Number of fans limited by firmware?

TechNi · 18 Jul 2021, 08:40

With the new Duet 3, you can add basically infinite expansion boards. There's probably a limit somewhere but currently it seems like it's being dictated by the firmware and not the hardware?

I have LEDs on my printer which are seen by the firmware as "fans". I have the problem that I am running out of numbers. Apparently 16 fans are already too much as I am getting the following error:

M950: parameter 'F' too high

I can't define M950 F16 or F17 but I need two more fans. And I have plenty of free sockets thanks to the expansion boards. But the firmware seems to limit this. Is there any workaround or update coming to solve this matter?

peter247 · 18 Jul 2021, 09:50

@techni Why don't you use Neopixels leds where you can have 60 or more with just 1 pin.

Phaedrux · 18 Jul 2021, 16:15

Maybe create it as a switchable IO pin instead and use M42 to control them?

https://duet3d.dozuki.com/Wiki/Using_servos_and_controlling_unused_IO_pins

M950 P instead of F

dc42 · 18 Jul 2021, 16:35

@techni these are the current limits for Duet 3 systems:

// Limits of Duet 3 systems
constexpr size_t MaxSensors = 56;						// limited by the size of bitmap we can store in an ExpressionValue
constexpr size_t MaxHeaters = 32;
constexpr size_t MaxMonitorsPerHeater = 3;

constexpr size_t MaxZProbes = 4;
constexpr size_t MaxZProbeProgramBytes = 8;				// maximum number of bytes in a Z probe program

constexpr size_t MaxFans = 16;

constexpr size_t MaxGpOutPorts = 32;					// increased as requested by Jimmykc

// The following currently don't need to be known by expansion boards, but might in future
constexpr size_t MaxGpInPorts = 16;
constexpr size_t MaxSpindles = 2;						// maximum number of configurable spindles

I can increase MaxFans in the next 3.4beta.

TechNi · 18 Jul 2021, 16:55

@dc42 said in Number of fans limited by firmware?:

I can increase MaxFans in the next 3.4beta.

That would be cool! I guess there's a good reason for these limitations but I am sure the Duet can handle this.

@peter247 Neopixels are kinda expensive compared to "normal" LED strips and I'd like to be flexible.

@Phaedrux Did not know you could do that, thanks!

TechNi · 16 Aug 2021, 18:28

@dc42 Hey dc42, I know minor issues like this are not exactly a priority on your list but any chance that this is now fixed in the new RRF 3.4.0 beta 2? I did not find anything in the changelog. Would greatly appreciate this small fix. Thanks!

bot · 16 Aug 2021, 19:30

@techni see if you can follow the build instructions, and modify the value yourself and compile. It shouldn't be too hard.

kb58 · 16 Aug 2021, 19:35

If any of these fans are turned on and off at the same time, just wire them in parallel, first checking of course that the driver can handle the total current.

dc42 · 16 Aug 2021, 20:13

@techni I will increase the maximum number of fans to 20 in the next beta.

TechNi · 25 Aug 2021, 08:24

@dc42 Morning, was this finally solved in RRF 3.4b3?

dc42 · 25 Aug 2021, 08:51

@techni said in Number of fans limited by firmware?:

@dc42 Morning, was this finally solved in RRF 3.4b3?

Yes, I increased the maximum to 20.

TechNi · 25 Aug 2021, 10:23

@dc42 Many thanks!

TimMacey · 31 May 2022, 11:57

I have an application that needs 24 fans. Is there a means to do this? I'm running a 6HC MB with 7x 3HC extension boards.

dc42 · 31 May 2022, 12:40

@timmacey currently (using RRF 3.4) you could only be able to control 20 at once as fans, but you could configure the remaining 4 as GpOut pins and control them using M42. I can increase the maximum number of fans in RRF 3.5.

dc42 · 22 Nov 2024, 11:24

@TimMacey the maximum number of fans was increased to 32 in RRF 3.5.