This article describes a direct wiring connection between a standard IDE connector and the CN1 connector on the Sega NAOMI and NAOMI 2 motherboards.
Prepare in advance for the release of DreamShell 4.0.4 ;-)



You can take connectors from cartridges or optical communication boards or a non-working motherboard (98-99 years); they are not soldered there and can be easily removed. You can also buy new connectors; they're still available, but only for soldering, like on last revision of NAOMI from 2001, not a dual sided.

IDE to CN1 Signal Mapping

Pins marked as NC are not connected.

IDE Pin	CN1 Pin	Signal
1	NC	NC
2	GND	GND
3	B34	G1_AD7
4	A35	G1_AD8
5	A33	G1_AD6
6	B36	G1_AD9
7	B32	G1_AD5
8	A37	G1_AD10
9	A31	G1_AD4
10	B38	G1_AD11
11	B30	G1_AD3
12	A39	G1_AD12
13	A29	G1_AD2
14	B40	G1_AD13
15	B28	G1_AD1
16	A41	G1_AD14
17	A27	G1_AD0
18	B42	G1_AD15
19	GND	GND
20	NC	NC
21	A7	G1_DREQ
22	GND	GND
23	B10	/HLY_G1_WR
24	GND	GND
25	A9	/HLY_G1_RD
26	GND	GND
27	B6	G1_IORDY
28	NC	NC
29	B8	/HLY_G1_DACK
30	GND	GND
31	A5	TO_FPGA_139
32	NC	NC
33	B16	HLY_G1_RAL9
34	NC	NC
35	A16	HLY_G1_RAL8
36	B17	HLY_G1_RAL10
37	A11	/HLY_G1_CS0
38	B12	/G1_CS1
39	NC	NC
40	GND	GND

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NAOMI and NAOMI 2 CN1 Connector Pinout

The following table show CN1 pinout for reference.

Pin	Signal	Pin	Signal
A1	5V	B1	NC
A2	TO_IC4_PIN9	B2	GND
A3	TO_IC4_PIN12	B3	FPGA_116 + IC32_PIN5
A4	GND	B4	NC
A5	TO_FPGA_139	B5	5V
A6	GND	B6	G1_IORDY
A7	G1_DREQ	B7	5V
A8	GND	B8	/HLY_G1_DACK
A9	/HLY_G1_RD	B9	5V
A10	GND	B10	/HLY_G1_WR
A11	/HLY_G1_CS0	B11	5V
A12	GND	B12	/G1_CS1
A13	/HLY_G1_ROMCS	B13	5V
A14	GND	B14	/G1_FMCS
A15	NC	B15	5V
A16	HLY_G1_RAL8	B16	HLY_G1_RAL9
A17	5V	B17	HLY_G1_RAL10
A18	HLY_G1_MRA11	B18	GND
A19	HLY_G1_MRA12	B19	HLY_G1_MRA13
A20	GND	B20	HLY_G1_MRA14
A21	HLY_G1_MRA15	B21	5V
A22	HLY_G1_MRA16	B22	HLY_G1_MRA17
A23	5V	B23	HLY_G1_MRA18
A24	HLY_G1_RAH19	B24	GND
A25	HLY_G1_RAH20	B25	NC
A26	GND	B26	NC
A27	G1_AD0	B27	3V3
A28	GND	B28	G1_AD1
A29	G1_AD2	B29	3V3
A30	GND	B30	G1_AD3
A31	G1_AD4	B31	3V3
A32	GND	B32	G1_AD5
A33	G1_AD6	B33	3V3
A34	GND	B34	G1_AD7
A35	G1_AD8	B35	3V3
A36	GND	B36	G1_AD9
A37	G1_AD10	B37	3V3
A38	GND	B38	G1_AD11
A39	G1_AD12	B39	3V3
A40	GND	B40	G1_AD13
A41	G1_AD14	B41	3V3
A42	GND	B42	G1_AD15
A43	NC	B43	3V3
A44	NC	B44	NC
A45	3V3	B45	SH4_RXD
A46	SH4_MD7/TXD	B46	GND
A47	SH4_MD0/SCK	B47	SH4_MD2/RXD2
A48	GND	B48	SH4_MD1/TXD2
A49	SH4_SCK2/MRESET	B49	3V3
A50	SH4_CTS2	B50	SH4_MD8/RTS2

Also you can connect WIZnet W5500 Ethernet adapter to SCI interface.

Thanks to ElectronAsh for initial NAOMI CN1 pinout and megavolt85 for comparison with IDE.