R-OSHI V5 PCB Prototype

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Subject: Request for Custom PCB Design, Prototype Development & Assembly – R-OSHI V5 Audio Spectrum Visualizer

I am developing a custom electronic project called R-OSHI – Real-Time Audio Spectrum Visualizer, and I am looking for an experienced electronics/PCB engineering team to convert our current prototype wiring into a professional custom PCB and fully tested working prototype.

I am attaching our current R-OSHI V5 wiring diagram for your technical reference.

The project is based on an ESP32 + SmartElex MSGEQ7 + 74AHCT125 level shifter + WS2812B addressable LEDs.

1. Project objective

R-OSHI receives a stereo line-level audio signal from an AVR, DAC, CD player or other line-level audio source.

The SmartElex MSGEQ7 module analyzes the audio into seven frequency bands. The ESP32 reads the spectrum information and drives two independent WS2812B LED columns, producing a real-time visual representation of the music.

The final system will control:

240 WS2812B LEDs total

* Column 1: 120 LEDs
* Column 2: 120 LEDs
* 5 V WS2812B
* 60 LEDs/meter
* Two independent data outputs

2. Proposed electronics

The present architecture is:

Stereo line-level audio → SmartElex MSGEQ7 → ESP32 → 74AHCT125 → WS2812B LEDs

Main components:

* ESP32 30-pin development module
* SmartElex MSGEQ7 7-band audio analyzer module
* 74AHCT125 quad 5 V logic buffer/level shifter
* 240 × WS2812B, 5 V
* External 5 V / 40 A SMPS
* Two 1000 µF electrolytic capacitors at the LED power inputs
* 100 nF ceramic decoupling capacitor for 74AHCT125
* 330 Ω series resistors on the two LED data outputs
* 20 kΩ / 20 kΩ voltage divider for the MSGEQ7 analog output
* Appropriate protection, connectors, fusing and power distribution

3. Current ESP32 pin assignment

Our current proposed pin assignment is:

ESP32 Function
GPIO27 MSGEQ7 RESET
GPIO26 MSGEQ7 STROBE
GPIO34 MSGEQ7 analog OUT through 20 kΩ / 20 kΩ divider
GPIO13 LED Column 1 data
GPIO14 LED Column 2 data

GPIO13 and GPIO14 feed the two channels of the 74AHCT125.

4. 74AHCT125

We specifically require a 74AHCT125, preferably DIP-14 for the prototype unless you recommend an equivalent suitable SMD implementation for the final PCB.

Current assignment:

74AHCT125 Function
Pin 1 – 1OE GND
Pin 2 – 1A ESP32 GPIO13
Pin 3 – 1Y Column 1 LED DATA through 330 Ω
Pin 4 – 2OE GND
Pin 5 – 2A ESP32 GPIO14
Pin 6 – 2Y Column 2 LED DATA through 330 Ω
Pin 7 GND
Pin 14 +5 V

Unused channels should be terminated correctly according to the manufacturer’s recommendations.

5. Power architecture

The LED system will use an external:

5 V / 40 A SMPS

The high-current LED power will not pass through the ESP32 PCB traces or breadboard.

We want proper power distribution with:

* Separate high-current feeds to Column 1 and Column 2
* Appropriate PCB copper width/plane or external power terminals
* Common ground between ESP32, MSGEQ7, level shifter and LED system
* Separate protection for the two LED branches
* Approximately 5 A branch fusing
* 1000 µF bulk capacitor at each LED-column input
* Proper decoupling of the logic circuitry

The ESP32 will be powered independently through USB-C.

6. Audio input

The input is line-level stereo audio only.

We do not want speaker-level output connected to the MSGEQ7.

The PCB should preferably provide convenient:

* Left audio input
* Right audio input
* Audio ground

using RCA connectors or another suitable connector arrangement that you recommend.

7. Very important – SmartElex MSGEQ7 module verification

We would like your engineer to verify the actual SmartElex MSGEQ7 module electrically before finalizing the PCB.

We will provide photographs of the actual module that we are using.

In particular, please verify:

* Audio input terminals
* +5 V and GND
* MSGEQ7 analog OUT
* RESET connection
* STROBE connection
* Ground routing
* Connector/pad arrangement on the actual SmartElex PCB

We do not want the PCB manufactured simply by assuming a generic MSGEQ7 breakout pinout.

If necessary, please trace the actual module and confirm the connections before PCB fabrication.

8. PCB requirement

We would like your team to develop a custom controller PCB, preferably integrating:

* ESP32 interface
* MSGEQ7 interface
* 74AHCT125 level shifting
* ADC voltage divider
* LED data outputs
* Power distribution/interface
* Protection components
* Screw terminals/connectors
* Status/test points
* Proper decoupling
* Mounting holes

The extremely high-current LED wiring can remain external to the controller PCB if you consider that electrically and mechanically preferable.

We are more interested in a robust and serviceable design than putting everything onto one PCB unnecessarily.

9. Prototype requirement

Our immediate requirement is:

One completely assembled and tested working prototype.

We would like you to handle:

1. Schematic review
2. Electrical verification
3. PCB design
4. PCB layout
5. Design-rule checking
6. BOM preparation
7. Component procurement
8. PCB fabrication
9. PCB assembly
10. ESP32 firmware/programming
11. Initial power-up testing
12. MSGEQ7 audio testing
13. WS2812B output testing
14. Two-column simultaneous testing
15. Full-load testing
16. Final functional verification
17. Shipment of the completed prototype

10. Documentation required

Along with the assembled prototype, we would like to receive the complete engineering documentation:

* Schematic
* PCB layout/source file
* Gerber files
* BOM
* Pick-and-place files, if applicable
* Component specifications
* Firmware/source code
* Programming procedure
* Test procedure
* Final PCB revision number
* Assembly drawings

We would prefer the design to be developed in KiCad or EasyEDA, but we are open to your recommendation.

11. Future production

The first requirement is only one prototype.

If the prototype performs correctly, we may subsequently require additional units.

Therefore, please design the PCB with future small-batch production in mind and advise us whether you recommend:

* THT
* SMD
* Mixed SMD/THT

for the final production version.

12. What we would like from you

Please provide a quotation separately for:

A. Engineering/design charges

B. PCB fabrication

C. Component procurement

D. PCB assembly

E. Firmware/programming

F. Prototype testing

G. Complete assembled prototype

H. Shipping to Bilaspur, Chhattisgarh, India

Please also provide the estimated development time from receiving the required information to delivery of the tested prototype.

13. Important engineering expectation

The attached R-OSHI V5 drawing represents our current architecture and intended functionality, but we would like your electronics engineer to review it critically.

If you identify any electrical, PCB-layout, power-distribution, signal-integrity, ADC, grounding, EMI, thermal or WS2812B-related issue, please propose the correction before fabrication.

We are specifically looking for an engineering partner who can take the project from:

Prototype concept → verified schematic → PCB → assembled hardware → tested working R-OSHI unit.

We can provide the actual ESP32 board, SmartElex MSGEQ7 module photographs, LED specifications, existing wiring diagram and other project information required for engineering.

Please let us know whether your can undertake this project and provide a quotation.

Thank you.

Regards,
Dr. Raman Jogi
Bilaspur, Chhattisgarh, India
Project: R-OSHI – Real-Time Audio Spectrum Visualizer