About
One engineer, working close to the metal.
Demux Labs is the practice of a single embedded engineer working close to the metal: firmware, reverse engineering, embedded networking, and the security of all three.
That engineer is Juan Carlos Jiménez Caballero, known to most colleagues as JC. Firmware and reverse engineering since 2014, almost entirely for teams in the US: an early stretch in London, then remote work from Alicante, Spain.
The work tends to arrive in one of three shapes. A team has hardware and needs someone who has shipped this class of product before. A team has inherited a device nobody understands (no source, no supplier, no documentation) and needs it understood. Or a team has shipped something and now needs to know how badly it would break under someone determined. All three are welcome.
Connected products are a large part of this, but they are an application area rather than the speciality. The interesting problems are usually the same whether or not the device ever talks to a network.
Being one person is a deliberate constraint. It means fewer simultaneous clients, no handover to a junior after the sales call, and an honest answer when a project needs a capability I do not have.
Terms
How engagements work
Consulting is charged at an hourly rate, invoiced monthly. Longer projects can be retained at an agreed monthly capacity instead.
Demux Labs works with clients across time zones. On-site visits for bring-up, workshops, or factory work are available. Travel, time, and expenses are billed to the client.
Source, schematics, keys, documentation, and tooling are yours. No proprietary runtime, no licence tied to me, no lock-in.
Every engagement produces documentation your team can act on after it ends. That is the point of hiring an outsider.
Working knowledge
Need me to hit the ground running?
Languages
- C
- C++
- Python
Targets
- ARM Cortex-M
- AVR & MSP430
- Espressif / ESP32
- Raspberry Pi
Runtimes
- Bare metal
- FreeRTOS
- Linux
- Arduino
Buses & interfaces
- I²C, SPI, UART
- CAN & RS-485
- USB
- JTAG / SWD
- Modbus
- HTTP
Networking
- TCP/IP on constrained stacks
- TLS / mTLS
- BLE, Wi-Fi, 802.15.4
- MQTT & proprietary protocols
Reverse engineering
- IDA
- Firmware extraction
- Logic & protocol analysis
Security
- Secure boot & chain of trust
- Secure elements, TPM
- Key generation & provisioning
- Fault & side-channel awareness
Engineering
- Hardware-in-the-loop CI
- Static analysis
- Production test rigs
- Release & signing automation
This is a baseline, not a ceiling. Whatever hardware platform, runtime, protocol, or toolset a project actually needs, I will pick it up, just as everything above got picked up in the first place. What stays constant is fluency across the stack, from register-level firmware to the abstractions built on top of it.
Available for new work.
Remote, international, and usually booked a few weeks out.