On September 22 (Monday night), the N.M.E. design group met to continue working on the ADC problem that occurred from Sunday’s lab testing. The ADC wasn’t giving us the right reference voltages. We observed the voltages coming from channels 0 & 1 of the MCP 3208. The problem was solved. We assumed it was the wiring of the ADC to the Prop. Chip. We then rewired the circuit. The wire from the MCP 3208 that went to the VDD pin was changed to 5 Volts. The Ref & VDD are the same now. Near the end of lab testing we encountered complications that involved using our conversion factor equation to display our Temperature correctly from the ADC. The spin language didn’t like displaying Decimals onto the VGA, so we decided to change our decimal value to a fraction and it resulted in displaying the correct room temperature. Before ending the night, we added a running timer (we used a counter) and temperature display to the propeller program (.spin).
On September 26, the N.M.E design group met to work on the project. Our main concern was (1) to replace the bent driveshaft and verify there were no additional internal damage to the car, (2) to configure the Analog to Digital (A2D) converter to output temperature readings in decimal values and (3) to write a code for the Parallax Datalogger so that it effectively records data outputs from the A2D. We encountered datalogger problems. We switched the modes on the datalogger from SPI to UART mode. Logged onto the Parallax website and downloaded Paul’s USB object from the Propeller Object Exchange. We had a problem displaying the values in the txt. File coming from the datalogger. The problem was the program didn't like displaying the integer values directly on the screen (ex. vga.dec(Temp)), it would only like to display strings. We did a trial and error process by coding into the program to record data into our logger every second. We noticed that it would display our string characters into a .txt file onto the USB, but would reject our integer values. Trying to display the integer values directly, would display several ASCII characters (ex !@#$%^&). We did this process several times to pinpoint why the program wasn't doing exactly what we were telling it to do. We knew that it would record our string characters in the .txt, so we wanted to try to figure out a way to convert our integer values to a string. So we solved the problem by calling the NumToString PUB from Paul's USB Object Library. As soon as we did that, the problem was solved.
[1] The picture below is of the new driveshaft for the R/C car[2] Picture below shows comparison of the new drive shaft (top) and the previous drive shaft (bottom). Note: the new driveshaft is thicker than previous drive shaft.
[3] Picture below shows our TV/VGA output of the current temperature and time counter within the code (.spin) of our program.
[4] Picture below shows proof that the running timer & temp. display are active and the timer is incrementing per 1 second.
Justin Rosario
N.M.E Design Team
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