Hardware and firmware engineer
I am Muhammad Sufian. Clients come to me with a product idea, a board that does not work, or firmware that keeps failing in the field. I take it through schematic, layout, code, bench testing, and the cloud side when there is one. Below are 19 projects in embedded firmware, PCB design, RF and IoT. Each one has a case study and the design files on GitHub.
A few highlights first, then all 19 projects grouped by type. Every card links to the code, the files and a short case study.
PCB · IoT
A battery Wi-Fi lock board for vending cabinets, moved from a 2.4 GHz module to a dual band one with a 40 µA idle floor. Seven lock channels on four AA cells that ride out a 1.9 A latch pulse, and the client's firmware runs unchanged.
PCB · Firmware
A 16 mm round four layer board for a Bluetooth button sold as jewellery. 3.47 µA idle measured on a PPK2, months on a 45 mAh cell, and a Gerber check of my own that caught a short the design rule check had passed.
PCB · IoT
System design and a 70 by 20 mm board for a gauge that sits under an LPG cylinder. The battery set the reporting schedule, about thirteen months on one pouch cell. A netlist review before fab found twelve problems, two of them blockers. Under NDA.
Firmware · PCB
A small speaker that plays speech from the client's cloud and follows a daily timetable when the internet drops. Custom ESP32-S3 board, ESP-IDF firmware, and two lwIP fixes that took streaming from 17 KB/s to 200 KB/s. Under NDA.
Firmware · Cloud
A pool and spa hub in the field kept rebooting. I reviewed the code, found three separate reboot loops, and built a presence backend on AWS so the dashboard stopped showing dead hubs as online. Twelve reboots an hour became one. Under NDA.
Firmware
Ten ESP32-C5 boards in one box that listen for Wi-Fi and Bluetooth and log to SD in WiGLE format. One transport API over ESP-NOW or an I2C backplane. 31,183 records in a bench run with none lost. Under NDA.
RF · PCB
A carrier board for TI's AWR2944 radar chip. Four transmit and four receive antennas laid out on Rogers laminate, power brought up in the right order in hardware, CAN FD and Ethernet to the car.
RF · PCB
A 10 watt GaN amplifier for the 5 to 6 GHz band. Matching tuned in SystemVue, stability checked across the whole band, harmonics filtered on the output, and a machined heatsink. Delivered with gerbers, BOM and a report.
RF · PCB
An amplifier around a packaged S band transistor. Matched on the substrate the client actually orders, k and mu checked across the band, and a low pass filter on the output that keeps the second and third harmonics down.
RF · PCB
A 24 GHz rangefinder board plus a written study on why the stock module fell short on range. Path budget, antenna gain, LNA noise and the IF chain, then the smallest set of changes that fixes it.
RF · PCB
A switch board that routes any antenna to any radio chain, or any port on a test bench to the analyser. Sized for the client's enclosure with the control lines on a header, instead of one evaluation board per channel.
RF · PCB
A UWB receiver that works out which direction a signal comes from. A small logic circuit drives three RF switches from just two pins, so the host processor keeps its spare pins.
Firmware · PCB · RF
A coin cell tag for the European 866 MHz band. The PIC sleeps well under a microamp, a FET cuts power to the antenna between beacons, and the dipole is tuned on the real board, not in a simulator.
PCB
An STM32H7 flight controller that boots the standard Pixhawk firmware with no code changes. Two IMUs sit on their own quiet ground island so the calibration holds under motor load, and the barometer is vented.
PCB · IoT
A battery Wi-Fi lock board for vending cabinets, moved from a 2.4 GHz module to a dual band one with a 40 µA idle floor. Seven lock channels on four AA cells that ride out a 1.9 A latch pulse, and the client's firmware runs unchanged.
PCB · Firmware
A 16 mm round four layer board for a Bluetooth button sold as jewellery. 3.47 µA idle measured on a PPK2, months on a 45 mAh cell, and a Gerber check of my own that caught a short the design rule check had passed.
PCB · IoT
System design and a 70 by 20 mm board for a gauge that sits under an LPG cylinder. The battery set the reporting schedule, about thirteen months on one pouch cell. A netlist review before fab found twelve problems, two of them blockers. Under NDA.
Firmware
Firmware written straight to the registers, no HAL and no RTOS. It samples at 2 million samples a second, works out I and Q of a 29 kHz signal on the chip, and streams the result to a PC over USB a thousand times a second.
Firmware
ESP32-S3 firmware that adds card and QR payment to a vending machine that only takes coins. It presses the keys the machine already has, so the safety logic is never touched. USB and RS-232 from one build.
Firmware · Product
A finished product. Two sensors under a prayer mat count each sujood, an ESP32-S2 tracks the rakat, and four LEDs show progress before it resets. Firmware, enclosure CAD, and a test tool that mirrors the state machine.
Firmware · PCB
A small speaker that plays speech from the client's cloud and follows a daily timetable when the internet drops. Custom ESP32-S3 board, ESP-IDF firmware, and two lwIP fixes that took streaming from 17 KB/s to 200 KB/s. Under NDA.
Firmware · Cloud
A pool and spa hub in the field kept rebooting. I reviewed the code, found three separate reboot loops, and built a presence backend on AWS so the dashboard stopped showing dead hubs as online. Twelve reboots an hour became one. Under NDA.
Firmware
Ten ESP32-C5 boards in one box that listen for Wi-Fi and Bluetooth and log to SD in WiGLE format. One transport API over ESP-NOW or an I2C backplane. 31,183 records in a bench run with none lost. Under NDA.
Cloud · Firmware
A vending platform from the board to the bank. DA16200 firmware in C, AWS IoT and Lambda behind it, Stripe Connect for the payouts, and a web console for operators. Scan a QR, pay, and the slot opens in seconds.
Industrial · Firmware
A Raspberry Pi supervisor for a bottle filling line that never reached its PLC. I read the ladder rung by rung, fixed the Modbus address map, and the line kept its panel, its VFD loop and its safety logic.
PCB design, embedded firmware development, RF and antenna design, and IoT cloud backends. Usually two or three of them on the same job.
01
Schematic and layout in EasyEDA Pro or Altium, two to six layers, mixed signal and RF. You get gerbers, a BOM with LCSC part numbers and pick and place, so JLCPCB can build it without questions. I check the fab files with my own scripts before anyone pays for a board.
02
ESP32 on ESP-IDF, STM32 bare metal or HAL, PIC, Nordic on Zephyr. I write it in C, test it on the bench with a logic analyser and a PPK2, and hand over builds with hashes so every unit can be traced back to its source.
03
Power amplifiers from S band to 6 GHz, radar boards at 24 and 77 GHz, UWB, sub GHz tags. Matching, stability, harmonics, antenna keep outs, and tuning on the real substrate rather than a vendor reference.
04
AWS IoT Core, Lambda and MQTT for the device side of a product. Code and board reviews when something already built keeps failing, with the risks ranked and a fixed price plan you can buy one part at a time.
I work as a freelance embedded systems engineer. Most of my clients are small companies building their first hardware product, or teams with a board or firmware already in the field that is not behaving.
I like the parts of a job where the analog, the RF and the code all have to agree. I measure before I decide, I write down what was proven and what was not, and I deliver files the next engineer can pick up without calling me.
Some of the work here is under NDA. For those projects the case study is the version the client agreed to, with names and files left out.
Schematics, layouts, firmware and the written case studies live in the GitHub repositories. Open any project above, read the case study first, then the files.