Homework 3
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Temperature sensor hacking


In this one, we will test out the temperature sensor example code that comes with the SDK from NXP. The code is located in the following directory in your SDK directory tree:

SDK_2_16_100_FRDM-RW612/boards/frdmrw612/driver_examples/i2c/read_p3t1755_temp_value_transfer

Step 1: Build the temperature sensor code and flash it onto your board. It should print temperature readings to the serial port. Use minicom to read from the serial port. Confirm that the temperature sensor is working by heating up the sensor with your hand/thumb to make sure the temperature increases.

Step 2: Modify the wifi_httpsrv example from Homework 1 to display temperature readings on the webpage. Start with the cgi_example() function on line 147 of httpsrv_freertos.c.

A bit of background: in the days of yore, CGI (common gateway interface) was a mechanism that allowed HTTP servers to generate dynamic content by executing programs locally on the HTTP server. The program to generate the dynamic content could be written in any language you wanted (perl, C, java, whatever). CGI fell out of favor long ago because of its security risks---allowing anyone on the internet to directly execute a program on your webserver with basically no guardrails in place is a bad idea. However, it was/is favored for embedded systems because of its low resource overhead---you don't need a full-blown nodejs server to generate dynamic content.