Firmware limitations on 1MB flight controllers, and terrain and Smart RTL issues

Hi folks,

I didn’t really realize til today that some flight controllers don’t have enough ram (flash memory?) to hold the entire Arucopter firmware (after using Arducopter for 7 years…yeesh). Apparently, ALL my flight controllers are limited to 1MB. I have an original Pixhawk and 2 Kakute F7’s at the moment.

So a couple questions:

  1. Do any of the “small” flight controllers have enough ram to hold the entire firmware plus terrain and Smart RTL breadcrumbs? (Would that be 2mb+?) I’m speaking of flight controllers like the Holybro Kakute F7, and so many others that are similar? I really like their size/weight.

  2. I would like to have onboard TERRAIN data (for terrain-following without connection to a GCS), as well as the ability to use Smart RTL. Can I assume right now that my 1MB flight controllers have NO ROOM for those items?

  3. Is there any plan to offload some of this data to the SD card? All my flight controllers have an SD card, so if those could be used for terrain data and Smart RTL bread crumbs, that would be great.

  4. My “freemem” on a Kakute F7, after loading Copter 4.0.4, says 65535…I assume that’s 65k?

Oh, and BTW, how long/far can a person fly before, say, 300k of breadcrumbs are filled up?


Matek F765-Wing & Matek H743-Wing (coming soon) have 2Mb flash. Frsky R9 Pilot if it actually exists…


Thanks. Do you know if the R9 Pilot will have an integrated R9 receiver? Sorta seems obvious given the nomenclature, but I can’t find any specific info.


The hwdef file says this:
UART8, marked “RX RFD”, connected to RXSR receiver via
7-pin ribbon cable

So, direct connection but level of integration is not clear. I don’t normally point to YouTube videos as there is so much junk out there but Paweł Spychalski did one on it and his videos are informative and great fun.

I like Pawel as well…fun guy.

So they showed it connected to an RXSR? Kinda weird since that’s not a 900mhz receiver.


Apparently they have an 2.4Ghz and a 900Mhz Rx with a ribbon cable to connect to the board. At least that’s what they gave Pawel. Frsky announced this board in 2017 so who knows when it it will be available. Matek and Holybro have come out with families of Flight Controllers since then!

Replying to myself…I found that terrain data goes on the SD card, and Smart RTL only uses 3k per 100 points? (I thought is was 300k…I swear I read that in multiple places)…so, with my 65k free, looks like I’ll have no problem using Smart RTL.

Right? :slight_smile:

Right. I had a “…buffer full” error with a PixRacer craft but found I had accuracy set to 2m and max points to 300. That craft has flown 14km missions with battery to spare.