2/11/15
This week I continued GPS testing, got the RF communication working, and received the I2C memory chips in the mail (finally). I am still unable to read anything from the GPS by serial or I2C communication. I have tried several different serial communication programs such as Command Prompt, MiniGPS, PuTTY, and the Arduino IDE. For every test I get nothing. Not even garbage results, I just don’t get anything in terms of results. I am considering finding another GPS now, but first I would like to sit down with Professor Hedrick and/or Professor Spinelli to see if they can help me establish some sort of a connection. JP has also been working with GPS sensors for his project and I will talk to him this week as well. If I cannot any results from this Navigatron V2 sensor by the start of next week then I will order a different sensor and try and return this one if possible/necessary.
This week I was able to establish a connection between the transmitter and receiver. The components operate at 434 MHz and use amplitude shift keying (ASK) to communicate with each other. Below is an example of a transmitted and received byte of information.
I was finding a lot of problems with this method at first. Since the components use ASK, they are very susceptible to noise. There would be lots of moments when the received scan on the oscilloscope just look static. The plot above was after a few tries to get a clear scan of the received signal. The code I was using the transmit and receive was also unable to interrupt the received signal.
I found an Arduino library called Virtual Wire and adopted that for the project. Using the library I was successfully able to transmit and receive information. This is because Virtual Wire provides a lot of features for transmitting ASK information. It includes a lot of checksums for data verification. This allowed me to transmit and receive data because the Virtual Wire library was able to help filter out the noise and focus on the actual information transmitted. I had trouble at first using the Virtual Wire functions because they were setup with sending ‘char’ variables in mind and not integers, but this was soon fixed by converting integers into char variables.
In other news the I2C memory chips arrived today and I should be able to get those working soon. From what I have read they should be simple and easy to use, but we will see. My goals for next week are to: make a decision/progress with the GPS and integrate the memory chips.
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