Decoding tacktick micronet protocol

[trylimits]

I have the same motivation as the OP of this thread (How to build large format display), however, I target a tacktick micronet system (w/o Wireless Interface T122). The goal is to build a professionally looking mast display showing similar data as racegeek devices (+ performance against ORC polar, speed bar chart) for around 100$ total.

A month ago I started to decode the micronet protocol (European 868MHz version) and finally I'm able to fully decode and interprete the packets sent from the wind sensor T120, the dual display units T110 (including timer functionality) and the hull transmitter (speed, temp, depth and compass).
This can be done obviously without pairing my device first, which means that I'm also able to receive micronet data from nearby boats. Btw. it's also possible to inject false data into micronet networks (at least in absence of previously paired sensor devices).

What I cannot do yet is to add/send additional sensor data to the network. I would really like to cheaply add GPS data into our network or maybe do a complete 20$-rebuild of the T122.

If some of you are interested, I would like to publish the relevant information here - hopefully not facing any legal issues
If some of you have also done this before, I would be very interested in sharing the knowledge, since some bits of the protcol I still do not fully understand, respectively it would be very nice if my command list is getting more complete.

 

[WHK]

Since you have a means of decoding the micronet protocol, can you use the T122 and insert GPS data on the NMEA input, then decode on the micronet side?  On a side note, I have an old TackTick document that defines proprietary PTACK sentences.  If you are interested, I could send it to you.  I no longer have TackTick gear - it went when I sold my J/30.

 

[mustang__1]

so long as your goal is to have fun, have at! i think the system is too slow to do anything super meaningful... but as a nerd i'd love to copy whatever you do if i ever decide to race my boat again. 

 

[trylimits]

Since you have a means of decoding the micronet protocol, can you use the T122 and insert GPS data on the NMEA input, then decode on the micronet side?  On a side note, I have an old TackTick document that defines proprietary PTACK sentences.  If you are interested, I could send it to you.  I no longer have TackTick gear - it went when I sold my J/30.

That's exactly what I did to decode the other values, however, I do not have a T122 device to sniff GPS data packets. If I would have had a T122, I probably wouldn't have put any effort in decoding the micronet protocol anyways  Fallback plan is to sniff some tacktick traffic in a marina and hope someone has a micronet GPS device, even though this could be very time consuming.

I'm already familiar with the $PTAK sentences. The micronet protocol itself is not based on NMEA-like packets obviously.

so long as your goal is to have fun, have at! i think the system is too slow to do anything super meaningful... but as a nerd i'd love to copy whatever you do if i ever decide to race my boat again. 

It's indeed a fun project. Tacktick itself requests/answers data packets at a 1Hz rate, so yes, it's kinda "slow" compared to other sensor networks. However, keep in mind that the micronet network was initally designed and implemented in mid 2000s and (micro)processing-power was probably very limited at that time. Even if one could build a faster and cheaper system with today's technology, I really think it's amazing what they've built back then and lasting for so long. I really appreciate their work!

 

[Joakim]

It's indeed a fun project. Tacktick itself requests/answers data packets at a 1Hz rate, so yes, it's kinda "slow" compared to other sensor networks. However, keep in mind that the micronet network was initally designed and implemented in mid 2000s and (micro)processing-power was probably very limited at that time. Even if one could build a faster and cheaper system with today's technology, I really think it's amazing what they've built back then and lasting for so long. I really appreciate their work!

Sailing instruments do not require much of a processing power unless you are doing something special not done by most of the systems. The fist microcontroller based marine instruments came in the 80's and at least in the early 90's they were able to process all the data at several Hz.

I have made my own processing system that does everything needed at 4 Hz with a 8 bit microcontroller running at 2 MHz (this one could be run at 32 MHz, but there is no need for that). This includes calculating polars and calculating TWS, TWA and TWD etc. As a side job the processor also works as a solar power controller and battery monitor. It also drives a graphical display which I use to show all the data at the same time at the chart table. The same could have been done in the 90's easily. However it would have been more difficult to store all the data as my system does on a SD card.

I think the only reason for slow rate of Tacktick is due to save power for solar power operation. Also 1 Hz is fast enough for most of us, if the raw sensor data is already averaged out before sending.

 

[trylimits]

I think the only reason for slow rate of Tacktick is due to save power for solar power operation. Also 1 Hz is fast enough for most of us, if the raw sensor data is already averaged out before sending.

I agree. This is probably true.