Firmata offered to upgrade itself, I accepted the latest from the list. it reported sum-check error.
This occurred on 3 separate days. 
I'm running 1.6.7 under Windows 10.
F.Y.I. it is perfectly ok updating anything less than the latest and greatest version of Firmata..
I just updated to Firmata V2.5.2 via the 'Library Manager' without a problem.
IDE V1.6.5, Windows 10 Pro 64-bit
I think the problem is that if you have a download of the library file that gets corrupted for some reason, maybe it only partially completes, the IDE just keeps trying to use that same screwed up downloaded file every time you try to install instead of deleting the file and downloading it over again. As OldSteve said, I can successfully install the library using Library Manager but I can also reproduce your issue by deleting the installed library from my sketchbook folder, corrupting the downloaded library zip file using a text editor, and then trying to install the library again using Library Manager.
To fix this issue you need to delete the downloaded library installation file. It is located at C:\Users{user name}\AppData\Local\Arduino15\staging\libraries\Firmata-2.5.3.zip. Then try to install Firmata again.
pert:
I think the problem is that if you have a download of the library file that gets corrupted for some reason, maybe it only partially completes, the IDE just keeps trying to use that same screwed up downloaded file every time you try to install instead of deleting the file and downloading it over again. As OldSteve said, I can successfully install the library using Library Manager but I can also reproduce your issue by deleting the installed library from my sketchbook folder, corrupting the downloaded library zip file using a text editor, and then trying to install the library again using Library Manager.To fix this issue you need to delete the downloaded library installation file. It is located at C:\Users{user name}\AppData\Local\Arduino15\staging\libraries\Firmata-2.5.3.zip. Then try to install Firmata again.
Good to know. Thanks pert. I'll try to remember this the next time I see the same issue.
Edit: I just noticed that you downloaded Firmata 2.5.3.
The latest available from my Library Manager is 2.5.2 - I feel ripped off. 
(Not a concern - I immediately went back to 2.4.3 anyway. I only upgraded to try to reproduce emmpeabeeHp's problem.)
I think the same problem happens with Boards Manager. I've been meaning to report the issue to the developers but haven't gotten around to it yet.
oH - I expected emails when I got replies - which didn't happen here - so I only found out I had replies by coming here for another reason -
DUH - sorry guys, thanks,
Tho it is midnight now, so I'll have a looksee in the AM after the birds have got up ;=} .
M
emmpeabeeHp:
oH - I expected emails when I got replies - which didn't happen here - so I only found out I had replies by coming here for another reason -
DUH - sorry guys, thanks,
Tho it is midnight now, so I'll have a looksee in the AM after the birds have got up ;=} .
M
I don't get email notifications automatically when I reply to a post either. I've got into the habit of manually clicking "Receive emails" every time now.
