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4 layers210 × 125 mmVoicemail Box, the printed circuit board in 3D

Voicemail Box

KROIA/Voicemail-Box1

Mobile Voicemail System Research Platform

Full screenGitHub.kicad_pcb
Size
210 × 125 mm
Copper layers
4
Thickness
1.6 mm
Parts
165
Nets
260
Pads
792
Tracks, vias
1,470, 258
Pours
224
Routed
Yes
KiCad
KiCad 9.0 (file 20241229)
Created
26 Feb 2025
Updated
24 Oct 2025

Overview

Voicemail Box is an open-source printed circuit board by KROIA, from the KROIA/Voicemail-Box repository on GitHub. It is a 4-layer board of 210 × 125 mm with 165 parts on 260 nets, routed with 1,470 tracks and 258 vias.

It is built around the ESP32-WROOM-32, R-78B3.3-2.0 and TLV320AIC3104EVM, with the ARDUINO UNO R3, ST25R3916-BWLT and LXRW0YV600-054 among its other parts. Its parts include 68 capacitors, 41 resistors, 23 connectors, 12 ICs and 5 switches. It belongs with the ESP32 and AVR (ATmega, ATtiny) boards of this library.

Main components

9

README

README.md

Voicemail-Box

About

Modern-day communication is more and more reliant on smartphones. This can cause issues in numerous situations. It can alienate people with writing, seeing, or technological deficiencies.

Since the development of new electronic systems is often too complicated for non-affine people, the goal is to develop a platform that makes it easier to get started with such a project. The highest priority was given to audio input and output, user differentiation/management, file saving, and transferring those wirelessly.

Repository overview

The repository is structured the following way:

Features

The Voicemailbox Development Platform offers the basic hardware and software components to develop specific use cases out of it. The custom PCB is designed to be flexible for different kind of configurations and the software is built in a modular and structural way, using modern C++ to be able to abstract hardware components better and make it easy to develop custom business logic on to it.

The current state of development features the following:

  • Recording audio from different sources:
    • Audio jack for left and right audio channel.
    • Built-in microphone
  • Playback audio to the audio output jack
  • Filesystem using a SD-Card and easy to use file class for reading and writing files
  • Two different audio encodings for files are supported:
    • WAV Which is a lossless easy to write/read file format for audio data with the downside of beeing very large in filesize.
    • MP3 Which is a more common used audio format, much more compressed and the prefered choice for a application such as this one. The only downside is, that it is not fully supported on a M7 core.
  • Testserver implementation that manages file upload/download. With the help of the ESP32, files can be uploaded/downloaded from a server using a WIFI connection. No user authentication is implemented at the current state of the development.
  • Two free programmable LED's.
  • Four free programmable buttons.
  • Two free programmable analog inputs.

Untested features:

  • Playback using the speaker connection (J603) is implemented in hardware but not implemented and tested in the software.
  • NFC module

Parts

165
QtyValueFootprintReferences
15100nCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC601, C603, C605, C608, C612, C613, C621, C805, C807, C809, C811, C812, C813, C814, C815
134k7Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR101, R102, R103, R805, R806, R807, R808, R809, R810, R811, R812, R813, R814
810nCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC503, C504, C506, C508, C510, C512, C516, C518
72u2Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC505, C507, C509, C513, C515, C517, C519
5LXRW0YV600-054additional parts:LXRW0_MUR-MU502, U503, U504, U505, U506
4100RResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR604, R605, R606, R607
410kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR301, R501, R506, R507
410pCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC501, C502, C531, C533
410uCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC602, C604, C607, C609
447nCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC616, C617, C618, C619
4Push_ButtonButton_Switch_THT:SW_PUSH_6mmSW801, SW802, SW803, SW804
310uCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC302, C806, C808
31uCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC511, C606, C622
347pCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC524, C525, C526
3Conn_02x03_Odd_EvenConnector_PinHeader_2.54mm:PinHeader_2x03_P2.54mm_VerticalJ102, J802, J803
3npCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC614, C615, C620
20RResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR610, R611
2100nCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC301, C401
2100pCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC520, C521
2100uCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC610, C611
2180pCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC532, C534
21k2Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR801, R802
2220RResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR106, R107
2270nInductor_SMD:L_0603_1608Metric_Pad1.05x0.95mm_HandSolderL501, L502
22k2Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR601, R602
22k4Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR503, R504
256pCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC527, C528
25k1Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR701, R702
2680pCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC522, C523
2AudioJack3_SwitchTRadditional parts:Jack_3.5mm_CUI_SJ2-3593D-SMT_HorizontalJ602, J605
2Conn_01x08Connector_PinHeader_2.54mm:PinHeader_1x08_P2.54mm_VerticalJ105, J801
2Conn_02x10_Odd_EvenConnector_PinHeader_2.54mm:PinHeader_2x10_P2.54mm_VerticalJ104, J106
2NetTie_2NetTie:NetTie-2_SMD_Pad0.5mmNT501, NT502
2npResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR608, R609
2potentiometer_RK163Potentiometer_THT:Potentiometer_Alps_RK163_Single_HorizontalRV801, RV802
1100RResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR505
1100kResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR603
110kResistor_SMD:R_Array_Convex_4x0603RN401
11kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR303
11nCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC810
120kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR302
1220RResistor_SMD:R_Array_Convex_4x0603RN402
122nCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC514
127.12MhzCrystal:Crystal_SMD_SeikoEpson_FA128-4Pin_2.0x1.6mmY501
12k7Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR612
147kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR502
174LS07Package_SO:SOIC-14_3.9x8.7mm_P1.27mmU801
1Arduino_UNO_R3additional parts:Arduino_UNO_R3_no_legendA101
1BAV70WPackage_TO_SOT_SMD:SOT-23-3D502
1CMA-4544PF-Wadditional parts:Mic, dia 10mm pitch 2.54mmMK601
1CTS 218-4LPSTJadditional parts:SSOP-8_3.9x5.05mm_P1.27mmSW601
1Conn_01x02Connector_PinHeader_1.27mm:PinHeader_1x02_P1.27mm_VerticalJ501
1Conn_01x03Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_VerticalJ604
1Conn_01x06Connector_PinHeader_2.54mm:PinHeader_1x06_P2.54mm_VerticalJ303
1Conn_02x02_Odd_EvenConnector_PinHeader_2.54mm:PinHeader_2x02_P2.54mm_VerticalJ601
1Conn_02x06_Odd_Evenadditional parts:PinSocket_2x06_P2.54mm_HorizontalJ301
1Conn_02x08_Odd_EvenConnector_PinHeader_2.54mm:PinHeader_2x08_P2.54mm_VerticalJ103
1Conn_02x08_Odd_EvenConnector_PinSocket_2.54mm:PinSocket_2x08_P2.54mm_VerticalCN201
1ESP32-WROOM-32RF_Module:ESP32-WROOM-32U301
1FerriteBead_0603_1.5AInductor_SMD:L_0603_1608Metric_Pad1.05x0.95mm_HandSolderL701
1Green_350mcd_0603PCM_4ms_LED:LED_0603_1608MetricLED804
1MAX98306xDTadditional parts:TDFN-14-1EP_3x3mm_P0.4mm_EP1.78x2.35mmU602
1Micro_SD_Card_Det1Connector_Card:microSD_HC_Hirose_DM3AT-SF-PEJM5J401
1NX3008NBKPackage_TO_SOT_SMD:SOT-23-3Q501
1Phoenix 1844236Connector_Phoenix_MC:PhoenixContact_MC_1,5_4-G-3.5_1x04_P3.50mm_HorizontalJ603
1R-78B3.3-2.0Converter_DCDC:Converter_DCDC_RECOM_R-78B-2.0_THTU701
1Red_100mcd_0603PCM_4ms_LED:LED_0603_1608MetricLED801
1ST25R3916Badditional parts:UFQFPN-32-1EP_5x5mm_P0.5mm_EP3.5x3.5mmU501
1TC2015-1.8VxCTTRPackage_TO_SOT_SMD:SOT-23-5U702
1TLV320AIC3104Package_DFN_QFN:VQFN-32-1EP_5x5mm_P0.5mm_EP3.1x3.1mmU601
1USB_C_Receptacle_PowerOnly_6Padditional parts:USB_C_Receptacle_HRO_TYPE-C-31-M-17J701
1~Connector_PinHeader_2.54mm:PinHeader_2x08_P2.54mm_VerticalCN202
1~Connector_PinHeader_2.54mm:PinHeader_2x17_P2.54mm_VerticalCN205
1~Connector_PinHeader_2.54mm:PinHeader_2x15_P2.54mm_VerticalCN203
1~Connector_PinHeader_2.54mm:PinHeader_2x10_P2.54mm_VerticalCN204

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Questions

How big is the Voicemail Box PCB?

It measures 210 × 125 mm and has 4 copper layers, 1.6 mm thick.

What parts does the Voicemail Box use?

165 parts, built around the ESP32-WROOM-32, R-78B3.3-2.0, TLV320AIC3104EVM and ARDUINO UNO R3. 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 Voicemail Box KiCad files?

From the KROIA/Voicemail-Box repository on GitHub, at the commit this page was made from: the board is Hardware/PCB/voicemail-box.kicad_pcb and its schematic Hardware/PCB/NFC_breakaway.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the Voicemail Box design in my own project?

Its repository states no licence, so its author keeps all rights: ask KROIA before reusing the design.