Direct connection to the Raspberry pi via the LM75 logger  or via RS232 is all well and good but to make something truly portable across multiple operating systems USB is just so convenient.

The circuit above is designed to fit into the a USB thumb enclosure from New age enclosures.

The circuit uses an FT232R USB to serial converter, FTDI supports drivers for most operating systems including raspbian. The FT232R then communicates the the PIC12F683 via a bit banged Uart. the PIc also reads the LM75 every 30 seconds or so and sends the data via USB. the code can be downloaded USB Datalogger.c

The data stream can be seen in any terminal emulator set to 1200 Baud, 8 bits no parity and no handshaking. The schematic is shown below.

The bill of material on this project is

QTY  PART-REFS           VALUE              

---  ---------           -----              

Resistors

---------

1    R1                  10k                

1    R2                  200k               

Capacitors

----------

2    C1,C2               47p                

3    C3,C5,C7            100n               

1    C4                  4u7                

1    C6                  10n                

Integrated Circuits

-------------------

1    U1                  PIC12F683          

1    U2                  FT232R             

1    U3                  ADT75              

Diodes

------

2    D1,D2               SD103              

Miscellaneous

-------------

1    CN1                 USBCONN            

2    J1,J2               TERMINAL           

1    L1                  MI0805K400R-00