Silicon Chip – June 2019

siliconchip.com.au Australia’s electronics magazine June 2019 93

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Fig.5 shows how to connect the

RA-02 to an Arduino Uno while Fig.6

shows the connections for a Micro-

mite. The configuration shown in

Fig.5 suits Sandeep Mistry’s library;

you might need to change it if you’re

using a different library.

In both circuits, the RA-02 module

receives its 3.3V supply from a 3.3V

LDO regulator, fed from the micro’s 5V

output. Although the current drawn by

the RA-02 is significantly lower than

that of the E32-TTL-100, it still draws

enough when transmitting to cause

problems if powered directly from the

micro module’s 3.3V output.

With this arrangement, we made

two Arduinos communicate via RA-

02 modules using Sandeep Mistry’s

library. However, this does not work if

you replace one of the RA-02 modules

with an E32-TTL-100 module, even

when both have been set to operate at

434MHz. So you need to use the same

type of LoRa module at either end.

Our example sketch is named

“SCLoRaSend_and_Receive.ino” and

this is available for free downloading

from the Silicon chip website.

We have also written a similar Mi-

cromite MMBasic program, called

“RA02 LoRa module checkout prog.

bas”, available on the Silicon chip

website. Using this, we were able

to get two Micromites to communi-

cate via RA-02 modules, and also ex-

change data between an Arduino and

a Micromite using two identical RA-

02 modules.

com/item//32467389771.html).

The adaptor cables are sold togeth-

er with 800MHz whip antennas fitted

with an SMA plug, for around $1 each

(plus $7 delivery to Australia!). After

discarding the useless (to us) 800MHz

whip, we used these adaptor cables to

connect one of the ‘loaded whip’ an-

tennas mentioned earlier to the RA-02

modules. Problem solved!

boards with the RA-02 module already
soldered to them (www.aliexpress.
com/item//32824507293.html).
We didn’t have any luck finding a
suitable 434MHz whip antenna al-
ready fitted with a cable ending in a
U.FL-P plug. But we were able to get
hold of a couple of adaptor cables with
an SMA socket on one end and a U.FL-
P plug on the other (www.aliexpress.

Fig.6: connection diagram for the RA-02

module to a Micromite. Again we’re using

an LM1117 to power the RA-02 because it

might draw more current than the Micromite’s

onboard regulator could possibly supply.

Fig.5: connecting the RA-02 module to

an Arduino.