Wicked Wireless

Cheapo 433MHz.jpg

Since being grounded without the capability of operating EnOcean Sensors at 868MHz I've had to resort to other methods.

I had a cheapo 433.92MHz Transmitter and Receiver in the lab that had never been used so I hooked it up to see if it was a suitable for the task or not.

The maximum power limit I can use is 25mW and the transmitter has an output of 10mW.

One immediate limitation is that this configuration is single direction simplex communication link so there is no feed back loop back to the transmitter to confirm that the receiver received its messages.

 

I quickly kludged up a PSoC 4 projects using the CY8CKIT-049 42xx and had it sending 4800bps UART messages at the press of a button.

This consisted of using a SCB UART, Digital Input pin with Interrupt Support and a weeny ISR (Interrupt Service Routine).

 

I confirmed successful operation using a Tek oscilloscope.

Every time I pressed the button a test message was sent and confirmed on the oscilloscope.

 

The next step was to replace the direct wired connection with a wireless one.

This was accomplished by disconnecting the UART from the oscilloscope and connecting it to the transmitter.

The Tek oscilloscope was connected to the receiver.

 

The same tests were performed and the results were not promising.

The transmitter operated as planned but the receiver didn't behave as expected.

With the transmitter turned off, the digital output from the receiver was a whole bunch of junk.

With the transmitter turned on, the digital output from the receiver continually changed state at a much slower state without any activity from the transmitter.

Although I could write software at the receiver end to reject this unwanted junk it means that the microcontroller connected to the receiver could not go into a sleep mode to conserve energy.

I've noticed at the supplier website that they've upgraded the receiver. Maybe it was to address the issue that I was experiencing.

 

My next course of action is to test out RF Solutions ALPHA-TRX433S transceiver modules. Unlike the cheapo unit these modules can send in both directions and at a higher speed at 115.2 kbps.

Getting them to work is slightly more complex because they are SPI devices with a whole raft of configurable registers to manage.