Product firmware
ESP32 (Arduino, PlatformIO, and ESP-IDF), AVR/Arduino, STM32/GD32, and RP2040. The goal is behaviour that still works after a reboot, a bad network, and a firmware update.
Electrical engineer
Firmware for devices that leave the bench.
I write the software inside ESP32, STM32, and Raspberry Pi products: sensors, radios, displays, and the path from the board to a dashboard. Nearly seven years of that work, for teams that need a field unit.
100%Job Success Score
PlusTop Rated Plus
26Upwork jobs
2,275Hours on Upwork
7 yrsHands-on embedded
01 / Selected work
What I have actually shipped
01
Sayapatri contactless payment terminal
Card tap → ESP32 → Wi-Fi or GSM → payment flow
Two ESP32 payment terminals. One takes the amount from a phone over BLE and joins shop Wi-Fi. The other uses a keypad, a battery, and a cellular modem.
02
Addify 3D printer
Touch panel → STM32 TouchGFX → PID thermal control
The Addify printer’s thermal UI on STM32: TouchGFX screens from the supplied designs, PNG assets, PID on the heater, and a developer mode for the display and touch.
03
Remote hive monitor
Weight, climate, GPS, solar → ESP32 → MQTT → ThingsBoard
A field node for a hive: weight, temperature and humidity, GPS, and battery or solar voltage, reported to ThingsBoard. A cellular modem is part of the unit.
04
Touchscreen data logger
Sensors → ESP32-S3 → LVGL panel → log
ESP32-S3 logger for 4.3 inch and 7 inch panels. It takes temperature and pressure over serial and BLE, stores the log, and can print or plot it.
05
Clinical cart kiosk
QR on Pi → UART → ESP32-S3 → ST7701 vitals UI
A Raspberry Pi reads a QR code and passes the identifier over UART to an ESP32-S3, which shows patient vitals on an RGB LCD.
06
Perfume dispenser
Button → Nayax MDB → Raspberry Pi → relay
A Raspberry Pi perfume dispenser. A Nayax reader takes a card over MDB, and the Pi pulses one of five relays only after the payment is approved.
02 / Teams
Where this work has been done
03 / Services
Where I am useful
Radios and field setup
BLE provisioning (including Nordic UART-style command protocols), Wi-Fi captive portals, ESP-NOW, and cellular: SIMCom A7670 / LilyGo T-Call, SMS, PPP, and a 4G hotspot.
Device to cloud
MQTT and HTTPS into ThingsBoard, Azure IoT Hub, and HiveMQ. Credentials in NVS, a queue when the link drops, and a way back into setup mode when the network is wrong.
04 / Clients
Feedback from finished jobs
“Working with Roshan was an absolute pleasure from start to finish. He exceeded every expectation — not only delivering exceptional programming and design work,…”
“Roshan did the work very quickly, was great and easy to communicate with, and performed great work. I will definitely contract with him again.”
“Roshan did an incredible job with our quick project. We needed it quick due to a deadline and they completed it in time and worked perfectly. Would recommend.”
“Roshan is very knowledgeable and understanding of our needs. He has stayed close to his midnights for testing and worked with our team. Highly recommend!!!!”
“I worked with Roshan on coding my custom PCB, and his expertise was exceptional. He created a virtual setup for testing, configured buttons and lights with…”
“Great working with Roshan, exceptionally talented on Arduino and IoT projects.”
“Was very helpful in the coding of the project. Very fast at finishing a code prototype and then furthering into the final code. Clear communications so I knew…”
“Roshan simply is on another level. His professionalism and willingness to help have no comparison. He is extremely knowledgeable in coding and electrical…”
“Very hard working and skilled esp32 firmware/software developer”
“Roshan was very helpful. He immediately jumped into the project and met ALL the requirements. He is very smart and went above and beyond. He is also…”