AS7343 MicroPython

A MicroPython library for the AS7343 14-channel spectral sensor.

AS7343 is a 14-channel multi-purpose spectral sensor. It can detect 14 spectral channels - 12 in the visible spectrum (VIS) to near-infrared (NIR) range, a clear channel and flicker channel.

You can buy our AS7343 breakout here!

• AS7343 MicroPython
  • Installing
    • mip
  • Usage
    • Function Reference
      • set_gain
      • set_measurement_time
      • set_integration_time
      • set_illumination_current
      • set_illumination_led
      • start_measurement
      • stop_measurement
      • read
      • read_fifo
  • Hardware Details
    • Overview
    • Channels

Installing

mip

If your board is online and has mip you should be able to run:

import mip
mip.install("github:org/pimoroni/as7343-micropython/package.json")

Otherwise, using Tools -> Manage Packages in Thonny, locate the as7343-micropython package and install it as normal.

Usage

Basic example:

from as7343 import AS7343
from machine import I2C

i2c = machine.I2C(id=0, sda=20, scl=21)
as7343 = AS7343(i2c)

while True:
    readings = as7343.read()
    print(readings)

Function Reference

set_gain

Internally this sets AGAIN on the CFG1 register, which changes the spectral engines gain setting.

Valid values are 0.5, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 and 2048.

set_measurement_time

Set the total measurement time, this includes the integration time and the wait between readings.

Time is given in milliseconds and values from

set_integration_time

Set the portion of the measurement time which is actually used for sensor integration. This must be less than the total measurement time.

Time is given in microseconds, and longer times will increase the data output values and sensitivity of the sensor.

The granularity is 2.78us, and values up to 182,187us (182ms or roughly 1/5th a second) are supported.

The repeat (internally known as ASTEP) argument supports values from 1 to 256 and acts as a multiplier for the time.

The full scale ADC value is given as roughly:

repeat * integration_time_us

set_illumination_current

Set the current of the illumination LEDs.

Valid values are 4mA up to 258mA with increments of 2mA.

set_illumination_led

Enable the illumination LEDs, takes one value: True for on and False for off.

start_measurement

Flip the SMUXEN bit to start measurements into the internal FIFO.

This is done automatically the first time you call read().

stop_measurement

Clear the SMUXEN bit, stopping measurements. You should do this before changing gain and measurement settings.

read

Starts measurements (if they are stopped) and returns a dict contianing the sensor readings. By default this includes all eighteen channels from three read cycles.

read_fifo

Attempts to read a full set of data from the FIFO and returns the raw read results as a list in the order:

FZ, FY, FXL, NIR, VIS_TL, VIS_BR, FD
F2, F3, F4,  F6,  VIS_TL, VIS_BR, FD
F1, F7, F8,  F5,  VIS_TL, VIS_BR, FD

A list with this order is provided as AS7343.CHANNEL_MAP

Hardware Details

Overview

Uses six 16-bit ADCs switched over the 5x5 array via SMUX and then output sequentially into the 18-entry, 16-bit data registers.

Channels

Values for AGAIN 1024x, Integration Time: 27.8ms.

Irradiance responsivity values from figure 8.

Approximate colours from Figure 11.