by software. The interrupt is
triggered only by hardware when the next positive edge occurs. But this
is one telegram to late.
If I exchange the last two commands, it runs ok:
1 | TDXSPIEnableFrameInt(); // enable FRAME-INTs
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2 | if(TDXSPIFrameIsIdle()) // request Int manually if FRAME is already idle
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3 | {
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4 | TDXSPIRequestFrameInt();
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5 | }
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But, I ran into a race-condition when FRAME has its positive edge while
the TDXSPIEnableFrameInt() is executed. In this case, the interrupt is
triggered twice, first by hardware, than again by the if-clause. This
should not happen.
I have no Idea, why the pending-bit is not set, when I use the first
example. The only way I found, was to disable the intrerrupts either
globally or in the NVIC, which I dislike both.
Has anybody a better idea or an explanation, why the first example
doesn't work?
Thanks in advance
Gernot
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