|HP 15c LE low power anomalies|
Message #1 Posted by Nick_S on 29 Mar 2012, 3:08 a.m.
A power management bug in the 15c LE calculator has been reported, here are some anomalies that I experienced. I have been using one of these calculators regularly for the last 5 months and it has shown some strange behaviour, which seems to be at least partly related to power supply and battery issues.
There have been two occasions in the last couple of months when the memory got corrupted. On the first occasion the program memory had a couple of lines here and there swapped that I was able to sort out through editing, but last week I had to re-enter all my programs as the program memory had become filled with many lines of garbage.
In the last 24 hours, rather than displaying a blinking * low battery indicator, the display numbers just turned from black to light grey whenever a key was pressed. I had several occasions when insufficient registers were indicated (incorrectly) to run the solve or integrate functions. Only a total of 50 instead of 65 registers were shown with the g MEM function (having all the matrices A..E set to size 0,0), meaning that the available free registers now fell below the number required for solve or integrate. I could get the calculator to display a total of 65 registers and be able to again use the advanced functions simply by running a program that did some basic arithmetic. This morning I got the Pr Error message in the middle of running the integration function and the calculator had lost the contents of all memory.
In my experience, the calculator with its present firmware (checksum: ChE--FFFFh, 2011-04-15, C 2008 hP) cannot be reliably counted upon to preserve the contents of memory. I would recommend committing all important programs to disk/paper as an external backup. I have each program I use entered in a text file on my computer together with test examples so that I can rapidly enter the programs and check that the code works as intended.
I like using calculator a lot, so I hope a firmware solution can be found by HP (or the user community). As things stand, I now always run a couple of test cases to check the integrity of a program before using it for important work.
Edited: 29 Mar 2012, 8:42 a.m. after one or more responses were posted