Hi team,
Our customer is using a PGA460, but has the following issues, please help replying.
What does Preset1 and Preset2 do?
When to use it?
How do I use it?
How does it relate to the AFE gain setting?
Can it be OK to only change the AFE gain when detecting a few mm of objects?
Best Regards,
Amy
Amy,
Thanks for reaching out with your question.
The time varying gain in the AFE is shared between both presets, so care should be taken to set this based on the setting with the longest record length.
The presets allow the user to program two different threshold profiles and burst settings into the device to facilitate quickly switching operating modes with the same hardware configuration. We typically recommend configuring P1 for short range detection and P2 for long range.
Each preset has its own set of registers which require programming at initialization. Once setup, the CMD bits used during UART communication will specify burst or listen on either preset 1 or 2.
You can find some additional details and guidance for using PGA460 in the document below
Hi Scott,
Thank you for your response!
The focus of the customer's question is Preset1 and Preset2 in the block diagram on page 17 of PGA460-Q1 datasheet, as shown below:
The two thresholds in the road are compared to the signal after being selected by MUX. Here's a question:
Is the signal compared to the threshold （TH_Px_L1。。。。。TH_Px_L12）of the corresponding point （H_Px_T1-------H_Px_T2--------。。。。。。H_Px_T12）every time it goes? What dimension or unit was the comparison result?
In other words, because our customer does't know how thresholds relate to distance measurements, so he does not know how to adjust parameters such as thresholds and gains
Also, the customer did not purchase the PGA460EVM and was debugged using a board of their own design, so various parameters need to be set by themselves. The purpose is to detect objects with a minimum width of 3mm from 3 to 10cm.
Amy,
The thresholds are selected based on the command given at the start of the conversion. Whether profile 1 or profile 2 is used will depend on the particular run command they send. This allows them to adjust the device settings for their particular need:
Instead of comparing the thresholds to each other, they are being compared to the processed echo signal over the full duration of the listen period. Sound waves attenuate as they propagate and therefore at longer listening times the expected return signal will have a lower magnitude.
The value of the threshold is compared directly to this echo data which produces a High/Low signal which controls the behavior on the IO pin. Based on the filter and digital gain settings, a different time varying response will be observed. The echo data processing can be monitored using the data dump feature which allows for optimization of their solution.
To optimize the threshold levels, it will likely be necessary to evaluate the echo response data dump for the target at various ranges to ensure the echo is accurately recorded. Once a profile for the desired echo is established, the threshold levels can be set as needed.
The ability to detect the target may vary based on the output configuration (direct or transformer) which will impact the burst strength the transducer can generate. Additionally, the specifications of the selected transducer should also be considered. For instance, higher frequency transmissions attenuate faster and can therefore limit the maximum sensing range of the solution.
The EVM and GUI does help with this development process and will help make the settings more intuitive. If they continue to have trouble with evaluating their threshold settings, it would likely be helpful to purchase this help determine the settings they will want for their application.
Thanks,
Scott
