New type sonar with NMEA out

McKey · June 10, 2024, 3:23pm

Cheap sonars have appeared on the market, with a range of up to 6m, the minimum distance is 5 cm. I tested them by outputting data in nmea format (the readings are very accurate, as seen in the photo). These models come out under different names: L041MTW, L042MTW,GL041MT,GL042MT. More features on my Github. These sonars can be used in Sub to avoid obstacles. It can also be output via MAVLINK.

AlksSAV/Sonar-to-i2c-NMEA-: A cheap sonar project for autopilot based on Chinese modules. (github.com)

In the photo, the data is output via nmea 0183

McKey · June 15, 2024, 10:26am

Added a YouTube video with an example (in Russian)

Hi @rmackay9 , I think it’s possible to add information to the Wiki. I could prepare this on Github.

rmackay9 · June 15, 2024, 10:16pm

Hi @McKey,

Thanks for this.

Any chance you’d be interested in writing a Lua driver for these sonar to allow removing the need for the external arduino computer? We have two examples of this for other lidar here.

geofrancis · June 16, 2024, 7:13pm

I have this script for it but I havent been able to test it on a H7 controller, when it was made lua rangefinders wasnt a thing so i have added that option that but i havent tested it since.

github.com

geofrancis/GL041MT-Ardupilot/blob/main/GL04MT-Ardupilot-LUA.lua

local SCRIPT_NAME          = 'Depthfinder'
local MAV_DEPTH_LABEL      = 'DEPTH'
local BOOT_DELAY_MS        = 2000
local RUN_INTERVAL_MS      =  50
local SERIAL_PORT          =    0
local BAUD_RATE            = 115200
local FRAME_SIZE           =    4
local SPEED_RATIO          =    1
local INVALID_DEPTH        =   -1
local MAV_SEVERITY_WARNING =    4
local MAV_SEVERITY_INFO    =    6
local port = serial:find_serial(SERIAL_PORT)

port:begin(BAUD_RATE)
port:set_flow_control(0)

local function serial_flush(bytes)
    for i = 0, bytes - 1 do
        port:read()
    end

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kikislater · June 26, 2024, 5:35pm

Nice to see this project.
6m range is a bit limited IMO !

geofrancis · June 26, 2024, 7:11pm

It’s enough to stop you running aground or for a fish finder but thats about it.

kikislater · June 26, 2024, 7:28pm

It depends on plan to do with sensor. For bathymetric survey, it’s limited