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Added script to measure optical crosstalk (#3)
Authored-by: David Smith
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‎README.md‎

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## Files
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The project consists of 2 files:
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The project consists of 3 files:
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- **tmf8806_read_cal_data.py** - CircuitPython script to configure TMF8806, start factory calibration and print out calibration data
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- **tmf8806_basic_example.py** - CurcuitPython script to configure TMF8806, load factory calibration, start measurements and print out TID, Distance and confidence
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- **tmf8806_read_xtalk.py** � CircuitPython script to perform a series of crosstalk measurements. The minimum, maximum and average crosstalk values are printed to the shell window
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- **tmf8806_basic_example.py** - CircuitPython script to configure TMF8806, load factory calibration, start measurements and print out TID, Distance and confidence
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## Factory calibration
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The tmf8806_read_cal_data.py script outputs a string of 14 bytes that should be copied to the tmf8806_basic_example.py script cal_data variable.
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## Measure optical stack crosstalk
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It is important that the crosstalk generated by the optical stack is within the limits stated within the TMF8806 Optical Design Guide (PD001060). The script will run a set number of measurements and print out the minimum, maximum and average crosstalk values.
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## Basic device configuration and continuous measurement example
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The tmf8806_basic_example.py will configure the sensor with the defualt settings as described in the TMF8806 datasheet(DS001097) and TMF8806 Host Driver Communication Application Note (AN001069) section 8.8. The script includes several other configuration examples which can be used to change the basic device configuration.

‎tmf8806_read_xtalk.py‎

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# /*****************************************************************************
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# * Copyright (c) [2024] ams-OSRAM AG *
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# * All rights are reserved. *
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# * *
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# * FOR FULL LICENSE TEXT SEE LICENSE.TXT *
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# ******************************************************************************/
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"""
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TMF8806 Circuitpython v8.0.5 implementation specific to the RP2040 (Pin layout)
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Configure device, read xtalk
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"""
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import time
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import board
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import busio
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import digitalio
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"""
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Constants
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"""
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SLAVE_ADDR = 0x41
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BSL_SLEEP = 0x00
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BSL_READY = 0x41
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PON = 0x01
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APP0 = 0xC0
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CLR_INT = 0x01
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EN_INT = 0x01
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RES_INT = 0x01
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I2C_FREQUENCY_1MHz = 1000000
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NUMBER_OF_MEASUREMENTS = 100
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"""
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TMF8806 register addresses
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"""
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app_req_id_reg = 0x02
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cmd_reg = 0x10
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stat_reg = 0x1D
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factory_cal_reg = 0x20
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enable_reg = 0xE0
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int_stat_reg = 0xE1
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int_en_reg = 0xE2
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"""
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Variables
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"""
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result = bytearray(7)
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int_stat_result = bytearray(1)
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number_of_measurements = 100
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xtalk_min = 1000000
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xtalk_max = 0
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xtalk_avg = 0
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"""
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Alternate command data strings, changes period & # of iterations
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Command = [addr, cd9, cd8, cd7, cd6, cd5, cd4, cd3, cd2, cd1, cd0, cmd]
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Command = [addr, emc, ss, cal/st, alg, gpio,gpiot,thres,rep_ms,it_lsb,it_msb,start]
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start_measure = [0x06, 0x00, 0x00, 0x11, 0x02, 0x00, 0x00, 0x06, 0xFE, 0x0A, 0x00, 0x02] # 1Hz continuous sample rate, 10k iterations
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start_measure = [0x06, 0x00, 0x00, 0x11, 0x02, 0x00, 0x00, 0x06, 0xFE, 0xFF, 0x01, 0x02] # 1Hz continuous sample rate, 511k iterations
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start_measure = [0x06, 0x00, 0x00, 0x11, 0x02, 0x03, 0x01, 0x00, 0xC8, 0x01, 0x00, 0x02] # 10Hz continuous sample rate, 900k iterations
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start_measure = [0x06, 0x00, 0x00, 0x11, 0x02, 0x00, 0x00, 0x06, 0x1E, 0xA0, 0x0F, 0x02] # 10Hz continuous sample rate, 4000k iterations
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start_measure = [0x06, 0x00, 0x00, 0x11, 0x02, 0x00, 0x00, 0x06, 0x1E, 0x84, 0x03, 0x02] # 30Hz continuous sample rate, 900k iterations
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"""
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start_measure = [0x06, 0x00, 0x00, 0x11, 0x02, 0x00, 0x00, 0x06, 0x1E, 0x84, 0x03, 0x02] # 30Hz continuous sample rate, 900k iterations
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"""
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Calibration data - individual to each device
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"""
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cal_data = [factory_cal_reg, 0x02,0x00,0x00,0xF9,0xCF,0xE0,0x3F,0x7F,0x03,0x00,0x40,0x20,0x00,0x04]
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"""
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Configure TMF8806 Enable pin
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"""
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tmf8806_enablepin = digitalio.DigitalInOut(board.GP16)
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tmf8806_enablepin.direction = digitalio.Direction.OUTPUT
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"""
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I2C setup
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"""
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tmf8806 = busio.I2C(scl=board.GP7, sda=board.GP6, frequency = I2C_FREQUENCY_1MHz)
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"""
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Function definitions
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"""
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def enable_tmf8806():
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"""
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Function to enable TMF8806 device
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"""
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res = bytearray(1)
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tmf8806_enablepin.value = False # pull enable pin low for 3 milliseconds to allow cap to discharge
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time.sleep(0.003)
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tmf8806_enablepin.value = True
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time.sleep(0.002) # 2ms boot time
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tmf8806.writeto_then_readfrom(SLAVE_ADDR, bytes([enable_reg]), res) # read state of device
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while (res[0] != BSL_SLEEP):
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tmf8806.writeto_then_readfrom(SLAVE_ADDR, bytes([enable_reg]), res)
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tmf8806.writeto_then_readfrom(SLAVE_ADDR, bytes([enable_reg, PON]), res) # wake-up device
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while (res[0] != BSL_READY):
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tmf8806.writeto_then_readfrom(SLAVE_ADDR, bytes([enable_reg]), res)
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tmf8806.writeto_then_readfrom(SLAVE_ADDR, bytes([app_req_id_reg, APP0]), res)
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tmf8806.writeto_then_readfrom(SLAVE_ADDR, bytes([app_req_id_reg]), res) # check the App Id here to make sure app is running
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while (res[0] != APP0):
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tmf8806.writeto_then_readfrom(SLAVE_ADDR, bytes([app_req_id_reg]), res)
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def load_cal():
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"""
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Load calibration data to device
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"""
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tmf8806.writeto(SLAVE_ADDR, bytes(cal_data))
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def start_measurements():
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"""
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Write command data string to TMF8806 device
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"""
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tmf8806.writeto(SLAVE_ADDR, bytes([int_stat_reg, CLR_INT])) # clear any outdated (but still pending) interrupt (e.g. from previous run)
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tmf8806.writeto(SLAVE_ADDR, bytes([int_en_reg, EN_INT])) # enable interrupts before starting to measure, so to not miss the first one
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tmf8806.writeto(SLAVE_ADDR, bytes(start_measure)) # send command string
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"""
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Main code - Wait for result ready flag and measure crosstalk levels, print min, max and average value for 100 measurements
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"""
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while not tmf8806.try_lock():
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pass
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try:
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enable_tmf8806() # pull enable pin high and wait for CPU ready
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load_cal() # load factory calibration information
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start_measurements() # start continuous measurements as per start_measurement configuration
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tmf8806.writeto_then_readfrom(SLAVE_ADDR, bytes([int_stat_reg]), int_stat_result) # just read 1 byte
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print("Measuring crosstalk, please wait...\n")
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for loop in range(NUMBER_OF_MEASUREMENTS): # loop for "number_of_measurements" measurements
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while (int_stat_result[0] != RES_INT): # poll interrupt flag for result ready indication
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tmf8806.writeto_then_readfrom(SLAVE_ADDR, bytes([int_stat_reg]), int_stat_result)
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tmf8806.writeto(SLAVE_ADDR, bytes([int_stat_reg, CLR_INT]))
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tmf8806.writeto_then_readfrom(SLAVE_ADDR, bytes([0x3C]), result) # read result block
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if (result[0] + 0xFF * result[1]) < xtalk_min: # is this the lowest crosstalk measurement?
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xtalk_min = (result[0] + 0xFF * result[1])
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if (result[0] + 0xFF * result[1]) > xtalk_max: # is this the highest crosstalk measurement?
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xtalk_max = (result[0] + 0xFF * result[1])
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xtalk_avg = xtalk_avg + (result[0] + 0xFF * result[1]) # sum xtalk for average calculation
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tmf8806.writeto_then_readfrom(SLAVE_ADDR, bytes([int_stat_reg]), int_stat_result) # reset interrupt for next measurement result
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print("Crosstalk minimum value:", xtalk_min) # print min, max and average results
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print("Crosstalk maximum value:", xtalk_max)
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print("Average of 100 measurements:",round(xtalk_avg/NUMBER_OF_MEASUREMENTS))
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finally:
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tmf8806.unlock()
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