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