TMS570LS0914: Facing issue with Duty and period reading with HET instruction set

Usha,

Thanks for reaching out to the E2E.  I need to get this re-assigned to the correct engineer in the team.  Please give us another day to respond to your question.

Best,

Matthew

Hi Usha Kumari,

We have one internal AI which can analyze all the relevant documents of this device, i got couple of suggestions from it. So, i suggesting you refer these suggestions once and if this is not helpful then i will try to debug further on your issue.

Root Cause Analysis

The issue appears to be in the capture mechanism of the N2HET module. Looking at your instruction set:

1. Instruction 25 is a PCNT instruction configured to capture duty cycle
2. Instruction 26 is a PCNT instruction configured to capture period

The PCNT instructions are designed to measure active pulses. When:

• Duty cycle is 0%: There are no rising edges to trigger the capture
• Duty cycle is 100%: There are no falling edges to trigger the capture
• Signal is off: No transitions occur to update the capture values

Recommended Solutions

1. Implement a Timeout Detection Mechanism

void capGetSignal(hetRAMBASE_t* hetRAM, uint32 cap, hetSIGNAL_t* signal)  
{  
    static uint32 lastPwmData = 0;
    static uint32 noUpdateCounter = 0;
    
    uint32 currentPwmData = hetRAM->Instruction[(cap << 1U) + 25U].Data;
    uint32 pwmDuty = currentPwmData >> 7U;  
    uint32 pwmPeriod = (hetRAM->Instruction[(cap << 1U) + 26U].Data) >> 7U;
    
    // Check if data has been updated
    if (currentPwmData == lastPwmData) {
        noUpdateCounter++;
        if (noUpdateCounter > TIMEOUT_THRESHOLD) {
            // No updates for too long - assume signal is off or at 0/100% duty
            signal->duty = 0; // Or determine if it should be 100 based on pin state
            signal->period = 0;
            return;
        }
    } else {
        noUpdateCounter = 0;
        lastPwmData = currentPwmData;
    }
    
    signal->duty = (pwmDuty * 100U) / pwmPeriod;
    
    if (hetRAM == hetRAM1) {  
        signal->period = ((float64)pwmPeriod * 1066.667F) / 1000.0F;  
    } else {  
        signal->period = ((float64)pwmPeriod * 1066.667F) / 1000.0F;  
    }  
}

2. Use Additional HET Instructions for Edge Detection

Modify your HET program to include edge detection instructions that can identify when the signal is static at high or low levels.

3. Add Pin State Monitoring

void capGetSignal(hetRAMBASE_t* hetRAM, uint32 cap, hetSIGNAL_t* signal)  
{  
    uint32 pwmDuty = (hetRAM->Instruction[(cap << 1U) + 25U].Data) >> 7U;  
    uint32 pwmPeriod = (hetRAM->Instruction[(cap << 1U) + 26U].Data) >> 7U;
    
    // Check pin state directly
    uint32 pinState = (gioGetBit(hetPORT1, cap) == 1);
    
    // If period hasn't changed for X cycles and pin is consistently high/low
    if (isSignalStatic(pwmPeriod)) {
        signal->duty = pinState ? 100 : 0;
        signal->period = 0;  // Or maintain last valid period
        return;
    }
    
    signal->duty = (pwmDuty * 100U) / pwmPeriod;
    
    if (hetRAM == hetRAM1) {  
        signal->period = ((float64)pwmPeriod * 1066.667F) / 1000.0F;  
    } else {  
        signal->period = ((float64)pwmPeriod * 1066.667F) / 1000.0F;  
    }  
}

4. Use a Different Capture Configuration

Consider modifying your HET instructions to use edge-triggered interrupts that can detect both the presence and absence of transitions within an expected timeframe.

--
Thanks & regards,
Jagadish.