Software & Electronics Design

Wireless UART

With the wireless UART / RS-232 link it is possible to connect a PIC / AVR / uP wirelessly to a PC. On the PC, the wireless UART is a standard COM port which you can use in your software, just like any other COM port. Any data written to the COM port will be wirelessly transmitted to the receiver PCB. There it is available for the receiving PIC / AVR / uP. Any response data is send back to the PC in the same way and can be read from the COM port by the software.

The wireless UART uses the license free 433 MHz band and has an outdoor range of up to 300 meter. Actual values can differ, depending on local conditions. Indoor range is generally more than enough to have the modules anywhere in the house and still have reliable communication.

The data communication is semi-duplex or half-duplex (see Wikipedia). Max data packet which can be transmitted at once, is 80 bytes. After writing 80 bytes to one of the modules, 180 msec is needed for all data to be transmitted. Smaller packets of course need less time. See calculation formula in the manual.

Wireless UART Layout


The system consists of 2 modules, both containing a RFM12 wireless chip and a PIC microcontroller to handle the data transmissions. The top module has a 4 pins header which outputs the UART signals directly. This module needs +5V. At +3V3 the module will not work. The bottom module has an FTDI USB chip to handle the communication with the PC. It takes its supply voltage from the USB port.

Wireless UART


Click here to download the pdf manual.
Wireless UART Manual page 1


Click here to download a small test program. With this program you can send some data over the wireless UART and check if the link is working (Tx & Rx LED's will blink shortly). If you have a PIC / AVR / uP which "answers" back, you can read the answer too.
Wireless UART Test Program


The wireless sensor modules & wireless UART are sold in our e-shop