HardLabs

EngModem-Mini

kd4cbm·EngModem-Mini·hardware/kicad/EngModem_Modular_Routed_Rev5.kicad_pcb

EngModem-Mini PCB layout, top view — open source ESP32 board by kd4cbm
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About the EngModem-Mini PCB

EngModem-Mini is an open source ESP32 PCB design by kd4cbm, published on GitHub under the CERN-OHL-S-2.0 license. It is a 2-layer board measuring 95 × 91 mm, with 47 components from 27 distinct parts.

Its main chip is the ESP32-S3-WROOM-1U, from the ESP32 family. Other key parts include the MAX3237EIPWR, MC7805CD2TR4G, 74HCT245 and LM1086IS-3.3/NOPB. By type, the board carries 12 capacitors, 11 connectors, 10 resistors, 8 diodes, 5 ICs and 1 inductor.

It belongs with the displays & leds, retro computing and iot & wireless designs in this gallery.

From the project

Retro dial-up-modem-styled ESP32-S3 board (RS-232, VFD status display, SD, LEDs) running Zimodem-VFD. KiCad hardware + qualified firmware; Rev5 built and bench-qualified.

A retro dial-up-modem-styled ESP32-S3 board: RS-232 (true DCE levels via MAX3237), a 24x2 character VFD status display, a microSD card slot, 8 status LEDs, and USB-C, built around the ESP32-S3-WROOM-1U module. Runs Zimodem - Bo Zimmerman's Hayes AT-command modem emulator/internet gateway - via the Zimodem-VFD fork, which adds the VFD status display this board uses. The firmware qualified on this exact hardware, further specialised for it, is included in firmware/.

EngModem-Mini, from the project README
From the project README

Main components on the EngModem-Mini

MAX3237EIPWRESP32-S3-WROOM-1UMC7805CD2TR4G74HCT245LM1086IS-3.3/NOPB

EngModem-Mini bill of materials (BOM)

47 components, 27 distinct parts — part numbers from the project's BOM.

QtyPartRefs
1
MAX3237EIPWR
U1
1
ESP32-S3-WROOM-1U
U2
1
MC7805CD2TR4G
LM7805S2/TR
U3
1
74HCT245
U4
1
LM1086IS-3.3/NOPB
LD1086D2T33TR
U5
1
VFD
J1
1
DC_PWR_HEADER
J3
1
MAX-ENCFG
J4
1
MAX-SHDN
J5
1
USB
J6
1
EXP
J7
1
MAX-MBAUD
J8
1
ESP-BOOT
J9
1
ESP-ENABLE
J10
1
Micro_SD_Card
J11
1
DB9
J12
8
LED
D1, D2, D3, D4, D5, D6, D7, D8
1
DFE201210U-2R2M=P2 (2.2uH, 1.2A, 228mR)
L1
4
0.22UF
0.22uf
C1, C2, C3, C4
2
0.1UF
0.1uF
C5, C7
Show 7 more
QtyPartRefs
1
0.33UF
0.33uF
C6
1
10UF
10uF
C8
2
10UF
10uF
C9, C11
2
1UF
1uF
C10, C12
5
750R
R1, R2, R3, R4, R5
3
330R
R6, R7, R8
2
10K
R9, R10

EngModem-Mini design files

The KiCad project lives in the kd4cbm/EngModem-Mini repository on GitHub; these links point at the commit this page was built from.

EngModem-Mini: common questions

What microcontroller does the EngModem-Mini use?

The EngModem-Mini is built around the ESP32-S3-WROOM-1U, from the ESP32 family.

How big is the EngModem-Mini PCB?

The EngModem-Mini measures 95 × 91 mm, has 2 copper layers and is 1.6 mm thick.

How many components are on the EngModem-Mini?

47 components, from 27 distinct parts, with part numbers taken from the project's own BOM. The full bill of materials is listed on this page.

Where can I download the EngModem-Mini design files?

From the kd4cbm/EngModem-Mini repository on GitHub, which has the KiCad layout, the schematic and the BOM; the links under Design files point to each one.

Can I use the EngModem-Mini design in my own project?

Yes, under the terms of its CERN-OHL-S-2.0 license, which kd4cbm chose for the repository.

Can I test firmware for the EngModem-Mini without the hardware?

Yes. HardLabs builds a simulation of the board from its netlist and BOM, so you can run and debug ESP32 firmware against it before you order a PCB.

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