Hi there, sorry if this is in a thread already, I couldn't find it.

I'm playing an Artillerist Artificer right now, and I'm at level 11. My DM has only recently starting targetting the eldritch cannon to reduce its HP, and I've noticed that I've got to reduce the HP 1-by-1 whenever it takes damage, and also that when I take a long rest, the HP that the cannon has doesn't reset back up to full... which means increasing, 1-by-1 again, to 55. 

Is there another way to do this that I'm missing? I can't see a 'reset' button anywhere, and since it's real tedious to change the HP, it means I've been keeping track of the HP in a notepad instead.

I believe you're right. I thought  the Long Rest option above the cannon lists would reset it if you long rested, but that does not appear to be the case.

I am thinking, that perhaps action needs to be taken (bonus action?) to repair the cannons and long rests don't reset their "HP" as they're not living and benefiting from a long rest? I'd need to read up more on the class. (I've not allowed Artificers in my game until very recently so they're admittedly my weakest knowledge spot).

 EDIT: Ah ha! Just read the class and noticed when it talks about the cannons...

If the mending spell is cast on it, it regains 2d6

So you resting will not heal it. You would need to cast mending.

And then manually increase (unfortunately, increments of 1)

https://www.dndbeyond.com/classes/artificer#Artillerist

Eldritch Cannon
3rd-level Artillerist feature

You've learned how to create a magical cannon. Using woodcarver’s tools or smith’s tools, you can take an action to magically create a Small or Tiny eldritch cannon in an unoccupied space on a horizontal surface within 5 feet of you. A Small eldritch cannon occupies its space, and a Tiny one can be held in one hand.

Once you create a cannon, you can’t do so again until you finish a long rest or until you expend a spell slot to create one. You can have only one cannon at a time and can’t create one while your cannon is present.

The cannon is a magical object. Regardless of size, the cannon has an AC of 18 and a number of hit points equal to five times your artificer level. It is immune to poison damage and psychic damage. If it is forced to make an ability check or a saving throw, treat all its ability scores as 10 (+0). If the mending spell is cast on it, it regains 2d6 hit points. It disappears if it is reduced to 0 hit points or after 1 hour. You can dismiss it early as an action.

When you create the cannon, you determine its appearance and whether it has legs. You also decide which type it is, choosing from the options on the Eldritch Cannons table. On each of your turns, you can take a bonus action to cause the cannon to activate if you are within 60 feet of it. As part of the same bonus action, you can direct the cannon to walk or climb up to 15 feet to an unoccupied space, provided it has legs.

The thing is, it disappears after an hour, and then you create a new cannon if you want to use the feature again. So going from zero (killed the cannon) to full (summoned a new one) is a pain in the ass. 

Appreciate you looking into it tho! :)

Quote from taliesin_qd >>

The thing is, it disappears after an hour, and then you create a new cannon if you want to use the feature again. So going from zero (killed the cannon) to full (summoned a new one) is a pain in the ass. 

 That is... an excellent point.

I keep trying to see a way to reset it... and you're right. It's literally no other way than single dot up or down. Which, if you had one that has a max of 55, and took 20 damage - so you resummon later... sure, it's a few seconds of clicking "+" repeatedly... but there should just be a manual way of adjusting the "HP" of it by just entering the number needed (whether damage or health). That seems like an oversight.