Project layout

The project consists of five stages.

• Stage1: seven segment display array output
• Stage2: temperature sensor interface and temperature output
• Stage3: USB interface with computer
• Stage4: logging the USB data to the computer
• Stage5: Move the project from the development workspace to its own circuit

17 October 2006 - project started

My plan is to create a USB powered temperature display. I’m always wondering how warm it is when I’m sitting at my computer. This is my solution. I received samples of the TC77 temperature sensor from microchip last week (the 5 volt version). I decided on this one because it has very high resolution (13 bit) and is compatible with the SPI interface. This way I don’t have to take any measurements with an Analog to Digital port on the PIC, I just read data over the SPI interface. The only drawback is that the SOIC form is the biggest you can get it in and it’s hard to make a connection from it to the rest of your circuit. I soldered some wires onto the pins (really messy), I’m hoping it holds. I’m not too sure how much I will get done before my exams start but I plan on paying all my attention to this once the exams are over. This is a good start though

The TC77 temperature sensor diagram

My TC77 with wire soldered on (some not so neat connections), ipod nano in background for scale

24 October 2006 - Stage1 and Stage2 complete

The seven segment array code (Stage1) and the temperature sensor interface and operation (Stage2) is now complete. I’m using the EasyPIC3 from MikroElektronika to develop this project (it can be seen in the pictures below). I use MPLAB 7.40 to code. A detailed explanation is coming (in the next month or so), after I update my website to support more complex formatting. It cannot handle negative values yet but its in the pipeline.

The temperature display on the 7 segment array (its a hot day)

The project on the EasyPic3 development board from MikroElektronika

References

TC77 datasheet
Mikro Elektronika

Files

Assembly Source code up to Stage2