CODEWITHSUNDEEP
embeddedpicradio-transmission
Sirakhil
Sirakhil

Reputation: 83

Plot a graph of Time vs RSSI for a 433Mhz RF ASK Receiver

Hi Im using the following RF module

http://www.apogeekits.com/rf_receiver_module_rx433.htm

on an embedded board with the PIC16F628A. Sadly, I realized that the signal strength was in analog form and couldn't get any ideas to get the RSSI reading off the pin because well my PIC is digital DUH!.

My basic idea was

  1. To get the RSSI value from my Receiver
  2. Send it to the PIC
  3. Link the PIC to a PC via RS232
  4. Plot a graph of time vs RSSI of the receiver (so I can make out how close my TX is to my RX)

I thought it was bloody brilliant at first but ive hit a dead end here. Any ideas on getting the RSSI data to my PC from this receiver would be nice.

Upvotes: 0

Views: 1294

Answers (2)

Clifford
Clifford

Reputation: 93564

The simplest thing to do is obviously to use a more appropriate microcontroller - one with an ADC! There are many (most), including PICs (though that wouldn't be my first choice).

Attaching an external SPI or I2C ADC might be a bit tedious since having no SPI or I2C on your part, you'd have to bit-bash it. If you do that, use an SPI part - its simpler. Your sample rate will suffer and may end-up being a bit jittery if you are not careful.

Another solution is to use a voltage controlled PWM, then use the timer input capture to time the pulse width. That will give you good regularity and potentially good resolution. You can get a chip (example) to do that, or grow your own. That last option requires a triangle wave input as well as the measured (control) voltage, but on the same site...

In a similar vein, you could use a low frequency VCO (example) and use the output to clock one of the timers, then using a second timer periodically sampling the first and reset it. The count will relate to the voltage, though not necessarily a linear relationship, linearisation could be none on the PIC or at the receiving PC - I'd go for the latter - your micro will suck at arithmetic (performance wise) - even integer arithmetic, especially if it involves division.

Upvotes: 0

TJD
TJD

Reputation: 11896

You can get a PIC that has an integrated ADC for sampling the analog signal. Or, you can use an external ADC chip to do the conversion. You would connect that to your PIC using SPI or I2C.

Upvotes: 0

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