HardLabs

Circuit tap

gcoonrod·circuit-tap

Circuit tap PCB layout, top view — open source AVR/Arduino board by gcoonrod

About the Circuit tap PCB

Circuit tap is an open source AVR/Arduino PCB design by gcoonrod, published on GitHub under the Apache-2.0 license. It is a 4-layer board measuring 99.1 × 75.7 mm, with 58 components from 34 distinct parts.

Its main chip is the ATMEGA4809-PF, from the AVR/Arduino family. Other key parts include the MCP2221A-I/P and CD74HC165E. By type, the board carries 18 capacitors, 11 connectors, 8 ICs, 8 diodes, 7 resistors and 4 switches.

It belongs with the retro computing designs in this gallery.

From the project

A low-speed digital logic analyzer designed around 74HC165 shift registers and the ATMega4809 MCU.

A low-speed digital logic analyzer designed around 74HC165 shift registers and the ATMega4809 MCU.

The Circuit Tap is designed to serve as a digital logic analyzer for primarily low speed circuits (<= 1Mhz). It is intended to aid in debugging the RetroStack, a 6502 based hobbyist computer. As I do not (at the time of designing this tool) own an oscilliscope or logic analyzer, I needed a way to monitor the address bus, data bus, and numerous control signals of the RetroStack while the clock was freely running. For very simple programs it was sufficient to use a manually stepped clock to…

Circuit tap, from the project README
From the project README

Main components on the Circuit tap

MCP2221A-I/PATMEGA4809-PFCD74HC165E

Circuit tap bill of materials (BOM)

58 components, 34 distinct parts.

QtyPartRefs
1
MCP2221A-I/P
Microchip
U1
1
ATMEGA4809-PF
Microchip
U2
6
CD74HC165E
Texas Instruments
U3, U4, U5, U6, U7, U8
1
ACH-20.000MHZ-EK
ABRACON
X1
1
UJ2-BH-1-TH
CUI Devices
J1
1
HDR_UPDI
Amphenol
J2
1
HDR_PORTA
Wurth Elektronik
J3
1
HDR_PORTB
Wurth Elektronik
J4
1
HDR_PORTC
Wurth Elektronik
J5
1
HDR_PORTD
Wurth Elektronik
J6
1
HDR_PORTE
Wurth Elektronik
J7
1
HDR_PORTF
Wurth Elektronik
J8
1
HDR_HSIO
Wurth Elektronik
J9
1
HDR_DUT_CLK
Preci-dip
J10
1
HDR_SD
Wurth Elektronik
J11
1
SW_ARM
CUI Devices
SW1
1
SW_USB_RST
TE Connectivity / P&B
SW2
1
SW_MCU_RST
TE Connectivity / P&B
SW3
1
SW_CLK
CUI Devices
SW4
1
P6KE-AT
YAGEO
D1
Show 14 more
QtyPartRefs
1
LED_PWR
Kingbright
D4
1
LED_ARM
Kingbright
D5
1
LED_RUN
Kingbright
D6
1
LED_ERR
Kingbright
D7
1
LED_END
Kingbright
D8
1
LED_TX
Kingbright
D9
1
LED_RX
Kingbright
D10
1
600R
Laird Performance Materials
L1
1
10n
Vishay
C1
12
100n
Vishay
C2, C4, C5, C6, C7, C8, C9, C10 +4
1
4u7
Panasonic
C3
4
1u
TDK
C16, C17, C18, C19
6
1k
Vishay
R1, R2, R3, R4, R5, R6
1
1k
Bourns
RN1

Circuit tap design files

The KiCad project lives in the gcoonrod/circuit-tap repository on GitHub; these links point at the commit this page was built from.

Circuit tap: common questions

What microcontroller does the Circuit tap use?

The Circuit tap is built around the ATMEGA4809-PF, from the AVR/Arduino family.

How big is the Circuit tap PCB?

The Circuit tap measures 99.1 × 75.7 mm, has 4 copper layers and is 1.6062 mm thick.

How many components are on the Circuit tap?

58 components, from 34 distinct parts. The full bill of materials is listed on this page.

Where can I download the Circuit tap design files?

From the gcoonrod/circuit-tap repository on GitHub, which has the KiCad layout and the schematic; the links under Design files point to each one.

Can I use the Circuit tap design in my own project?

Yes, under the terms of its Apache-2.0 license, which gcoonrod chose for the repository.

Can I test firmware for the Circuit tap without the hardware?

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

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