Hire the Best GSM Developers

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Vishnu C.

Belgaum, India

$5/hr
4.7
41 jobs

I am an electronics and firmware developer with experience in PCB design, firmware development, prototyping and SMD assembly. My journey started with hand crafting single sided PCBs — giving me a strong practical foundation from the ground up. PCB Design: 2 and 4 layer PCB design in KiCad 8,Kicad 9(Soon migrating to Kicad 10) & EasyEDA(Standard & Pro version) . Former EagleCAD user Schematic to manufacturing ready layout Custom footprint creation Gerber, drill, pick and place and BOM files Full submission support for JLCPCB(PCB & PCBA) and similar manufacturers Assembly & Prototyping: SMD soldering — 1206-0402 passives, QFN, TSSOP (except BGA) Through hole soldering Small batch prototype assembly Component procurement support Firmware & Connectivity: Microcontrollers — ESP32, ESP8266, Arduino, AVR, 8051 Cellular — Quectel EC25 & SIMCom SIM7672 with MQTT SSL/TLS Wireless — LoRa, WiFi, Bluetooth, GSM GPS — Ublox & Quectel module integration Displays — OLED, TFT, capacitive touch Protocols — I2C, SPI, UART, MQTT SSL/TLS, HTTP REST Motor drivers, WS2812 LED arrays, power circuits GPS- Quectel L89, Ublox M10S Special - WS2812 Led Projects include: GPS trackers, GSM security systems, water level controllers, , line followers, obstacle detection robots, WS2812 LED arrays and various ESP32 and Arduino IoT devices. I am a full time freelancer committed to clear communication and timely delivery — working with hobbyists, startups and commercial clients alike. Feel free to reach out!

  • AVR Microcontroller
  • ESP32
  • Raspberry Pi
  • Microcontroller Programming
  • Arduino
  • Firmware
  • ESP8266
  • Eagle
  • PCB Design
  • Electronics
  • KiCad
  • Electronic Design
  • MQTT
  • Digital Electronics
  • Circuit Design
  • Hardware Troubleshooting
  • Embedded C
  • EasyEDA
Chirantan K.

Nashik, India

$10/hr
4.9
37 jobs

I am an electronics engineer with a decade of experience in schematic design, PCB layout, and firmware development. After founding a successful tech startup in 2010, I am now seeking to expand my reach through online platforms. My company specializes in the design and development of customized consumer and industrial electronics projects, offering state-of-the-art solutions and dedicated computer systems. Over the years, we have successfully designed various systems, including data loggers, data monitors, data acquisition systems, data processors, process controllers, and IoT solutions tailored to our clients' specific needs. Our expertise spans microcontrollers, microprocessors, FPGAs, SoCs, and System-on-Modules (SoMs). We are also proficient in wireless technologies such as XBee, BLE 4.0, BLE 5.0, GSM, and LoRa. Services we offer: 1. Component Engineering 2. Schematics and PCB design 3. Firmware development 4. Prototypes and Mass production 5. Vendor Co-ordination Deliverables we provide include: 1. PDF Documentation: Schematics, PCB artwork, and 3D views of the PCB. 2. Source Files: Schematics and PCB files in Altium format. 3. 3D STEP File: A detailed representation of the PCB. 4. Gerber Files: For manufacturing. 5. NC Drill Files: For precise drilling specifications. 6. Bill of Materials (BOM): Compiled from verified vendors and suppliers such as Mouser, Digi-Key, and JLC, ensuring reliability and consistency over time. 7. Firmware/Software: Including codes and sketches tailored to your specifications. 8. Prototypes and Mass Production: Comprehensive support from concept to production. We prioritize compatibility with leading vendors like Mouser, Digi-Key, LCSC, and JLCPCB in our BOMs, facilitating a comparative analysis of available components and expediting the prototyping and mass production processes. Additionally, we ensure that selected components are stable and widely available, mitigating concerns about obsolescence or stock shortages. I look forward to the opportunity to collaborate and contribute to your project’s success.

  • Internet of Things Solutions Design
  • Robotics
  • ESP32
  • Arduino
  • Raspberry Pi
  • PCB Design
  • Embedded C
  • Embedded System
  • Amplifiers & Filters
Nguyen Dinh B.

Hanoi, Vietnam

$25/hr
5.0
55 jobs

Hello! I’m Ben, a hardware and firmware expert with 8+ years of experience in designing hardware, programming embedded systems, and developing high-performance software solutions. My goal is to provide innovative, reliable, and high-performance solutions that meet your needs. What I Offer 1. End-to-End Embedded & Hardware Solutions - Advanced PCB Design & Hardware Development: Expertise in schematic capture, PCB layout, and multi-layer board design for reliable, high-performance, and manufacturable products. Experienced with KiCad, Altium, OrCAD, and Eagle. - High-Speed Design: Strong experience in 1–12 layer PCBs, including DDR3/DDR4/LDDR4, PCIe, USB (2.0/3.0/3.1/3.2), HDMI and 10/100/1000/10Gbase-T1 Ethernet. - Microcontrollers & SoMs: Firmware and hardware development for ARM Cortex-M3/M4 (STM32, ESP32, Nordic nRF52/53/91 series,...); custom boards for Raspberry Pi CM4/CM5, Orange Pi, iMX8, Jetson Nano/Xavier/Orin, RK3588/RK3588S, RK3568, RV1126, Allwinner, Zynq-7010, Zynq7020, XCZU9EG - Power & Hardware Integration: Experience in DC-DC, AC-DC, Buck, Boost, and Flyback converters, along with hardware design involving audio, RF modules, PA, LCD, filters, RFID, touch screens, and LVGL-based interfaces. - Prototype, Testing & Validation: Full support for board bring-up, debugging, validation planning, and functional testing to ensure hardware works reliably in real-world applications. - Manufacturing & Prototyping Support: Preparation of BOM, Gerber, and manufacturing-ready files, with hands-on support for prototype production and manufacturing through JLCPCB and PCBWAY. 2. Robust Firmware Development - Languages & Development: Strong embedded firmware development in C/C++, Python with experience using Visual Studio Code, STM32CubeIDE, Arduino IDE, ESP-IDF, and Segger. - Communication Protocols: Proficient in USB, UART, I2C, SPI, I2S, RS232, and RS485, enabling reliable communication across embedded systems and connected devices. - Wireless & Connected Systems: Experience with BLE, BLE Mesh, ZigBee, UWB, LoRa, NB-IoT, 4G LTE, Wifi, WiFi Mesh, and NFC for IoT and wireless product development. - Sensor: light sensor, CO, Smoke Sensor, Dust Sensor, Air Sensor, pH sensor, IMU sensor, Accelero, Gyro sensor,... - UI/UX for Embedded: Figma, TouchGFX, LVGL for STM32, ESP32, Raspberry Pi. - Motors Control: BLDC, Stepper, Servo, DC Motors - Robotics: Expertise in ROS/ROS2 for applications like AGV, AMR, 6-axis robots. Some of my product that I have designed and released to the market: - Home IP Camera: SoC-based design with DDR3 RAM, Ethernet/Wi-Fi streaming, CMOS image sensor, IR LED array, IR-cut control, USB, and MicroSD - Smart Home Products: Home Gateway with Ethernet, Wi-Fi, Zigbee, and TFT LCD; Smart Switch with capacitive touch, Zigbee, power metering, and AC load control - Tablet Mainboard: RK3399-based board with DDR3, eMMC, touch screen, LTE. - Smart Water Meter: BLE/Wi-Fi design with TI MCU. - Wearable Devices: Low-power wearable designs with wireless connectivity, sensors, and battery management - High-Performance ESC for Drones: Real-time motor control design for efficient and stable drone operation - Custom SBC with AI Module: Raspberry Pi-based SBC solutions with integrated AI capabilities And a lot of other products. With our experience and expertise, I’m confident I can provide tailored solutions to help you complete your project and release your product to the market . I look forward to the opportunity to work with you.

  • PCB Design
  • KiCad
  • Altium Designer
  • nRF52
  • STM32
  • ESP32
  • Raspberry Pi
  • FPGA
  • Hardware Design
  • EasyEDA
  • OrCAD
  • nRF52832
  • Arduino
  • LoRa
  • Embedded System
  • Firmware
  • Embedded Linux
  • Schematic
  • Bluetooth LE
  • WiFi
YUQIAN Y.

Beijing, China

$200/hr
5.0
4 jobs

When systems break under real-world constraints — unstable networks, missing documentation, mixed hardware — I step in to diagnose and fix them. I specialize in: • Systems integration (IoT, edge devices, multi-protocol environments) • Real-time streaming (WebRTC / RTSP / low-latency pipelines) • Performance & storage engineering (high-throughput, large-scale systems) • Distributed systems & Go backend (control-plane, metadata services, cluster coordination) Selected work: • Airport perimeter security platform Integrated fiber optic vibration sensors, IP cameras, alarms, and lighting into a unified real-time alert platform. → Received hands-on training from Fibersonics engineers on sensor physics and signal analysis — applied this to configure per-zone detection parameters, achieving near-zero missed detections with low false positives across outdoor conditions → Debugged and stabilized WebRTC/RTSP streaming through packet-capture analysis — no documentation available; resolved by reading ZLMediaKit source code and tracing protocol negotiation → Deployed and in active use • Offline mesh-based classroom system Built ESP32-C6 mesh network for student response collection in zero-WiFi environments. → Power-optimized to ~1 month battery life (4000mAh) in testing → Designed full stack: embedded firmware + desktop management + cloud analytics • Offline canteen management system Implemented custom TCP server on Android with a Windows C++ Qt client over direct ethernet. → Ensured data integrity for large transfers in a network-restricted environment with no external infrastructure → Deployed and in active use • Metadata control-plane for disaggregated database (major state-owned bank) Core developer of the Go-based metadata/control-plane service that enabled compute-storage separation on a Greenplum/PostgreSQL-based distributed database. → Centralized TB-scale metadata — transactions, sessions, locks, invalidation state — previously trapped inside local compute nodes → Built on FoundationDB (core KV backend), etcd (cluster coordination, leader election), and a custom RPC layer → Implemented session lifecycle, distributed locking, deadlock detection, and invalidation message pipeline • Disaggregated storage system (China Construction Bank) Core developer of the disaggregated storage module managing thousands of PBs across multi-cloud object storage (AWS S3, Alibaba Cloud, Huawei Cloud, Tencent Cloud) behind a ~1TB local cache. → Designed query-driven prefetching and segmented caching of hot data → Cold start ~20x slower than SSD; warm cache performance on par with SSD • Adaptive compression engine (YMatrix time-series database) Designed automode system that dynamically detects data characteristics across stream segments and selects optimal encoding chains (zigzag, simple8b, deltadelta, Gorilla2, lz4/zstd). → Deployed in production — patented encoding chain design Prior to the above, I spent 6 years as Lead Engineer at FreeWheel (a US media-tech company, acquired by Comcast), building Kubernetes-based microservices platforms and cutting fault localization time from over a day to under a minute using Istio service mesh and distributed tracing. Before that, I was a Technical Expert at Alibaba Cloud, where I extended a database proxy to support the PostgreSQL protocol (read/write splitting, failover reconnection) and built a stability engineering system for RDS PostgreSQL that kept the service running through 2021 Double 11 — one of the world's highest-traffic e-commerce events. I've diagnosed production issues across Go, C++, and distributed systems — including a Golang memory leak traced through Prometheus metrics to a misconfigured HTTP client, and C++ performance bottlenecks in deployed systems. My approach: correlate monitoring data with business operations to narrow scope before touching the code. I've published source-level analysis of Prometheus internals on InfoQ. Domain experience with counter-drone detection systems — participated in field testing and evaluation of RF detection and optical tracking platforms, with firsthand understanding of operational scenarios, detection requirements, and alert workflow needs. If you're dealing with: • unstable integrations • streaming issues (WebRTC / RTSP) • hardware + software systems not working together • performance problems in production —I can help you find and fix the root cause. Tech stack: Systems Integration Engineer | Edge AI, Video, Embedded & Distributed Systems

  • C++
  • Golang
  • PostgreSQL
  • Kubernetes
  • Java
  • Greenplum
  • C
  • AWS Development
David P.

Hanoi, Vietnam

$20/hr
5.0
22 jobs

Hi, I'm David. I help turn complex electronic concepts into dependable, production-ready products. With over 5 years of practical experience, I support clients through the full development cycle, from initial design to functional prototypes and manufacturing handoff. My focus is on building efficient, scalable, and cost-conscious hardware systems that perform reliably in real-world conditions. 1. What I Deliver: Embedded Systems & Hardware Development - PCB Design & Hardware Engineering: Circuit design, multi-layer PCB layout, component selection, impedance tuning, compact design, and cost optimization. Emphasis on IPC standards, signal integrity, EMI/EMC mitigation, and thermal considerations. - High-Speed & Complex Systems: Hands-on work with DDR, HDMI, MIPI (CSI/DSI), PCIe Gen1/2, along with SoC and FPGA-based prototyping. - Embedded Platforms: STM32N6, STM32H7/STM32H5, STM32F7/STM32F1/F3/F4, ESP32/ESP8266, Nordic nRF52 series, ARM Cortex-A systems, Raspberry Pi (CM4/CM5), Zynq-7000. - Power & Mixed-Signal Design: Switching regulators (Buck, Boost, Flyback), LDOs, battery systems, motor control (BLDC, stepper, servo, DC), and analog/digital integration, PoE, LLC. - Manufacturing Readiness: BOM preparation, Gerber generation, and design adjustments to streamline production and reduce costs. - Tools: Altium Designer, KiCad, LTspice, Proteus, MATLAB/Simulink . 2. Firmware & Software Development - Programming: C, C++, Embedded C, Python (for automation and validation). - System Development: Linux-based platforms, MCU firmware, RTOS (FreeRTOS), power optimization, bootloaders, OTA updates, and debugging. - Connectivity & IoT: WiFi, BLE, LoRa, Zigbee, GSM/LTE/NB-IoT/5G, GPS, RFID, NFC. - Communication Interfaces: UART, I2C, SPI, I2S, RS232, RS485, CAN, Modbus RTU/TCP, USB, Ethernet. - User Interface: LVGL-driven GUIs, TFT/OLED displays, and touch interfaces. 3. Development Process & Collaboration - Product Lifecycle Support: Concept → prototyping → validation → production handover. - Workflow & Management: Organized development using Git, Jira, and structured documentation with clear milestones. - Global Collaboration: Experience working across US, EU, and Asia time zones with consistent communication. - Troubleshooting: Strong capability in diagnosing and resolving both hardware and firmware issues. 4. Why Choose Me? - Unified Skillset: Combined hardware and firmware capabilities help minimize back-and-forth and speed up delivery. - Practical Engineering Approach: Designs are built with real-world constraints in mind — not just theory. - Efficiency-Oriented: Focus on reducing unnecessary costs while maintaining performance and reliability. - Clear & Responsive Communication: Regular updates, well-documented progress, and quick feedback. Looking to bring your idea into a functional, well-engineered product? Feel free to reach out. I’d be glad to discuss your project !!!

  • ESP32
  • KiCad
  • Linux
  • Altium Designer
  • STM32
  • Raspberry Pi
  • LoRa
  • Arduino
  • Microcontroller Programming
  • Hardware Design
  • Bluetooth LE
  • PCB Design
  • Touchscreen
  • WiFi
  • NFC
Anh N.

Hanoi, Vietnam

$17/hr
5.0
7 jobs

Hello, I’m an Embedded Firmware & Hardware Engineer with solid experience in developing IoT, automation, and wireless systems. I specialize in low-level firmware design, communication protocol integration, and user interface development, combined with practical hardware design and testing. My goal is to deliver robust, efficient, and production-ready solutions tailored to your needs. 🔧 Key Experience ► Embedded firmware design: Bare-metal & RTOS (C/C++) ► Board bring-up, debugging & validation ► Hardware schematic & PCB design (analog, digital, mixed-signal) ► Parts selection, BoM creation & manufacturing file preparation ► Power supply design: DC-DC (buck/boost), linear regulators ► Documentation & source code management 🛠 Microcontrollers & Platforms ► STM32 (Cortex-M0+/M3/M4/M7) ► ESP32, ESP8266 ► nRF52 series ► Holtek, PY32, MG82F6D17 ► Arduino, Raspberry Pi 🔗 Interface Protocols ► UART, SPI, I2C, RS485 ► QUADSPI, ADC, DAC ► USB 2.0, USB 3.0 📡 Wireless & Communication ► Wi-Fi, BLE (Bluetooth Low Energy) ► Ethernet, 4G/LTE ► LoRa, LoRa Mesh, LoRaWAN ► NFC, RF Modules, Power Amplifiers 📺 Displays & Modules ► UI development with LVGL on TFT Touchscreens ► LCD, OLED Displays ► Sensor integration (temperature, GPS, ultrasonic, laser) ⚡ Hardware & PCB Design ► Multi-layer PCB design (1–6 layers) ► Impedance-controlled routing, high-speed interfaces ► Mixed-signal circuit design (ADC/DAC, filters, amplifiers) ► Motor control: BLDC, Stepper, Servo, DC ► RF & antenna design basics 🏆 What I Deliver ✔️ Reliable embedded firmware (C/C++) with efficient drivers & protocols ✔️ Robust, manufacturable hardware designs ✔️ End-to-end IoT & embedded solutions (from prototype to production) 🤝 Let’s work together to turn your embedded system ideas into scalable, reliable products.

  • Hardware Design
  • Altium Designer
  • PCB Design
  • Firmware
  • Raspberry Pi
  • Microcontroller Programming
  • Internet of Things
  • LoRa
  • ESP32
  • Bluetooth
  • Touchscreen
  • Embedded Linux
  • C
  • C++
  • nRF52
  • Power Electronics
  • NFC

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What does a GSM developer do?

A gsm developer builds software that controls cellular modems to send and receive text messages over mobile networks. This role focuses on implementing the standardized AT command set to bridge application logic with hardware devices. You write code that manages serial connections, encodes message payloads, and parses raw responses from the network. Your work enables applications to communicate directly with the cellular infrastructure without relying on third-party web APIs.

  • You implement control flows for GSM modems by sending specific AT commands over serial or USB connections. This involves writing parsers that interpret device responses and handle state changes such as network registration or signal loss. You manage the low-level communication protocol to ensure the host application correctly interprets modem status codes and error messages.
  • You build SMS functionality that encodes text or PDU data formats for transmission through the cellular gateway. Your code constructs the necessary command sequences to submit messages and listens for delivery reports or incoming texts. You handle character set conversions and message segmentation to support various languages and long-form content across different device capabilities.
  • You integrate modem drivers into larger software systems to create reliable bridges between business logic and hardware. This requires testing compatibility with various 3GPP specifications and adjusting command sets for specific modem manufacturers. You document supported commands and troubleshooting steps to help other engineers maintain the connection stability and resolve hardware-specific issues.

How to hire a GSM developer on Upwork

Step 1: Post a job

Define your need for AT command integration and SMS logic to attract qualified candidates. The Job Post Generator powered by Uma™, Upwork's Mindful AI drafts a post after you describe your needs in a few sentences. You can write a new post, update a saved draft, or reuse an existing post.

  • Specify the modem hardware interface, such as serial or USB, and the required ETSI or 3GPP AT command sets.
  • List deliverables like PDU encoding logic, CMGS transmission flows, and error handling for network state changes.
  • Clarify if the role involves bridging host application logic with modem drivers or building standalone SMS gateways.

Step 2: Evaluate candidates

Look for portfolios that demonstrate direct experience with GSM modem control and response parsing. Uma can run instant video interviews and build shortlists with side-by-side comparisons to help you assess technical fit.

  • Check for code samples that show robust parsing of AT command responses and handling of unsolicited result codes.
  • Verify experience with SMS payload encoding, including both text mode and PDU format implementation details.
  • Review documentation they authored that maps specific device behaviors to standard GSM 07.05 or 07.07 specifications.

Step 3: Interview your top choices

Discuss their approach to modem compatibility and troubleshooting communication failures. Interviews can be scheduled and conducted within Upwork Messages with an immediate transcript and summary after each one.

  • Ask how they debug issues when a modem fails to enter the correct command mode over a serial connection.
  • Request examples of how they validated SMS delivery success against varying network conditions and device types.
  • Explore their method for testing edge cases, such as SIM card errors or unexpected network registration states.

Step 4: Agree on scope and begin work

Set clear milestones for modem integration, SMS functionality, and validation against AT standards. Use Upwork Messages and the contract workroom for communication and project management, plus identity verification, payment protection, hourly tracking, and project funds for security.

  • Define the specific AT commands the module must support and the expected response formats for each.
  • Establish testing criteria that require successful send and receive operations across multiple modem models.
  • Require a runbook that documents configuration steps, supported modes, and troubleshooting procedures for future maintenance.

Upwork is not affiliated with and does not sponsor or endorse any of the tools or services discussed in this article. These tools and services are provided only as potential options, and each reader and company should take the time needed to adequately analyze and determine the tools or services that would best fit their specific needs and situation.

The rates and information provided in this article are based on current data and industry sources available at the time of publication. Freelance rates can vary depending on factors such as experience, location, project scope, and market conditions. Readers are encouraged to conduct their own research to confirm current rates and trends, as this information may change over time.

How much does hiring a GSM developer cost?

$500-$1,500 per project is a typical range for focused GSM developer work. Final pricing depends on scope, technical complexity, required integrations, source-material quality, revision needs, and the freelancer's experience level.

AT command scripting

$500-$1,200/project

Entry-level to mid-level
  • Automated AT command sequences for modem control
  • Parsed response data from serial interface tests
  • Basic troubleshooting steps for common errors

SMS gateway integration

$1,200-$2,500/project

Mid-level
  • Code for sending and receiving SMS via PDU encoding
  • Logic for processing incoming message events
  • Validation of text and binary message flows

Modem driver development

$2,500-$4,500/project

Mid-level to senior-level
  • Custom client code for USB or serial modem connection
  • Bridge between host application and modem hardware
  • Documentation of supported 3GPP AT commands

Cellular network validation

$4,500-$7,000/project

Senior-level
  • Automated tests for network registration and signal states
  • Analysis of modem behavior across different carriers
  • Patches for device-specific command incompatibilities

Full stack GSM solution

$7,000-$12,000/project

Expert-level
  • End-to-end architecture for cellular data and SMS
  • Secure endpoints for external application access
  • Complete runbook for deployment and maintenance

Frequently asked questions

Is hiring a GSM developer worth it?

For most businesses, yes: hiring a GSM developer is worthwhile. These specialists build direct connections between your software and cellular networks using standard AT commands. They handle the complex logic required to send and receive SMS messages through GSM modems without relying on third-party cloud APIs.

How do I evaluate GSM developer candidates?

Look for candidates who demonstrate specific experience with AT command sets and PDU encoding for SMS transmission. Ask them to explain how they parse modem responses and handle error codes during network state changes, as this reveals their ability to manage real-world connectivity issues.

What tools does a GSM developer use?

A GSM developer uses serial or USB connections to interface with cellular modems and relies on terminal tools to inspect AT command exchanges. They also apply ETSI or 3GPP specifications to ensure the code complies with standard GSM protocols.

Can a GSM developer integrate SMS functionality into my app?

Yes, a GSM developer writes code that bridges your application logic with a GSM modem to send and receive text messages. They implement the necessary data formats and command flows to make this hardware integration work reliably.