Everybody seems to be abuzz with the idea that Opportunity's last transmission was "My battery is low and it's getting dark." Of course, that would be a human interpretation of some sort of diagnostics check. However, as far as I can tell, the only source for that information is a single tweet. According to the official Opportunity update log on sols 5108 to 5111, (June 7, 2018 - June 10, 2018):
The project team is listening each day during the expected fault window time with the Deep Space Network (DSN). No signal has been detected since the last normal communication on Sol 5111 (June 10, 2018). It is expected that we will not hear from the rover until the storm subsides over the rover site.
So the last transmission was some sort of "normal communication". According to a news post from the Opportunity team, there was a transmission on June 10 which included atmospheric opacity data , so there may be some truth to the "it's getting dark" part. But it doesn't say anything about battery level.
So that brings me to my question: What data was included in Opportunity's final transmission?