2 layers90.3 × 42.5 mm Tos io, the printed circuit board in 3D

Tos io

Size: 90.3 × 42.5 mm
Copper layers: 2
Thickness: 1.6 mm
Parts: 27
Nets: 54
Pads: 182
Tracks, vias: 272, 19
Pours: 1
Routed: Yes
KiCad: KiCad 9.0 (file 20241229)
Created: 5 Feb 2025
Updated: 29 Jul 2026

Overview

Tos io is an open-source printed circuit board by apuder, from the apuder/tos repository on GitHub. It is a 2-layer board of 90.3 × 42.5 mm with 27 parts on 54 nets, routed with 272 tracks and 19 vias.

It is built around the MAX232N. Its parts include 8 resistors, 6 connectors, 5 capacitors, 1 IC and 1 diode.

Main components

MAX232N
PDIP-160℃~+70℃ 120Kbps 2 2 4.5V~5.5V Transceiver PDIP-16 RS232 ICs ROHSTexas InstrumentsRS232 ICs

README

README.md

TOS Board Connection Map (v2.2)

Raspberry Pi Connecter

Raspberry Pi Physical Pin	GPIO Pin	TOS Connection	Description
1	3.3v	3.3v line (jumpered with pi pin 1)	3.3v
2	5v	5v line (jumpered with pin 4)	5v
3	GPIO 2 / SDA1	NC	NC
4	5v	5v line (jumpered with pin 2)	5v
5	GPIO 3 / SCL1	NC	NC
6	GND	GND (all grounds jumpered)	Ground
7	GPIO 4	NC	NC
8	GPIO 14 / TXD	MAX3232 Pin 11	TX TTL
9	GND	GND (all grounds jumpered)	Ground
10	GPIO 15 / RXD	MAX3232 Pin 12	RX TTL
11	GPIO 17	Blue LED through R3 (220 Ohm)	LED Blue
12	GPIO 18	Red LED through R1 (330 Ohm)	LED Red
13	GPIO 27	Green LED through R2 (220 Ohm)	LED Green
14	GND	GND (all grounds jumpered)	Ground
15	GPIO 22	SW1 - Pull up to 3.3v through R6 (4.7K Ohm)	Button
16	GPIO 23	Keyboard pin 5	PS2 Keyboard CLK
17	3.3v	3.3v line (jumpered with pi pin 17)	3.3v
18	GPIO 24	Keyboard Pin 1	PS2 Keyboard Data
19	GPIO 10 / MOSI	PMOD pin 2	PMOD 2 MOSI
20	GND	GND (all grounds jumpered)	Ground
21	GPIO 9 / MISO	PMOD pin 3	PMOD 3 MISO
22	GPIO 25	NC	NC
23	GPIO 11 / SCLK	PMOD pin 4	PMOD 4 SCK
24	GPIO 8 / CE0	PMOD pin 1	PMOD 1 CS
25	GND	GND (all grounds jumpered)	Ground
26	GPIO 7 / CE1	NC	NC
27	GPIO 0 / ID_SD (SDA0)	Mouse Pin 1	PS2 Mouse Data
28	GPIO 1 / ID_SC (SCL0)	Mouse Pin 5	PS2 Mouse CLK
29	GPIO 5	NC	NC
30	GND	GND (all grounds jumpered)	Ground
31	GPIO 6	NC	NC
32	GPIO 12 / PWM0	PMOD pin 7	PMOD7 - Int
33	GPIO 13 / PWM1	NC	NC
34	GND	GND (all grounds jumpered)	Ground
35	GPIO 19	NC	NC
36	GPIO 16	PDOD pin 8	PMOD8 - Reset
37	GPIO 26	NC	NC
38	GPIO 20 / PCM_DIN	PMOD pin 9	PMOD9
39	GND	GND (all grounds jumpered)	Ground
40	GPIO 21 / PCM_DOUT	PMOD pin 10	PMOD10

RS-232 Connecter

RS-232 Connector	TOS Connection	Description
1	NC	NC
2	MAX3232 Pin 13	RX
3	MAX3232 Pin 14	TX
4	NC	NC
5	GND	Ground
6	NC	NC
7	Jumpered to RS232 Pin 8	Jumpered to RS232 Pin 8
8	Jumpered to RS232 Pin 7	Jumpered to RS232 Pin 7
9	NC	NC

MAX3232 chip

MAX3232	TOS Connection	Description
1	C1+ (0.1uf) to MAX3232 pin 3
2	C4+ (0.1uf) to GND
3	C1- (0.1uf) to MAX3232 pin 1
4	C2+ (0.1uf) to MAX3232 pin 5
5	C2- (0.1uf) to MAX3232 pin 4
6	C3- (0.1uf) to GND
7	NC	NC
8	NC	NC
9	NC	NC
10	GND	Ground
11	PI Physical pin 8	TXTTL
12	Pi Physical Pin 10	RXTTL
13	RS232 Pin 2	RX
14	RS232 Pin 3	TX
15	GND	Ground
16	3.3v	3.3v

PMOD Connecter

PMOD	GPIO Pin	TOS Connection	Description
1	GPIO 8 / CE0	Pi Physical Pin 24	PMOD 1 - CS
2	GPIO 10 / MOSI	Pi Physical Pin 19	PMOD 2 - MOSI
3	GPIO 9 / MISO	Pi Physical Pin 21	PMOD 3 - MISO
4	GPIO 11 / SCLK	Pi Physical Pin 23	PMOD 4 - SClock
5		GND	Ground
6		3.3v	3.3v
7	GPIO 12 / PWM0	Pi Physical Pin 32	PMOD 7 - INT
8	GPIO 16	Pi Physical Pin 36	PMOD 8 - RESET
9	GPIO 20 / PCM_DIN	Pi Physical Pin 38	PMOD 9
10	GPIO 21 / PCM_DOUT	Pi Physical Pin 40	PMOD 10
11		GND	Ground
12		3.3v	3.3v

PS2 Mouse Connecter

PS2 Mouse	GPIO Pin	TOS Connection	Description
1	GPIO 0 / ID_SD (SDA0)	Pi Physical Pin 27 (pull up to 3.3v through R8 (2K Ohm)	PS2 Mouse Data
2		NC	NC
3		GND	Ground
4		5v	5v
5	GPIO 1 / ID_SC (SCL0)	Pi Physical Pin 28 (pull up to 3.3v through R7 (2K Ohm)	PS2 Mouse Clock
6		NC	NC

PS2 Keyboard Connecter

PS2 Keyboard	GPIO Pin	TOS Connection	Description
1	GPIO 24	Pi Physical Pin 18 (pull up to 3.3v through R5 (2K Ohm)	PS2 Keyboard Data
2		NC	NC
3		GND	Ground
4		5v	5v
5	GPIO 23	Pi Physical Pin 16 (pull up to 3.3v through R4 (2K Ohm)	PS2 Keyboard Clock
6		NC	NC

Breakout Connecter

Breakout	GPIO Pin	TOS Connection	Description
1		GND	Ground
2	GPIO 22	Pi Physical 15 / SW1 - Pull up to 3.3v through R6 (4.7K Ohm)	Button
3	GPIO 18	Pi Physical Pin 12	Red LED
4	GPIO 24	Pi Physical Pin 18 / PS2 Keyboard pin 1	PS2 Keyboar Data
5	GPIO 23	Pi Physical Pin 16 / PS2 Keyboard pin 5	PS2 Keyboard Clock
6		RS-232 pin 2	RX
7		RS-232 pin 3	TX

Parts

Qty	Value	Footprint	References
5	0.1uF	Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder	C1, C2, C3, C4, C5
4	2K	Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder	R4, R5, R7, R8
4	MountingHole_Pad	MountingHole:MountingHole_3mm_Pad_Via	H1, H2, H3, H4
2	220	Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder	R2, R3
1	330	Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder	R1
1	4K7	Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder	R6
1	Conn_01x07	Connector_PinHeader_2.54mm:PinHeader_1x07_P2.54mm_Vertical	J6
1	DE9_Receptacle	Connector_Dsub:DSUB-9_Female_Horizontal_P2.77x2.84mm_EdgePinOffset7.70mm_Housed_MountingHolesOffset9.12mm	J2
1	Keyboard	PocketTRS_Connectors:minidin_6_ps2_pcb_mount	J3
1	LED_RKBG	LED_THT:LED_D5.0mm-4_RGB	D1
1	LOGO	LOGO	G***
1	MAX232	Package_SO:TSSOP-16_4.4x5mm_P0.65mm	U1
1	Mouse	PocketTRS_Connectors:minidin_6_ps2_pcb_mount	J4
1	PMOD SPI 2A	Library:PinSocket_2x06_Top_Bottom_P2.54mm_Vertical	J5
1	RaspPi Pin Header	Connector_PinHeader_2.54mm:PinHeader_2x20_P2.54mm_Vertical	J1
1	STATUS	Button_Switch_THT:SW_PUSH_6mm	SW1

Questions

How big is the Tos io PCB?

It measures 90.3 × 42.5 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Tos io use?

27 parts, built around the MAX232N. 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 Tos io KiCad files?

From the apuder/tos repository on GitHub, at the commit this page was made from: the board is kicad/tos-io.kicad_pcb and its schematic kicad/tos-io.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the Tos io design in my own project?

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

Project files

Show this board on your page

A live frame, for any web page

<iframe src="https://pcbkit.io/embed/boards/apuder-tos" title="Tos io in PCBKit" width="100%" height="480" style="border:0;border-radius:12px" allow="fullscreen" loading="lazy"></iframe>

A picture

<img src="https://pcbkit.io/embed/boards/apuder-tos.jpg" alt="Tos io" width="1200" height="900">

A picture that opens the board, for a README

[![Tos io](https://pcbkit.io/embed/boards/apuder-tos.jpg?size=s)](https://pcbkit.io/boards/apuder-tos)

Source

Repository: apuder/tos
Board file: kicad/tos-io.kicad_pcb
Commit: e080e14
Licence: Not stated

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