Futaba -868/915mhz equipment

Okay.... to be fair, i have decided that Futaba now needs its own sub category for posting information regarding their own in house 900mhz system.

Following is the posts originally in the "868/915 Mhz as a viable frequency for Submarines" topic:

Edited on 3/12/24

Not saying this is "New", but i just found out that Futaba supports "CRSF" protocol output on a few of its radios.

a short list of known transmitters that allow you to connect either an expresslrs or tbs-crossfire module:

Futaba 12K
Futaba 16sz
Futaba 16iz
Futaba 18sz
Futaba 32mz
Futaba fx-36

however, this has one or two caveats depending on which model transmitter you are using:

none of the transmitters supports bidirectional (telementry) data transfer. the protocol is outbound only, it is basically changing what was the s.bus output, and allowing it to support both s.bus and crsf. there are only 3 wires on the connecter (gnd, vcc, tx) so the inbound (rx) pin does not exist.

on the 12k, 16sz, and 16iz, the power line is not available, so a secondary power input needs to be used to provide power for the module.


This was basically provided over 4 years ago as a firmware update for the radios that existed at that time, and all new radios out of the box since then.

Given the cost of these radios ($450-$3000) i would only recommend this option for someone that already owns one of these radios,
since any of the opentx/edgetx or ethos based radios fully support crsf/expresslrs (including telemetry) for considerably less money.

*it appears that the 12k was unofficially supported in version 3 of the firmware. it has since been updated to version 4 of the firmware, and at that time crsf support was removed.


----- addendum as of 4/29/2024 -----

I went ahead and bought a Futaba 18sz, and verified that yes, it does support CRSF from the "S-I/F" port on the back of it. this port is normally used to upgrade/configure devices that use futaba's s-bus protocol (servos, gyros, power boards) and when you have that port configured for CRSF output, it will work with either the TBS-Crossfire modules or the ExpressLRS modules that have advanced funtionality. basically, the radio itself does not support any additional functionality, so anything that does not have its own capability of doing things like binding or configuring output power will not work on this radio. I do own both the TBS Crossfire nano module and several ExpressLRS modules that have displays and controls to allow configuration and binding, and testing did show that all the functionality needed for bare minimum use is available. As stated earlier, there is no two way communication, so telemetry is not supported.

Unlike my vintage futaba radios, there is nothing but a simple 3 wire connector needed to support ExpressLRS (no ppm to crsf converter needed), the "S-I/F" port is a standard 3 pin servo port, so a $3 servo extension wire and a 3 pin round 2.54mm pin header are all that is needed to connect a module.

----- addendum as of 5/30/2024 -----

I got word from Futaba USA that firmware v4.1 has been released for the Futaba t12k, and it re-introduces the CRSF protocol on that radios S-I/F port. You now have a range of futaba radios from the $460 12k to the $3000 32mz if you want to run submarines with new futaba radios.


Last edited by tsenecal on Thu May 30, 2024 1:21 pm; edited 4 times in total

Futaba has its own 900mhz module & receiver.

Futaba TM-18 module & r9001sb receiver.

https://www.rc.futaba.co.jp/products/detail/I00000320

This works in conjunction with the CRSF update for their specific radios (you need to have the crsf protocol support to use this module)

I have seen different reports about its use, some reports indicate it is a backup system, to be used in conjunction with either the native fasst or fhss 2.4ghz protocol supported by the host transmitter. At the very least, as with all CRSF modules on the futaba radios, this module does not support telemetry because there is no RX equivalent pin on the connector.


I have not found enough information regarding the actual hardware used, and do not know if the TM-18 module will work with other CRSF based receivers. (tbs-crossfire or expresslrs)

The following systems were purchased by me to test the Futaba system.  I have cobbled together enough equipment to get a working system in order, and i will have this installed in one of the submarines at the annual regatta i go to in California USA.  This years regatta (2024) is scheduled for September 28th and 29th, so i have a while to do some in house testing prior to that.

This is Futaba's T18sz transmitter, with their TM-18 900mhz module, and r9001sb receiver.  the receiver basically has a single pwm output and a single s-bus(2) output, so to work with our subs, i have added a 16 channel s-bus decoder, and have three servos wired into it.  I have not yet decided what submarine i will be using for the test bed, but there are several i can choose from, and i will post here which one it ends up being.

Not sure if i will or not, but i have a lead on an inexpensive futaba T12k transmitter as well.  It might be worth my while to pick that up, since i now know that radio will also work with any CRSF transmitter module (TBS/ELRS/Futaba).

It might also be interesting to see how well the futaba TM-18 works with other CRSF capable transmitters.

So I did make it to the San Francisco fun run this year, and as one of the setups i took:

Bronco Type XXIII with Futaba r9001sb receiver
Futaba 18sz with TM-18 transmitter module

It performed as expected, zero issues as far as the radio goes, need to do some more trimming of the boat to get it to work as well as it could.

one small concerning issue regarding the r9001sb receiver that Futaba's 915mhz system uses.

channel 3 is the only channel that has a preset failsafe condition, and it only activates after 1 second of loss of signal. ALL other channels failsafe to a HOLD condition, meaning that whatever value the "servo" was set to at the time of failsafe, is the value it will stay at until signal is regained.

i specifically configured my system so that channel 3 is used for the ballast tank, with the failsafe setting so it will empty the tank, forcing sub to surface, but i don't like the fact that this specific setup does not follow Futaba's tradition of allowing you to set presets for all channels.