SyncStim ESP32 Firmware and Optional PCB Design

@Mahihassi

As an accomplished electrical engineer and firmware developer with a strong background in embedded systems and PCB design, I assure you that handling the SyncStim ESP32 project will be well within my capabilities. My skills extend across your project's requirements including familiarity with ESP32 (ESP-IDF or Arduino-ESP32) and I2S audio, expertise in deterministic sub-10 us timing with usage such as MCPWM and RMT or timer ISR, sound knowledge of H-bridge and constant-current analog and oscilloscope proficiency among others that will be critical to the success of this project. Moreover, my mastery of KiCad and EasyEDA for PCB design positions me to deliver on the optional aspect of your project. From schematic to BOM finalization, firmware development, and timing planning, calibration, electrode-contact monitoring, fault handling all through to equipment safety compliance - I'll handle each milestone meticulously. Building experimental DIY electronics is a personal passion for me that aligns perfectly with this project’s maker culture. In the past I have designed some really intricate electronic systems with exacting specifications like the SyncStim project but within educational constraints. This combination of passion and experience makes me uniquely suited to deliver not just safe but reliable products that perfectly fulfill their intended use.

@macroenergy

As an electrical engineer with a strong background in analog design, power electronics, and embedded systems, I possess the ideal skill set for your SyncStim ESP32 firmware and PCB design project. I've had extensive experience with projects involving constant-current power sources, H-bridge control, and precise timing – all of which are core requirements for your devkit. My proficiency in ESP32 (ESP-IDF or Arduino-ESP32) and experience with I2S audio routing also make me a great fit. I've developed embedded system applications for several Microcontrollers including STM32 and Atmel that make me confident in my ability to complete the task accurately and effectively. In previous roles, I have successfully designed and implemented RF transmitters, receivers, implemented motor drives, and worked on AC/DC converters that adds values to my ability to deliver a precise and effective firmware for SyncStim. As you mentioned the relevance of oscilloscope verification, my experience with Orcad Simulation will allow me to ensure that the resulting pulse train, audio burst, stimulus intervals, cadence - everything down to the timing precision required is met. Lastly yet importantly, my familiarity with EDA tools such as KiCad and EasyEDA assures high-quality schematic designs during the optional PCB phase. Having worked on similar projects both personal and professionally over the years enhances my hold over using these tools proficiently.

@engrusmanfaiz

Your architecture is technically solid for this type of experimental timing-sensitive device, and the key challenge here is deterministic pulse generation with safe current limiting while maintaining precise synchronization between I2S audio and stimulation timing. I have experience with ESP32 low-level peripherals (timers, MCPWM/RMT, ISR-driven timing), audio pipelines, embedded power electronics, and oscilloscope-based validation workflows. For this project, I would likely use hardware-timed peripherals rather than software delays to guarantee sub-10µs timing stability and repeatable biphasic pulse generation. I can support the full firmware workflow including timing architecture review, pulse-generation logic, audio synchronization, safety/fault handling, electrode-detection monitoring, calibration routines, and oscilloscope verification support. Optional PCB design in KiCad/EasyEDA and prototype bring-up can also be handled in a second phase if required.

@SPARKtechBD

Real-time working experience in ESP32 to build any kind of digital device. You can see my more detail in the bellow... Since 2003 I am working in Digital Electronic. So more than 18 years of experience in Electronics. Arduino NANO/UNO/MEGA, ESP32 and Raspberry PI to build a digital device to read sensor data and send it to the web server, motor control, control relay switches and LEDs. More than 5(five) years of experience in Arduino design and build. If you want an excellent and error-free project delivery, then send a message to me, please. Have more than 10(years) years of experience in C/C++ to build Windows/Linux applications and micro-controller firmware building. If you want a good job delivery, then send a message to me, please. Since 1995 I have been working on Analog and Digital Electronics to build any kind of device. I have build lots of devices. So more than 20 years of experience on Electronics. Including power supply design. Any kinds of schematic and PCB design. Expert PCB design in EasyEDA Pro IDE.

@tshibsamuel477

Hi there, I’ve carefully read your SyncStim project description, and I can help develop the ESP32 firmware with precise I2S audio timing, biphasic pulse generation, LED cue control, logging, calibration, and safety fault handling. I’m Samuel Tshibangu, a mechatronics engineer with hands-on experience in ESP32 firmware, I2S audio, timer-based control, H-bridge driving, current sensing, SD logging, oscilloscope validation, and battery-powered embedded systems. I can work with ESP-IDF or Arduino-ESP32 and use deterministic timing methods such as MCPWM, RMT, or hardware timers to meet the sub-10 µs timing requirements. I can support the milestone-based workflow: design/timing review, firmware implementation, oscilloscope-verified pulse/audio behavior, electrode detach handling, and optional KiCad/EasyEDA PCB support if needed. Feel free to send me the schematic/BOM and timing details, and I can start right away. Best regards, Samuel Tshibangu

@shadabkhan92

Done similar tasks Doing this also, https://www.freelancer.com/projects/embedded-systems/Sensor-based-Stress-Management-Wrist/details As an experienced electrical engineer with a focus on embedded systems, I have the skills necessary to tackle your project. I've previously worked on projects that involved precise timing calibration and analog circuitry similar to what you require for the SyncStim firmware. In fact, I'm currently working on a device called the Stress Management Wristband which also involves configuring multiple sensors to deliver accurately timed stimuli while ensuring user safety. This experience demonstrates my ability to design for precise stimulus delivery within tight tolerances. I bring more than just technical capabilities to the table though. My proficiency extends beyond just delivering prototypes; I excel at managing full-scale production infrastructures. Your project aligns perfectly with my expertise in building autonomous agents and integrating them into complex workflows - such as pairing agentic AI with Odoo ERP and real-time sensor data analysis. This additional layer of knowledge ensures that the SyncStim project won't only be functional, but easy for you to implement and manage as well.

@TheElitePro

Hi, 1. I understand you need firmware where the primary challenge is deterministic timing: coordinating a 10 ms I2S audio burst, charge-balanced biphasic constant-current pulse train, while implementing safety monitoring and oscilloscope-verifiable behavior. 2. I have experience with ESP32 (Arduino), real-time embedded systems, I2S audio, motor/driver control, timer-driven signal generation, and hardware validation using oscilloscopes and logic analyzers. My focus is on timing-critical firmware that behaves predictably under load. 3. My approach: a) Review schematic/BOM and validate signal chain b) Build timing architecture using ESP32 hardware peripherals rather than software delays c) Implement I2S audio playback d) Generate biphasic pulse trains with enforced phase timing, polarity reversal, and net-zero charge balance 4. Deliverables: * Arduino firmware source code * Build instructions and documentation * Collaboration for Oscilloscope validation 5. Optional Phase: I can also support PCB design (KiCad) and prototype bring-up if required. 6. I appreciate the emphasis on verification. My goal would be to deliver firmware with required timing. 7. I am a preferred freelancer with 5 star rating and repeat customers, so you can count on me. Regards, Visha

@usmanbashir12100

Hi, I have the necessary experience in ESP-IDF, deterministic timing, and high-precision signal control to deliver the SyncStim firmware. I am comfortable with the hardware stack, specifically implementing charge-balanced biphasic pulses using the ESP32’s RMT/timer peripherals. Key Strengths: * Precision Timing: Sub-10 μ s μs pulse fidelity for the biphasic train, isolated from I2S audio jitter. Safety: Implementation of electrode-contact monitoring and hardware-level fault-handling. Validation: I am fully equipped to perform the required oscilloscope verification for all pulse and timing specs. I am ready to begin the design review immediately. What is your target timeline for this project?

@Ryan15222

Hi, Thank you for the detailed project description. Your project aligns well with my experience in embedded systems, electronics development, firmware architecture, timing-critical control systems, and hardware verification. I have worked on ESP32-based designs involving precise timing control, power electronics, data logging, sensor integration, and prototype development. For this project, I can support the following phases: • Review the existing BOM, schematic, and system architecture. • Verify timing requirements and firmware architecture. • Develop deterministic ESP32 firmware using ESP-IDF (preferred) or Arduino-ESP32. • Implement I2S audio playback through the MAX98357A. • Implement precisely timed H-bridge control using hardware peripherals (MCPWM, RMT, hardware timers, or equivalent). • Develop calibration, monitoring, fault detection, and logging functions. • Support oscilloscope-based validation of timing accuracy and waveform generation. • Prepare firmware documentation and test procedures. My proposed development approach: Phase 1 – Design Review Phase 2 – Firmware Development Phase 3 – Verification Optional Phase 4 – PCB Design

@volodymyrM05

Hi how are you doing well? I can develop the ESP32 firmware for your SyncStim devkit with a strong focus on timing fidelity, I2S audio control, biphasic pulse generation, safety fault handling, and oscilloscope-based verification. My team and I have solid experience with ESP32, ESP-IDF/Arduino-ESP32, I2S audio, deterministic timing using MCPWM/RMT/timer ISR, H-bridge control, constant-current stimulation circuits, SD logging, calibration, and prototype testing. My workflow will follow your milestones. First, I will review the BOM-based schematic, timing strategy, charge balance approach, current limit path, isolation assumptions, electrode monitoring, and safety shutoff logic. Then I will build firmware for the 200 ms cycle, 10 ms audio burst with ramping, configurable inter-stimulus interval with latency compensation, 3 biphasic pulses at 150 µs per phase and 1 ms onset spacing, LED cue, calibration, contact detection, fault halt, and logging. Finally, I will prepare test procedures for oscilloscope verification of timing, current, net DC, cadence, and electrode-detach behavior. One key question: do you prefer ESP-IDF for tighter timing control, or Arduino-ESP32 for faster maker-friendly development? I can complete this carefully within a milestone structure and would be glad to support the optional KiCad/EasyEDA PCB and prototype phase afterward.

@mobasherreza10

As an experienced embedded systems engineer, prototyper, and signal processing specialist, I hold the key skills necessary to complete your SyncStim firmware project with exceptional precision. I'm well-versed in ESP32 (ESP-IDF/Arduino) and the applicable I2S audio functionalities you require as well as having refined timing ability with MCPWM, RMT, and timer ISR techniques that your project calls for. Additionally, my mastery of H-bridge and constant current analog alongside the oscilloscope verification ensures accurate pulse generation of 3 pulses with phases' duration of 150μs each. When it comes to DIY experimental electronics like SyncStim, safety is paramount. My experience with power supply design using DC-DC boost converters and mains isolation makes me the perfect candidate to prepare your schematic to BOM while guaranteeing safety through my short but comprehensive safety review.