Thread: Poor mans Ipilot

Anxiously waiting, Wayne.

Looking forward to seeing more photos and reading your reports.

You've got a bigger project creating the steering and speed control than I do. Starting with a terrova with copilot and a HB 768 we can skip most of the mechanical steps. I think I'm going to buy a spare remote and steal the board. The remote board will go into the box with the control board. This way all we'll need to do is get the control board to activate the left/right and +/- speed inputs on the remote board. Only thing left will be an activate/deactivate control, a momentary override, and a "set" for the speed.

Guess I was trying to ask(being a lazy ike) if you would share your code, or the sites where you got some of your code. We won't be able to use the activation commands as they are, but your code for grabbing the NMEA output would be very helpful. If not I understand completely.

You can do it Wayne. I would think the linkage would be the easy part. Your downhill from here.

Originally Posted by papadave

Looking forward to seeing more photos and reading your reports.

You've got a bigger project creating the steering and speed control than I do. Starting with a terrova with copilot and a HB 768 we can skip most of the mechanical steps. I think I'm going to buy a spare remote and steal the board. The remote board will go into the box with the control board. This way all we'll need to do is get the control board to activate the left/right and +/- speed inputs on the remote board. Only thing left will be an activate/deactivate control, a momentary override, and a "set" for the speed.

Guess I was trying to ask(being a lazy ike) if you would share your code, or the sites where you got some of your code. We won't be able to use the activation commands as they are, but your code for grabbing the NMEA output would be very helpful. If not I understand completely.

Sure, I'll share my work. Are we talking about VB, C# or C++ programming?The NMEA 0183 data stream consists of a series of "sentences" delimited by a newline character. Each sentence begins with a six character identifier, the first character of which is always "$". The NMEA 0183 standard defines dozens of sentences, but only a fraction apply directly to GPS devices. The sentences we need include:

• $GPAAM - Waypoint Arrival Alarm
• $GPBOD - Bearing, Origin to Destination
• $GPBWW - Bearing, Waypoint to Waypoint
• $GPGGA - Global Positioning System Fix Data
• $GPGLL - Geographic Position, Latitude/Longitude
• $GPGSA - GPS DOP and Active Satellites
• $GPGST - GPS Pseudorange Noise Statistics
• $GPGSV - GPS Satellites in View
• $GPHDG - Heading, Deviation & Variation
• $GPHDT - Heading, True
• $GPRMB - Recommended Minimum Navigation Information
• $GPRMC - Recommended Minimum Specific GPS/TRANSIT Data
• $GPRTE - Routes
• $GPVTG - Track Made Good and Ground Speed
• $GPWCV - Waypoint Closure Velocity
• $GPWNC - Distance, Waypoint to Waypoint
• $GPWPL - Waypoint Location
• $GPXTE - Cross-Track Error, Measured
• $GPXTR - Cross-Track Error, Dead Reckoning
• $GPZDA - UTC Date/Time and Local Time Zone Offset
• $GPZFO - UTC and Time from Origin Waypoint
• $GPZTG - UTC and Time to Destination Waypoint

For the sake of simplicity, let's just say that we are only interested in position, speed, and course data. Looking at the available NMEA 0183 sentences, we see that the $GPRMC sentence contains all the information we need. The format of the $GPRMC sentence is

$GPRMC,aaaaaa,b,cccc.cc,d,eeeee.ee,f,ggg.g,hhh.h,j jjjjj,kkk.k,l*mm

Where:

• aaaaaa is the time of the fix UTC in hhmmss format
• b is the validity of the fix ("A" = valid, "V" = invalid)
• cccc.cc is the current latitude in ddmm.mm format
• d is the latitude hemisphere ("N" = northern, "S" = southern)
• eeeee.ee is the current longitude in dddmm.mm format
• f is the longitude hemisphere ("E" = eastern, "W" = western)
• ggg.g is the speed in knots
• hhh.h is the true course in degrees
• jjjjjj is the date in DDMMYY format
• kkk.k is the magnetic variation in degrees
• l is the direction of magnetic variation ("E" = east, "W" = west)
• mm is the checksum

Getting the position, speed, and course data in which we are interested now just becomes a matter of reading the $GPRMC sentence into a string, parsing the string to extract the pertinent data, and converting the data into the proper units, simple as that. Its all pretty basic programming with the above info, simply (mostly) IF THEN statements, Its really not as hard as it looks, but my code wont work for the application you have in mind due to the fact I had to make it read from my boards com ports.

I understand. 95% of the string data is useless. Did you get a chance to look at any high speed linear actuators?

Nice to meet you at Sardis.

Originally Posted by Cane Pole

I understand. 95% of the string data is useless. Did you get a chance to look at any high speed linear actuators?

Nice to meet you at Sardis.

It was very nice to meet ya'll too!
I have been looking at actuators, just haven't found anything that trips my trigger yet, most are way too expensive! I'm not totally convinced that I should drive it from the foot pedal. I'm still looking at ways to build something that could be connected to the shaft and fit ANY motor and then be disconnected quickly, easily and securely. The ideal way to steer would be from the inside where the gears mesh with the shaft, but that would be entirely to difficult to install across several models of trolling motors, what I need is a universal fit that can easily be adapted to various models of trolling motors. I really think the answer lies within the shafts. Like I said, there are plenty ways to make this work but I truly would like to make a poor mans Ipilot, reason being......I'm poor! At the same time make it do the things I need it to do. It may never work, but it sure won't be from lack of effort

This is amazing to me. I have heard nothing but good things about you Wayne. Keep us posted.

Ok guys, it's been a while but the unit is doing a awesome job at pulling crankbaits! I finally figured out the hardware and been making adjustments to the software. I'll be making a few demo videos of the entire unit and what it will and won't do. I had a time with the patent attorneys because of another unit presently on the market but they figured it out and it's forward we go with the project. Main objective here is a add-on autopilot for a foot pedal trolling motor or tiller mount that uses your gps waypoints, tracks and routes. I'm also going to build a PC program to build new routes from logged data at home. Stay tuned, this could get interesting!