DLP3021-Q1: The issue of reading initial values from T451/411 using FPGA.

Hi Johns,

Welcome to the E2E forum and thank you for your interest in DLP® technology.

Our team is discussing this behavior for the FPGA temperature read. How long does it typically take for the correct temperature to be returned?

Regards,

Austin

Dear Austin,

It takes approximately 15 to 20s for the temperature to reach the actual value.

Regards,

Johns

Hello Johns,

Thank you for the information!

Please all me some time to investigate this behavior.

Can you say you own the TI EVM or custom board?

Regards,

Lori 

Hi Lori

Thank you for your invaluable assistance.

Yes, I have the 3021 EVM.

Regards,

Johns

Hi Johns,

How did you test the EVM under the ambient temperature is above 70 degrees Celsius? Did you place the EVM in a temperature chamber? 

Are you able to use a IR temperature gun or thermocouple to test the temperature on TMP411 and read back the temperature local channel for TMP, then compare the difference? 

I was able to test on a TI EVM, and I could see the Temperature Local channel value changed quickly to reach a high temp.

Regards,

Lori 

Hi Lori,

Initially, we were using our own designed board and placing it in the oven with a thermocouple attached to the TMP451 to record the actual temperature. The MCU would then send the command 0x9C every 10ms to read the FPGA values. However, we noticed that regardless of the oven temperature, the initial value of 0x9C was always 1424(25°C), and it took about 15s to reach the actual ambient temperature.

Therefore, we also placed the 3021 EVM in the oven and set it to a static temperature of 70°C for 2 hrs. Then, we powered it on and used the DLP Control Program to read the local values. However, we still observed that the initial temperature always started from 25°C, and it took approximately 15s to read a value close to 70°C.

Could you please clarify how fast you mean by "rapid changes"? How much time does it typically take for the local readings to go from 25°C to the actual temperature?

Thank you for your assistance.

Best regards,

Johns

Hi Johns,

Do you have another system you can test to see if the TMP Local temperature reading need to take `15s to reach the actual temperature?

What's the FPGA version you are using? How do you convert the temperature reading from 1424(25°C)? 

I don't see the startup TMP Local temp read as 1424(25°C) on a TI EVM.

Regards,

Lori 

Hi Lori

Please refer to the attached image, which shows the local (0x9C) value requested by the MCU after 650ms of power-on, as recorded by the logic analyzer. It reads as 0x05 0x90 = 1424 = 25°C, correct? (initial ambient temperature 60°C)

The value is 0x07 0x18 = 1816 = 49.5°C in 5s.

The value is 0x07 0x99 = 1945 = 57.5625°C in 10s.

The value is 0x07 0xD7 = 2007 = 61.43°C in 15s.

Is such variation normal?

Is the FPGA version referring to this?

Hi Johns,

Thanks for the input.

Are you able to read the TMP local temp through Control Program?

I convert the temp reading as 1600 = 0x640 = 100F.

If I keep the EVM running for a few minutes and power cycle the EVM, I can see the the initial value of TMP local temp changed. 

Regards,

Lori 

Hi Lori,

Yes, I can use the DLP Control Program to read the Local Temp, but even at an ambient temperature of 70 degrees, the initial reading is always 1424 before changing to 1600.

Due to the nature of our product, it may not be possible to calibrate the initial local temp as you suggested by performing multiple restarts.

Could you please help me clarify a few points that I can communicate to my supervisor/client?

1. Can you confirm if the FPGA also returns 1424 initially on your end?
2. How many milliseconds does it take to get an accurate temperature reading above 50 degrees ambient temperature? (Do you have any recommended timing?)
3. Are there any plans for future FPGA firmware updates?

Thank you for your assistance.

Best regards,

Johns

Hi Johns,

1. I don't see the 0x9C command returns 1424 every time as initial value on my end. 

2. Currently, I have limited access to test the EVM in a temperature chamber and measure the time. I may need to work with the team to see how we can support here.

3. I don't aware that we have FPGA firmware update plan on DLP3021-Q1.

Regards,

Lori 

Hi Lori,

I have recorded the changes every second from 0 to 10 seconds and every 5 seconds from 0 to 60 seconds. Please find the attached data.

Initially, the raw values seem to quickly reach the ambient temperature, but as time progresses, they gradually deviate from the actual temperature. However, the trend of the filtered values clearly shows a deviation from the actual temperature.

Would it be possible for you to conduct a similar experiment on your end? It would involve allowing the EVM to stabilize at an ambient temperature above 50 degrees for 30 minutes to 1 hour, and then reading the value of 0x9C using the MCU every 1 second after startup, while recording the changes in 10-second intervals.

Thank you for your assistance.

Best regards,

Johns

Hi Johns,

Thank you for the data. We will continue to look into this issue and attempt to replicate and conduct the experiment but this may take some time. There is a USA holiday part of next week so please expect a delayed response.

Thanks,

Alex Chan