Hi, I'm looking for an experienced PCB hardware designer + embedded firmware engineer for a challenging miniaturized IoT project. I need someone with hands-on experience in compact PCB layout, RF design, and ESP32 firmware development. Project Overview The goal is to design and build a fully functional ballpoint pen (it must still write) with completely hidden electronics inside that: Captures a photo when a capacitive button on the clip is pressed — target is a paper document at ~40cm distance, resolution sufficient to read 10pt text Automatically transmits the JPEG-compressed image over LTE-M Cat-M1 mobile network to an external endpoint (Telegram Bot or HTTPS server) Receives an SMS reply and displays it on a 0.42" OLED screen embedded in the clip, visible only from above Physical Enclosure Host pen: Faber-Castell Grip Plus Ball (ref. 140733) — available at ~4€ Triangular ABS resin body — RF transparent Usable inner diameter: ~12mm per flat face Usable interior length: ~105mm Original ballpoint refill must remain functional Proposed Component Stack I have done extensive technical analysis and propose this stack as a starting point for your assessment: No. 1 — ESP32-S3FH4R2 — ISP + JPEG compression + SPI master — QFN56, 7x7mm, JLCPCB ref. C3013940 No. 2 — OV5640 FPC mini module — 5MP DVP camera sensor — 9x9mm sensor + 24p FPC cable No. 3 — SIMCom SIM7090G — LTE-M Cat-M1 via UART AT commands — LCC, 14.8x12.8x2mm No. 4 — SSD1315 OLED 0.42" — SMS reply display on clip — I2C module, 12x11mm No. 5 — LiPo 401230 + PCM — 150mAh battery — 4x12x30mm No. 6 — TLV70033 — 3.3V LDO regulator — SOT-5, 1x1mm No. 7 — MCP73831 — 75mA LiPo charger via USB-C — SOT-23, 2x3mm No. 8 — AT42QT1010 — Capacitive touch button — SOT-23, 3x3mm No. 9 — FPC LTE antenna 60x10mm — LTE-M RF on plastic clip exterior — Flexible, IPX connector No. 10 — M7 pinhole lens f=3.6mm — 65° FOV optics at pen tip — diameter 3x8mm No. 11 — Nano-SIM push-push — Physical 4FF SIM slot — SMD connector, 12x15mm No. 12 — USB-C connector — Battery charging — SMD, 8x3mm Scope of Work PCB Hardware: Full schematic design in KiCad 4-layer rigid PCB layout, 10x90mm, fitting all components above RF ground plane optimization for SIM7090G + external FPC antenna Gerber + BOM + CPL files ready for JLCPCB SMT assembly service Manual assembly notes for camera FPC, LiPo, antenna, and OLED Embedded Firmware: Platform: ESP-IDF or Zephyr RTOS on ESP32-S3 Main flow: touch detection via AT42QT1010 GPIO interrupt, then OV5640 DVP frame capture, then JPEG compression, then UART to SIM7090G, then HTTPS/MQTT transmission, then SMS reception, then OLED display PSM Power Saving Mode between captures: target under 5µA sleep current Clean, documented code + USB-C flashing instructions What I Need From You Please reply with: Is this technically feasible as described? Would you change anything in the proposed stack? What is your quote for the full PCB design + firmware? What is your estimated timeline from kickoff to delivery of Gerber files + working firmware? Do you have prior experience with miniaturized enclosures, cylindrical PCB layouts, or LTE-M/NB-IoT designs? Please share relevant portfolio examples. Looking forward to hearing from you. Best regards, Alberto Blanco