IWR1642: Question about HW trigger

Hi Chris,

First, please make sure there are no other signal on your Sync_in line.
For example with the DCA1000 connected you have to remove a 0Ohm resistor.
Otherwise signal jitter could cause errors while triggering.
AWR: www.tij.co.jp/.../tidrqr8.pdf

IWR BOM, Schematic, Assembly: http://www.ti.com/lit/zip/sprr256

Next check your Sync_in signal.
For the specific timing regulations an employee more familiar has to provide these infos.
I am using a PWM signal.
The rising edge starts the frame and is high for more than frame duration.
The next rising edge triggers the next frame. And so on.
This might depend on your silicon release.

I suggest for your customer to provide more info on pulse width and try different on- durations.

Regards,
Robert

Robert,

Customer is testing on their own board. And customer is ok to use external pulse signal input to SYNC_IN to trigger the frame start with HW trigger enabled. So I think there is no issue on their HW side.

Now customer found if they input a high level signal to SYNC_IN with HW trigger enabled, it will also trigger the frame start multi times. This is not as customer expected.

So the question is :
How to avoid mutli trigger (frame start) with high level signal inputs to SYNC_IN when HW trigger is enabled?

There are some details about the experiment:
We use the Oscilloscope to observe the SYNC_IN level, there are no other signal on Sync_in line.
the frame duration is 23ms,and the rising edge period is 25ms.when we input the rising edge,the frame will work in 25ms.when we use continuous input high level，the frame will work in 23ms period。

Hello,

  For the Sync_in pin as a hardware trigger customers need to follow below timing requirements.

Thanks and regards,

CHETHAN KUMAR Y.B.

Chethan,

Thanks a lot for your detail info on HW trigger!

The reason we asked this questions is because on customer's board, the SYNC_IN pin is connected to a RS485 output, which outputs high level by default when there is no signal input to RS485 chip.  So the default high level to SYNC_IN will trigger the frame start when HW trigger is enabled. And this is not what customer wants.

Do you have any idea to fix this issue from IWR1642 side?

It seems the HW trigger is enabled by high level instead of rising edge. Is this true?

Hi Chris,

I do not know about high level or rising edge trigger.

A possible solution for your customer regarding the frame start is setting the Pinmux to another port.

It has to be ensured that a high input on that pin triggers no other functions.

You can find this in the datasheet under Pin Attributes and the doxygen documentation for the pinmux driver.

file:///C:/ti/mmwave_sdk_01_02_00_05/packages/ti/drivers/pinmux/docs/doxygen/html/modules.html

However there should be a more elegant way.

Regards

Chethan,

Would you pls help to check if HW trigger is enabled by high level instead of rising edge?

hi, CHETHAN,

Could you help to check when HIGH-LEVEL is always at the SYNC-IN pin, at what time a frame will be triggerd?

In my experiement, trigger is level driven rather than pulse driven which is descripted in document and code.

Chethan,

Any update?

Chris,

SYNC_IN pin is hardware edge triggered, Please refer to below API document snippet from Radar Interface control document.

Could you please help us to locate the documentation stating "level driven rather than pulse driven".  

Also please ensure Sync_in rise time is fast (3-5ns) slower rise time and noise riding on the Sync-in pin might trigger Frame multiple times. 

Thanks and regards,

CHETHAN KUMAR Y.B.

Chethan,

Yes. The document says that the HW trigger works with rising edge. We don't find any doc says that HW trigger is level driven.

But based on customer's test when the input signal to SYNC_IN is always high, the frame will be triggered multi times and it seems that HW trigger works with high level. I will ask customer to check the noise on SYNC_IN when there is high level signal input. Will feedback later.

Hi, CHETHAN,

I could read a steady high level at the SYNC-IN pin, and i don't think it is caused by noise riding on SYNC-IN signal.

Why?

Because i have a frame intervel of 25ms by HW trigger， and connect LVDS data output to the signal scope. When trigger pulse is caused by noise, it may have a random interval of frame because the pulse edge cause by input signal is random. But i could see a steady and precise frame interval at 25ms.
So I am sure it is not caused by noise, which is obviously seen on the signal scope.

Could you plz reproduce the experiment by yourself and you could find more clue.

Thanks!