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Standalone Signal Analyzer (I2C Type Signal-Meter) for uBITX #1 - Create and use with Character LCD

Standalone Signal Analyzer (I2C Type Signal-Meter) for uBITX
Create and use with Character LCD

This idea was discussed in the uBITX group (
I used a separate Arduino to expand the limited I/O. The material needed is Arduino Nano, two resistors and one capacitor, Estimated cost is less than $3.
Now, since it is the initial version, only the received signal is measured, but if it is applied a little, output power and SWR can be measured together.
1.Create and use with Character LCD
2.For Nextion LCD
3.Nextion LCD Advanced

1.Standalone Signal Analyzer (I2C Type Signal-Meter) ?
You do not need to enter the ADC value in uBITX Manager
Please check 'Use S-Meter' only. Signal Meter has increased precision.
The valid signal is measured from 3 and is expressed as +10 dB.

You can then apply the Power Meter and SWR Meter.
Available for both Character LCD and Nextion LCD (include TJC LCD)

2.Parts List
  Arduino Nano  x1
  Resistor          x2  (10k ~ 20k)
  Capcaitor        x1  (0.01uF ~ 0.03uF)

You can use any resistors around 10k~20k. However, the two values of resistors must be the same. I used an 20k resistor
A capacitor of 0.01 uF will be the easiest to obtain. 0.01uF (10nF -> marking 103)
Look around you now. Maybe the resistors and Capacitor will be easily available to make
It is very simple and probably has a fairly high success rate. It's too simple, right?
I will introduce several versions. You can make what you like. You can also create your own version.

3.1 DIP Parts Version #1
Prepare two 20K resistors and a 10nF capacitor as shown below.

Tie three ends together.

Finish !!!

You can connect as follows

3.2 DIP Parts Version #2 - Attach parts directly to Arduino Nano
I used it for an intro video uploaded on YouTube

Put one resistor into the GND Hole and the A7 Hole. Pass from bottom to top as shown.

Solder on top. We will put parts in + 5Volt, so leave a little gap.


Bend another resistor as shown below.

Place the resistor in the + 5Volt hole on the top. See the figure below

Bend the other end of the resistor and connect it to A7.

Connect one more capacitor to A7.

3.3 SMD Parts Version
I often make a few of these things and use them
It can be used conveniently when you create and work with several versions.

Parts List
18k Resistor x 2
0.011 Capacitor x1
2.54pith Pin x 6

Cut Pin

Connect the capacitor to the pin.

Connect the Resistors to the pin.

Connect pins to the other side.

4.Upload Firmware to I2C Signal Meter

Connect Signal Sensor to uBItX

5.uBITX Firmware Update
uBITX CEC Firmware supports I2C Meter from Version 1.097
Upload to version 1.097 or later.
Version 1.097 will be released in less than a week

In uBITX Firmware, for I2C meter, the file name is followed by _S

uBITX firmware CEC Version FileName rule
prefix   : UBITX_CEC_
Version  : Vxxxx (ex: V1.097)
LCD Type : _XXX  (ex: 16x02 Parallel = 16P, 20x04 Parallel = 20P, 20x04 I2C = 20I, Nextion LCD = NX)
Signal Meter Type (Option) : none : Analaog Meter using A7 PIN
                             _S   : I2C Signal Meter using I2C Port

UBITX_CEC_Vxxxxx_16P.hex    : It is the LCD equipped with uBITX. Default LCD, 16x02 Parallel LCD
UBITX_CEC_Vxxxxx_16P_S.hex  : _16P with I2C Meter

UBITX_CEC_Vxxxxx_16I.hex    : 16x02 I2C LCD
UBITX_CEC_Vxxxxx_16I_S.hex  : _16I with I2C Meter

UBITX_CEC_Vxxxxx_20P.hex    : 20x04 Parallel LCD
UBITX_CEC_Vxxxxx_20P_S.hex  : _20P with I2C Meter

UBITX_CEC_Vxxxxx_20I.hex    : 20x04 I2C LCD
UBITX_CEC_Vxxxxx_20I_S.hex  : _20I with I2C Meter

UBITX_CEC_Vxxxxx_16D.hex    : 16x02 I2C Dual LCD
UBITX_CEC_Vxxxxx_16D_S.hex  : _16D with I2C Meter

UBITX_CEC_Vxxxxx_NX.hex     : Nextion LCD
UBITX_CEC_Vxxxxx_NX_S.hex   : _NX with I2C Meter

6. Example of use in Character LCD
You only need to check S.Meter in uBITX Manager.
If the ADC Level entry is 0, enter 1 because an error occurs. For I2C S-Meter, do not use Level value.

When I2C LCD is used, I2C wires should be connected in parallel

The source code and pre-compiled Hexfile will complete this document and will be released together.

Please see the video below for an example.


  1. Great stuff! building this with tjc nextion. Thanks again Ian, please send me the beta code (Hex)

    1. tom How are you
      OK. I can not send .HEX because I am out now.
      I'll send it to your email address within 10 hours.

      Thank you

  2. Replies
    1. vu2kyz

      Version 1.097 .hex file was released shortly. I will source code upload to github after publishing the document about source codes.
      if you want source code now, I can send source code by email.

      Ian KD8CEC

  3. Hi Ian,

    It is pure AC coming from vol HI. How does the measurement work in principle? It is AC coming from VOL HI to Arduino?

    I have got a couple of those nano's. I'm holding my breath as I wait for the code.

    Kai, OH3WE

    1. Kai
      Yes, that's right. It is the VOL_HI connection of uBITX. Maybe you are connected to your uBITX volume.
      I was annoyed to separate uBITX from the case for this. So I connected the line to the Volume. (VOL_HI is connected to Volume)

      thought of a few things.
      The first attempt was to display the highest value after the FFT measurement.
      The second was to use the largest of the amplitude differences of all AC values.

      Both methods are not problematic because the source code measures the ADC and performs the FFT continuously.
      I am using the second method now. I adjusted my instrument to show a more accurate signal-meter.
      I wanted to make the S-Meter a bit more useful than the ornaments that make my eyes delightful.

      Ian KD8CEC

    2. Today I tried to upload 1.097 file to Raduino. It went well, but Nextion display still says V.1095.
      Did it two times, no go! Still 1.095.

      I prepared an extra Nano for the standalone S-meter but I'm afraid I can't carry on now.

      I also used UBitx manager and tried to check the box "use S-meter" but after that it asks me to set the sliders....why?

      I am a bit confused now.

      Kai OH3WE

  4. I had to upgrade the Nextion LCD in order to get it to show right version.
    Slill looking for the HEX for the DSP Arduino.
    Difficult to find.

    Kai OH3WE


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