AMS AS7341 Calibration Application Note

I’m learning the ropes of using an AMS AS7341 11-channel spectral color sensor, figuring out what I absolutely need and what I will wait to explore later. So far, I have found AMS product datasheet to be lacking. The topmost irritation was missing information on configuring the sensor multiplexor, a critical component inside the chip. It was also missing information on higher-level concepts for a color sensor and how the AS7341 implements them. I found some of this information in the document titled Spectral Sensor Calibration Methods which is listed as an Application Note Calibration Methods AS7341 EVKs.

This document taught me how an ideal spectral detector would activate on a specific wavelength, but real-world implementation is sensitive to a range of wavelengths near that target. This is why its documented response curve is a series of bell curves and not a set of spikes. Furthermore, there may be responses far from the target wavelength due to a variety of other factors.

This foundation led to an explanation of why, in addition to 8 different wavelengths within the visible spectrum, the sensor also had three additional sensors: A “Clear” sensor with no color filter, a near-infrared sensor, and a flicker detection system. Originally I had thought they were just thrown in for the sake of more features, but this application note explains they support the 8 color sensors by detecting problems that throw off readings.

I have to admit I did not understand much of the discussion about plotting sensor readings into CIE color space. Color science is a field with a long history and reading Wikipedia pages only taught me that there is a lot I don’t know. Clearly this application note is aimed at an audience who is already familiar with the topic.

But even if I was familiar with CIE color spaces, this document left a lot of gaps in information. This application note referenced a piece of software called “AS7341 Software GUI, running on a Windows personal computer” but that software is nowhere to be found on AMS website. It appears to be something I can obtain by contacting my AMS account representative, which I don’t have. There are also snippets of a large Excel spreadsheet, with the disclaimer “Tables were interrupted. See the full tables in the original MS Excel File.” And is this MS Excel file on the website? Apparently not: “Ask the ams support team for the original XLS file” And there was a section that ended with “For more details, please refer to the Sensor ECGs manual.” What is ECG? That was not explained. And so on.

I learned a lot from AMS documentation for AS7341 but I felt there were significant room for improvement. Nevertheless, I am confident enough in my understanding to get hands-on with AS7341 sensor.

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