HardLabs

ZX21

fordp2002·ZX21·KiCad/ZX21/ZX21.kicad_pcb

ZX21 PCB layout, top view — open source ESP32 board by fordp2002

About the ZX21 PCB

ZX21 is an open source ESP32 PCB design by fordp2002, published on GitHub under the BSD-3-Clause license. It is a 2-layer board measuring 142 × 100 mm, with 125 components from 67 distinct parts.

Its main chip is the ESP32-WROOM, from the ESP32 family. Other key parts include the ULA 2C210E, AT28C256, Z80A, 62256 and 555. By type, the board carries 46 resistors, 21 capacitors, 16 connectors, 13 ICs, 10 diodes and 1 crystal.

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

From the project

40 Years after the Sinclair ZX81 was released this project aims to preserve the first 4 chip computer

This a computer presevation project for the Sinclair ZX81.

Drop in replacement for a ZX81 Built in 16K+ RAM, no need for a RAM Pack Built in Composite Video Output Barrel Jack power input, center Positive OPTION: Single Joystick port (not compatible with quickfire etc.) OPTION: Switchable to 1K RAM OPTION: Back Porch Support for early ULAs OPTION: Built in support for ZX-Wespi OPTION: ZON-X Compatible Yamaha YM2149F Based Sound OPTION: Switchable between Sinclair ROM OR AT28C256 EEPROM * OPTION: 16 Pin Box Header for DK'Tronics Keyboard

Main components on the ZX21

ULA 2C210EAT28C256Z80A6225655574HCT003V3 PSUESP32-WROOMAZ1117-3.3YM2149GAL16V8YMZ284AS6C4008Extra

ZX21 bill of materials (BOM)

125 components, 67 distinct parts.

QtyPartRefs
1
ULA 2C210E
IC1
1
AT28C256
IC2
1
Z80A
IC3
1
62256
IC4
1
555
IC101
1
74HCT00
IC102
1
3V3 PSU
IC301
1
ESP32-WROOM
IC302
1
AZ1117-3.3
IC303
1
YM2149
IC501
1
GAL16V8
IC502
1
YMZ284
IC503
1
AS6C4008Extra
IC801
1
3.5MHz
X1
1
ZX81BUS
EDGE1
1
Jack-DC
J1
4
Conn_01x03
J101, J203, J204, J302
1
Conn_01x04
J301
1
DB9_Male
J401
1
Conn_01x06
J501
Show 47 more
QtyPartRefs
3
Conn_01x08
J502, J503, J504
1
Conn_02x08_Odd_Even
J601
1
Conn_02x23_Row_Letter_First
J701
2
Conn_01x09
J702, J703
2
Audio-Jack-3
EAR1, MIC1
1
Conn_01x05
KB1
1
Conn_01x08
KB2
1
L7805
REG1
1
10K
RP1
1
10K
RP3
1
EG4208A
S1
2
BC548
TR1, TR2
2
PN2222
TR101, TR102
5
2N3904
TR401, TR402, TR403, TR404, TR405
1
CVBS
VIDEO1
10
1N4148
D1, D2, D3, D4, D5, D6, D7, D8 +2
1
47P
C1
1
100N
C2
1
22uF
C3
3
100N
C4, C9, C501
1
1U
C5
1
100P
C6
2
47P
C7, C12
3
10N
C8, C10, C102
1
47N
C11
2
22U
C101, C302
1
820P
C103
1
82P
C104
1
100N
C105
1
47U 25V
C301
1
10N
C303
4
10K
R1, R101, R102, R401
2
680R
R2, R28
1
18K
R4
1
330R
R5
1
2K2
R6
8
470R
R7, R8, R9, R10, R11, R12, R13, R14
1
220K
R15
15
1K
R16, R17, R18, R19, R20, R21, R22, R23 +7
1
1M
R29
1
10R
R30
5
4K7
R33, R302, R501, R502, R503
1
220R
R34
1
68R
R103
1
56R
R104
2
10K
R105, R106
1
100R
R303

ZX21 design files

The KiCad project lives in the fordp2002/ZX21 repository on GitHub; these links point at the commit this page was built from.

ZX21: common questions

What microcontroller does the ZX21 use?

The ZX21 is built around the ESP32-WROOM, from the ESP32 family.

How big is the ZX21 PCB?

The ZX21 measures 142 × 100 mm, has 2 copper layers and is 1.6 mm thick.

How many components are on the ZX21?

125 components, from 67 distinct parts. The full bill of materials is listed on this page.

Where can I download the ZX21 design files?

From the fordp2002/ZX21 repository on GitHub, which has the KiCad layout; the links under Design files point to each one.

Can I use the ZX21 design in my own project?

Yes, under the terms of its BSD-3-Clause license, which fordp2002 chose for the repository.

Can I test firmware for the ZX21 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.

Similar boards