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SB-mini-II

simonboak·SB-mini-II·Rev 1 Schematic/SB mini II/SB mini II.kicad_pcb

SB-mini-II PCB layout, top view — open source RP2040/RP2350 board by simonboak

About the SB-mini-II PCB

SB-mini-II is an open source RP2040/RP2350 PCB design by simonboak, published on GitHub under the MIT license. It is a 4-layer board measuring 184.2 × 169.5 mm, with 91 components from 44 distinct parts.

Its main chip is the RaspberryPi_Pico, from the RP2040/RP2350 family. Other key parts include the 74HC74, 65C02, 74HC08, 74HC138 and 74HC259. By type, the board carries 28 capacitors, 19 ICs, 18 resistors, 6 connectors, 3 transistors and 3 diodes.

From the project

A homebrewed Apple II clone

- The CPU is a standard 65C02 running at near 1.024 MHz (the original Apple II ran at 1.023 for the 60 Hz models), after dividing the 4.096 MHz crystal by 4. - The 12kB ROM image is placed on the 32k EEPROM. Because there's spare room on this chip a jumper allows for selecting the high or low half of the ROM chip, so I've placed Ardian Black's Deadtest program in there. - 48kB of RAM is accomplished by using one and half 32kB SRAM chips. Figured this was easier to use matching chipd than it was to use a 32kb + 16kB chip. - Address decoding works exactly like the real Apple II. This was mostly…

SB-mini-II, from the project README
From the project README

Main components on the SB-mini-II

74HC7465C0274HC0874HC13874HC259NE55674HC3074HCT13874HC0074HC25128C256CY6225674HC244RaspberryPi_Pico

SB-mini-II bill of materials (BOM)

91 components, 44 distinct parts — part numbers from the project's BOM.

QtyPartRefs
2
74HC74
U1, U13
1
65C02
U2
1
74HC08
U3
3
74HC138
74HCT138
U4, U5, U6
1
74HC259
U7
2
NE556
U8, U9
1
74HC30
U10
1
74HCT138
U11
2
74HC00
U12, U17
1
74HC251
U14
1
28C256
U15
2
CY62256
U16, U18
1
74HC244
U19
1
RaspberryPi_Pico
A1
1
MPSA13
Q1
1
PN2222A
Q2
1
IRF5305
Q3
1
4MHz
Y1
1
GAME I/O
J1
1
DEBUG
J2
Show 24 more
QtyPartRefs
1
12V Input
J3
1
Power Switch
J4
1
Pololu 5V 1A Step-Down Voltage Regulator (D24V10F5)
J5
1
Apple II Power Connector
J6
1
HI ROM
JP1
1
SHIFT KEY MOD
JP2
1
Speaker
LS1
1
RESET
SW1
8
Expansion Slot
Slot0, Slot1, Slot2, Slot3, Slot4, Slot5, Slot6, Slot7
1
1N914
D1
1
1N5240B
D2
1
PWR LED
D3
23
0.1µF
C1, C6, C7, C9, C10, C11, C12, C13 +15
4
22NF
22nF
C2, C3, C4, C5
1
470µF
C8
6
3K3
3k3
R1, R2, R3, R4, R5, R12
2
1k
R6, R17
1
2K5
2k5
R7
4
100
R8, R9, R10, R11
1
10K
R13
1
47K
47k
R14
1
27
R15
1
100K
100k
R18
1
330
R19

SB-mini-II design files

The KiCad project lives in the simonboak/SB-mini-II repository on GitHub; these links point at the commit this page was built from.

SB-mini-II: common questions

What microcontroller does the SB-mini-II use?

The SB-mini-II is built around the RaspberryPi_Pico, from the RP2040/RP2350 family.

How big is the SB-mini-II PCB?

The SB-mini-II measures 184.2 × 169.5 mm, has 4 copper layers and is 1.6 mm thick.

How many components are on the SB-mini-II?

91 components, from 44 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 SB-mini-II design files?

From the simonboak/SB-mini-II 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 SB-mini-II design in my own project?

Yes, under the terms of its MIT license, which simonboak chose for the repository.

Can I test firmware for the SB-mini-II without the hardware?

Yes. HardLabs builds a simulation of the board from its netlist and BOM, so you can run and debug RP2040/RP2350 firmware against it before you order a PCB.

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