You are currently viewing S21RC SSPA Controller Hardware Rev 3.0.2

S21RC SSPA Controller Hardware Rev 3.0.2

[Project in progress, DO NOT MAKE PCB UNTILL TESTED]
[PCB, Schematic, and microcontroller codes released under MIT license by S21RC. You are free to use the material for personal/commercial use as it is or modify if needed as per the condition stated in the license], in simple term, software should contain the same copyright/license file and attribution. HMI display should have the “info” screen with all information and the Splash screen.

UPDATE: 22 JAN 2024
PCB REV 3.0.2 fixed missing ground and 2 short on i2c line.
CODE: (in progress.)
Function Block:

UPDATE 5 July 2023:
Rev3.0.1 BOM, CPL and Gerber uploaded.

UPDATE: During the test found some error and some improvement areas. New layout in progress.
Changes made:
1. CAT (CI-V) function added.
2. Pullup resistors added (error found during test – PCF8574 unable to drive ULN2803 without pullup)
3. External protection trigger IN is now routed through optocoupler.
4. BTS4141N replaced with TPS22810

1. Display function works ok
2. Setting save works ok.
3. Hardware protection for high input and swr tested ok.
4. Software protection works ok,
5. all temp sensor works ok.
6. Relay driver: Failed, need pullup resistors.
7. BIAS control Failed – BTS4141n might be fake.
8. All interrupt works ok.

After making the basic controller v1 which only had few peripherals and used through hole components and cheap Arduino Nano I decided to make another version with more options and future expandability. The Controller Rev2.0 was designed with Arduino Mega for the higher count of I/Os, but that never left the design table as I was hungry for more speed/power and expandability options. Born the Rev 3.0 utilizing Teensy 4.1 Microcontroller board which runs at a huge 600MHz speed (NXP iMXRT1062 chip with ARM Cortex M7 core).

Except the headers and few parts, all other components are SMD to save space. 1206 packages (cap, res, diode etc) has been used for easy home soldering.

1. 600MHz MCU
2. Highspeed comparator (LMV339) for monitoring high SWR/Power
3. Same PCB can be used for both high side switch and low side switch LPF boards (The final IC need to be selected as per your LPF type)
4. WiFi application with a ESP32 Wroom module (Optional)
5. Band Decoder (BCD and Voltage)
6. PTT input, PTT relay control.
7. 8 LPF channel for supporting future 4m.
8. Voltage and Current monitor.
9. Rotary band switch (optional)
10. Onboard CAN Bus controller for common PSU
11. 3 directional bridge/ SWR bridge input (Amp in, Amp out, LPF out)
12. Digital and 2nos NTC Temperature sensor options.
13. Protection Trigger out for external protection board
14. Board size (134x84mm) is same as Nextion 5″ display and can sit behind the display.
15. 2 25/31 KHz PWM out for Cooling fan.
16. OPT1 header has I2C, SPI and few I/O which can be used for more functionality or for a future daughter card (how about a 4×4 antenna switcher, or a sequencer, or….).
17. Can be used with 5/7/10 inch Nextion HMI display.

The display UI will be based on previous V2.0 UI with additional setup and features page for accommodating the new peripherals and options.
Or you can write your own code for this hardware.

Will be updated here.


BOM for Rev 3.0.1

PCB Gerber:
Download LDMOS SSPA Controller Rev3.0.1 (ZIP file contains the RS-274X Gerber files, and BOM & CPL files for the SMD components)

PIN Layout: Rev 3.0.1/2 Pinout

Schematic: OUTPUTS
Schematic: Antenna Power and SWR circuit
Schematic: LPF SWR circuit

17 May 2023: Components are soldered. Still waiting for few parts to arrive, but I can start coding now [Rev 3.0].

Apart from countless hours (and lots of coffee) to design the circuit, testing, coding thousands of line etc (In addition to my full time work) – I also had to order every component from of-shore for my experiment. As I do not sell KIT – there is no return except my own happiness.

If you like my work and wish to use it – you may show your appreciation and support my effort by a small donation. This is completely optional and has no effect on the support I try to provide over email/chat/Github. 73, S21RC

This Post Has 19 Comments

  1. Probir VU2BQF

    Hope you are Back

    1. s21rc

      Hello OM Probir, Yes I am back to Dhaka and resumed this project. New code uploaded – Basic functions working – now doing CIV implimentation.

    2. PROBIR

      Great you resumed your project …closely checking the status ONCE i see all working fine I will order the PCB Thanks


    BTW, could you please provide me the part # of LCD Display

    1. Fazlay

      You can use any 5″, 7″ Nextion Display (800×480 pixel). My test version is a 5″ Nextion Enhanced (NX8048K050).


    Great feedback. Yes, time to download the Gerber. To my wish list if the Power readout can be 2killowatt – that will be awesome

    1. Fazlay

      Yes, the new UI has enough space to show 4 digit.

    2. kg5qqw

      who are you using to make the pcb

      1. s21rc

        Hi OM, I use JLCPCB to make the PCB. Thanks, S21RC


    Hi Rabby,

    Just got involved in my MQTH work and could not keep a track . Is 3.0 hardware is tested or the package is yet to come. I need to order quite a no. of PCBs and wandering I can place order for 3.0 boards too. kindly update me the present status — i know you are equally busy with your MQTH work

    1. s21rc

      Hello Probir ji,
      Found some problem during the test, corrected it. The final layout will be ready by tomorrow I hope. You can order PCB then. Thanks, S21RC

      1. s21rc

        Hello Prabir, I have uploaded the updated Gerber/BOM and CPL. I have also ordered few boards from JLC assembled (only the SMD components). You may use the gerber to order PCB if needed. Thanks, S21RC

  5. Dana VE3DS

    Rabby I am interested also

  6. Denis

    Please share a schematich diagram

  7. López Cesar

    I wish to receive information

  8. Probir

    S21RC SSPA Controller Hardware Rev 3.0 PCB looks nice. Did you get a chance to work on this further.

    1. Fazlay

      Hi Probir ji, there was an IC package type error in the board, still waiting for the corrected version.

  9. Nicolas VE2NNX

    hello my friend, excellent work again, looking forward your test on rev3 board and you approuval that everything is OK to order mine 😉
    to bad you used pin 9 of the teensy 4.1, it is reseved for frequency mesurement, so you can implement auto sense band select feature. check the link
    if you did make more than 1 prototype board and you have one loose, i am ready to buy one direct from you… let me know

    1. Rabby

      Hi Nicolas,
      with Teensy4.1 you can use the frequency measurement using any/all FlexPWM pins, unfortunately the spare pins (26-27,32) left for future features do not support it.

      btw, additional circuitry is needed for bringning the RF to TTL level, and also may need some divider to measures upto 10m.

      I will let you know the result, and update this page with more info as progress. Thanks, 73, S21RC

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