openmv/scripts/libraries/I2C_Lidar_Lite_V3_example_code.py
2023-02-19 21:13:21 +01:00

64 lines
2.5 KiB
Python

# OpenMV M7 I2C interface with Garmin Lidar Lite V3 - By: Grant Phillips - Sun Apr 8 2018
# Returns a basic distance reading from the lidar in cm for the target point and prints to console
# Uses default lidar settings. For more advanced settings, see the I2C commands in the manual:
# https://static.garmin.com/pumac/LIDAR_Lite_v3_Operation_Manual_and_Technical_Specifications.pdf
# I2C Control of LIDAR Lite V3
# 1. Write 0x04 to register 0x00
# 2. Read register 0x01. Repeat until bit 0 (LSB) goes low.
# 3. Read two bytes from 0x8f (high byte 0x0f then low byte 0x10) to obtain 16 bit measurement in cm
# HARDWARE CONNECTIONS:
# Connect the lidar SCL line (green) to I2C 2 SCL on openMV (Pin 4)
# Connect the lidar SDA line (blue) to I2C 2 SDA on openMV (pin 5)
# 680uF filter capacitor in parallel with the lidar
# 10k pullup resistors on the SCL and SDA lines to +5Vdc
import pyb
from pyb import I2C
lidarReady = bytearray([0xFF]) # holds the returned data for ready check
lidarReadyCheck = bytes([1]) # to compare bit 0 of lidarReady
startBuf = bytearray([0x00, 0x04]) # step 1 address and data
readyBuf = bytearray([0x01]) # step 2 address for readiness check
distBuf = bytearray([0x8F]) # step 3 address for distance reading
distance = -1 # variable for distance reading
# I2C setup
Lidar = I2C(2, I2C.MASTER) # initialise I2C 2 bus in master mode
while True:
distance = -1 # reset to -1 so we know when we get a real reading
try: # handles errors thrown up if we have an I2C error
# Step 1 Write 0x04 to register 0x00
Lidar.send(startBuf, 0x62) # this is making it read (laser visible)
# Step 2 Read register 0x01 and wait for bit 0 to go low
while lidarReady[0] & readyBuf[0]:
Lidar.send(readyBuf, 0x62)
lidarReady = Lidar.recv(1, 0x62)
pyb.delay(50) # This seems to help reduce errors on the I2C bus
lidarReady = bytearray([0xFF]) # reset the ready check data for next reading
# Step 3 Read the distance measurement from 0x8f (0x0f and 0x10)
Lidar.send(distBuf, 0x62)
dist = Lidar.recv(2, 0x62)
distance = dist[0]
distance <<= 8 # move 2 bytes into a 16 bit int
distance |= dist[1]
pyb.delay(100) # allow time between readings, can go faster but more errors
except OSError: # reninitialise i2c bus if error
Lidar.init(I2C.MASTER)
print("error, reinitialising")
if distance > -1:
print("Distance:", distance, "cm")