Here is a pure mystery. I would like to have some explanation, if you have any!
On my Panda, I am reading temp sensor (TMP38) using analog input. It works well.
On my Panda, I have added a SD-Card reader, soldered by myself. It works well.
But as soon as I use both (for data-logging my temp), the temp sensor measures wrong temperatures like -40°C!
The temp sensor becomes wrong right after I call this in my code:
PersistentStorage ps = new PersistentStorage(“SD”);
I don’t even have to mount the file system to have the temperature getting wrong!
I thought it was due to a magnetic field generated by SD-Card / SD-card reader, but I checked my HMC6352 Compass and it works well with SD-card running… So I think it is not an issue a mag field.
I have verified :
=> input voltage at temp sensor input is OK. 5V
=> It is not a bug in AnalogIn reading. The output voltage of temp sensor is abnormally low.
Strange isn’t it?