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More thoughts on DemoBoard and pcb redesign

A project log for Compact, $25 spectrometer

AMS's new AS7265X 3-chip set promises a compact, 18-channel, 20 nm FWMH spectrometer for less than $25

kris-winerKris Winer 04/23/2018 at 19:430 Comments

April 23, 2018

I didn't appreciate it at first but the UART interface via FTDI connector that is the default with the DemoBoard allows the sensor to work without an MCU. The AS7265X sensor set is configurable by the AMS-supplied GUI with which the data can be captured and stored for later plotting. This is a pretty convenient way to use the spectrometer.

I intend to use an MCU and set the I2C interface as default on my spectrometer design. But I should be able to also make it work with the FTDI connector by simply connecting the I2C enable (CEN on the board) to GND and using SDA/SCL as UART RX/TX. We'll see if the pullups get in the way.

One thing I learned from the DemoBoard is that exposing the SPI port to load the required firmware onto the SPI flash is needed. There is some discussion in the AS7265X data sheet of loading firmware directly via I2C to the AS7265X. I think this is for the case where there is no SPI flash and the firmware needs to be loaded to the sensor from the host. But I don't know. I was hoping I could load the SPI flash with firmware by this method, and I might still be able to. But I decided to redesign the pcb to add the SPI port just in case this doesn't work.

I still haven't gotten an answer to my queries from AMS. I might just have to copy the firmware from the SPI flash on the demoboard. The AS7265X chip set won't become available for purchase until mid-May which should be just around the time I get these boards back from OSH Park. So I hope to have a working design by then...

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