4 layers54.6 × 57.1 mm
CM5 MINIMA
piecol/CM5_MINIMA_REV1
CM5 LoRaWAN carrier board in a compact, feature-filled footprint
98 parts63CERN-OHL-S-2.0
4 layers48.3 × 85.1 mm
Modem breakout
asgar-t/phone_projectcustom phone
- Size
- 48.3 × 85.1 mm
- Copper layers
- 4
- Thickness
- 1.54 mm
- Parts
- 77
- Nets
- 122
- Pads
- 374
- Tracks, vias
- 572, 301
- Pours
- 9
- Routed
- Yes
- KiCad
- KiCad 8.0 (file 20240108)
- Created
- 1 Nov 2025
- Updated
- 20 Dec 2025
Overview
Modem breakout is an open-source printed circuit board by asgar-t, from the asgar-t/phone_project repository on GitHub. It is a 4-layer board of 48.3 × 85.1 mm with 77 parts on 122 nets, routed with 572 tracks and 301 vias.
It is built around the EC25AFA-512-STD, TLV320AIC3104IRHBR and AMS1117-1.5, with the MIC29302WU, TXS0108EPWR and PTVS12VZ1USKYL among its other parts. Its parts include 39 capacitors, 15 resistors, 6 ICs, 6 diodes and 5 connectors. It belongs with the interfaces and adapters boards of this library.
Main components
10EC25AFA-512-STD
SMD,32x29mm20uA 3.3V~4.3V FDD-LTE I2C、USB、UART、PCM、SIM card SMD,32x29mm 2G/3G/4G/5G Modules ROHSQuectel2G/3G/4G/5G Modules
TLV320AIC3104IRHBR
HVQFN-32-EP(5x5)-40℃~+85℃ 1.1V~3.6V、1.525V~1.95V、2.7V~3.6V 8kHz~96kHz Encoder/decoder I2S、I2C HVQFN-32-EP(5x5) Audio Interface ICs ROHSTexas InstrumentsAudio Amplifiers
AMS1117-1.5
SOT-223-40℃~+125℃ 0.003%Vout 1 1.3V@(1A) 1.5V 18V 1A 5mA 60dB@(120Hz) Fixed Over Current Protection Positive SOT-223 Voltage Regulators - Linear, Low Drop Out (LDO) Regulators ROHSUMWVoltage Regulators - Linear, Low Drop Out (LDO) Regulators
MIC29302WU
TO-263-5-40℃~+125℃@(Tj) 1 26V 370mV@(3A) 37mA 3A 400uVrms、260uVrms Adjustable Over Current Protection、Over Temperature Protection、Reverse connection protection、Enable Positive TO-263-5 Voltage Regulators - Linear, Low Drop Out (LDO) Regulators ROHSTECH PUBLICVoltage Regulators - Linear, Low Drop Out (LDO) Regulators
TXS0108EPWR
UncategorisedUnknown maker
PTVS12VZ1USKYL
0603-40℃~+125℃ 10.5A 12V 13.3V 200nA 230W 29V 430pF TVS 0603 ESD and Surge Protection (TVS/ESD) ROHSNexperiaESD And Surge Protection (TVS/ESD)
DTC043ZEBTL
SOT-416FL-55℃~+150℃ 1 NPN (Pre-Biased) 1.1V 10 100mA 150mV 150mV@5mA,0.5mA 150mW 250MHz 4.7kΩ 500mV@100uA,5V 50V 80 NPN SOT-416FL Digital Transistors ROHSROHM SemiconductorDigital Transistors
AST-01532MR-R
-15mm 2.1kHz 2.1kHz~20kHz 300mW 32Ω 7.5mm - Speakers ROHSPUI Audio, Inc.Speakers
BSS138
SOT-23-55℃~+150℃ 1 N-channel 1.1Ω@10V、1.2Ω@4.5V 1.2V 1.7nC@10V 17.5pF 340mA 350mW 50V 6.5pF N-Channel SOT-23 MOSFETs ROHShongjiachengMOSFETs
CMA-4544PF-W
--44dB@±2dB 2.2kΩ 3V~10V 4.65mm 500uA 60dB 9.7mm Omnidirectional 插件,D=9.7mm Microphones ROHSCUIBuzzers
README
README.md📱 Phone Project
A custom embedded hardware project built around an STM32 microcontroller and Quectel EC25 modem.
The goal is to design, assemble, and program a complete phone system from the ground up — starting with hardware validation and moving toward a full integrated board.
🚀 Project Overview
Step 1 — Hardware Verification (current step)
- Bring-up of the main board and peripheral circuits
- Validate power rails, charging system, and USB interface
- Test modem communication (EC25) and antenna performance
- Ensure STM32 programming and serial communication are functional
Step 2 — Full System Integration
- Run the STM32 firmware with modem control and battery management
- Implement power sequencing and graceful shutdown logic
- Test full end-to-end operation (voice/data + MCU control)
- Optimize PCB layout and firmware reliability for production
🧠 Skills Demonstrated
- PCB Design: High-speed routing, impedance control, power delivery, and signal integrity
- Embedded Programming: STM32 firmware (C), peripheral interfacing (UART, USB, GPIO, ADC)
- Power Systems: Battery charging, voltage regulation, and load-sharing design
- System Integration: Combining modem, MCU, and power management into a cohesive embedded system
⚙️ Technologies & Components
- MCU: STM32 L4 Series
- Modem: Quectel EC25-AF
- Power: USB-C input, Li-ion battery, charger IC
- Communication: USB, UART, CAN
- Tools: KiCad, STM32CubeIDE
Parts
77| Qty | Value | Footprint | References |
|---|---|---|---|
| 9 | 100nf | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C1, C2, C3, C5, C7, C24, C27, C33, C39 |
| 6 | PTVS12VZ1USK | Diode_SMD:Nexperia_DSN1608-2_1.6x0.8mm | D1, D2, D3, D4, D5, D6 |
| 5 | 100nf | Capacitor_SMD:C_0402_1005Metric_Pad0.74x0.62mm_HandSolder | C10, C11, C13, C15, C17 |
| 5 | 1uf | Capacitor_SMD:C_0402_1005Metric_Pad0.74x0.62mm_HandSolder | C9, C12, C14, C16, C18 |
| 5 | 1uf | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C19, C20, C21, C22, C31 |
| 4 | 10k | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | R1, R2, R14, R15 |
| 3 | 10pf | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C26, C30, C35 |
| 3 | 33pf | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C25, C29, C36 |
| 2 | 100uf | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C23, C28 |
| 2 | 10k | Capacitor_SMD:C_0402_1005Metric_Pad0.74x0.62mm_HandSolder | R10, R11 |
| 2 | 4.7k | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | R8, R9 |
| 2 | 470uf | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C4, C6 |
| 2 | 51k | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | R3, R4 |
| 2 | AMS1117-1.5 | Package_TO_SOT_SMD:SOT-223-3_TabPin2 | U5, U6 |
| 2 | Conn_01x02 | Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical | J4, J6 |
| 2 | DTC043ZEBTL | footprints:SOTFL50P160X85-3N | Q2, Q3 |
| 2 | NM | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C37, C38 |
| 1 | 0R | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | R13 |
| 1 | 100k | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | R6 |
| 1 | 10uf | Capacitor_SMD:C_0402_1005Metric_Pad0.74x0.62mm_HandSolder | C8 |
| 1 | 2.2k | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | R12 |
| 1 | 2.2uf | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C32 |
| 1 | 2016504-1 | footprints:CONN1_2016504-1_TEC | J1 |
| 1 | 22uf | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C34 |
| 1 | 330 | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | R5 |
| 1 | 47k | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | R7 |
| 1 | 54-00166 | footprints:barrel jack | J3 |
| 1 | AST-01532MR-R | footprints:SPKR_AST-01532MR-R | LS1 |
| 1 | BSS138 | Package_TO_SOT_SMD:SOT-23 | Q1 |
| 1 | CMA-4544PF-W | footprints:MIC_CMA-4544PF-W | MK1 |
| 1 | Conn_01x08 | Connector_PinHeader_2.54mm:PinHeader_1x08_P2.54mm_Vertical | GND |
| 1 | EC25AFA-512-STD | footprints:modem | U1 |
| 1 | MIC29302WU | footprints:vreg | U3 |
| 1 | NSIM-7-A | footprints:new_sim | J2 |
| 1 | TLV320AIC3104IRHBR | footprints:new_codec | U4 |
| 1 | TXS0108EPWR | footprints:uart_translator | U2 |
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Questions
How big is the Modem breakout PCB?
It measures 48.3 × 85.1 mm and has 4 copper layers, 1.54 mm thick.
What parts does the Modem breakout use?
77 parts, built around the EC25AFA-512-STD, TLV320AIC3104IRHBR, AMS1117-1.5 and MIC29302WU. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Modem breakout KiCad files?
From the asgar-t/phone_project repository on GitHub, at the commit this page was made from: the board is hardware/pcb_designs/modem_breakout/modem_breakout.kicad_pcb and its schematic hardware/pcb_designs/main_board/main_board.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Modem breakout design in my own project?
Its repository states no licence, so its author keeps all rights: ask asgar-t before reusing the design.