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Coconut

The Coconut board is an advanced communication controller for up to six RS232 ports. It is equipped with three ATmega128 CPUs, which are interconnected by an I2C bus. All CPUs are independently running NutOS. Allthough the Coconut board may be useful on its own, it has been mainly designed to plug on top of an Ethernut board. In this case the two RS232 ports from the Ethernut are also routed to the Coconut's RS232 port connector, providing a total of eight serial ports.

A second connector offers freely programmable LED indicator outputs as well as shift register signals to add a large number of low speed digital I/O ports. The shift register are only available when Coconut has been connected to an Ethernut board.

Two additional boards are available to easily build up a complete system. The Coconect board can be connected to the Coconut RS232 connector and provides 8 DB-9 connectors. It may be equipped with female (DCE) or male (DTE) connectors.

The second board, IONut, will be connected to Coconut's digital I/O port. It offers 16 opto isolated inputs and 8 relay outputs. All contacts are available at plugable screw terminals.

RS232 I/O Port

All RS232 signals are available on a 34 pin connector. The Coconect board can be directly plugged in with a 1:1 flat ribbon cable.

Each port offers RTS/CTS hardware handshaking. If full modem handshaking is required, then two ports may be combined to a single one, using a different Coconect board.

Pin	Signal	Description
1	TD1	Ethernut PE1 Serial port 2 data output
3	RD1	Ethernut PE0 Serial port 2 data input
5	TD0	Ethernut PD3 Serial port 1 data output
7	RD0	Ethernut PD2, if JP8 set Serial port 1 data input
9	TD3	Coconut CPU1 PE1 Serial port 4 data output
11	RD3	Coconut CPU1 PE0 Serial port 4 data input
13	TD2	Coconut CPU1 PD3 Serial port 3 data output
15	RD2	Coconut CPU1 PD2 Serial port 3 data input
17	GND	Signal ground
19	TD5	Coconut CPU2 PE1 Serial port 6 data output
21	RD5	Coconut CPU2 PE0 Serial port 6 data input
23	TD4	Coconut CPU2 PD3 Serial port 5 data output
25	RD4	Coconut CPU2 PD2 Serial port 5 data input
27	TD7	Coconut CPU3 PE1 Serial port 8 data output
29	RD7	Coconut CPU3 PE0 Serial port 8 data input
31	TD6	Coconut CPU3 PD3 Serial port 7 data output
33	RD6	Coconut CPU3 PD2 Serial port 7 data input

Pin	Signal	Description
2	CTS1	Ethernut PD4 Serial port 2 handshake output
4	RTS1	Ethernut PE7 Serial port 2 handshake input
6	CTS0	Ethernut PE1 Serial port 1 handshake output
8	RTS0	Ethernut PE3 Serial port 1 handshake input
10	CTS3	Coconut CPU1 PD4 Serial port 4 handshake output
12	RTS3	Coconut CPU1 PE7 Serial port 4 handshake input
14	CTS2	Coconut CPU1 PE2 Serial port 3 handshake output
16	RTS2	Coconut CPU1 PE3/PE6 Serial port 3 handshake input
18	GND	Signal ground
20	CTS5	Coconut CPU2 PD4 Serial port 6 handshake output
22	RTS5	Coconut CPU2 PE7 Serial port 6 handshake input
24	CTS4	Coconut CPU2 PE2 Serial port 5 handshake output
26	RTS4	Coconut CPU2 PE3/PE6 Serial port 5 handshake input
28	CTS7	Coconut CPU3 PD4 Serial port 8 handshake output
30	RTS7	Coconut CPU3 PE7 Serial port 8 handshake input
32	CTS6	Coconut CPU3 PE2 Serial port 7 handshake output
34	RTS6	Coconut CPU3 PE3/PE6 Serial port 7 handshake input

Digital I/O Port

A 26 pin connector contains all digital signals for 10 LED outputs and 5 shift register signals.

2 LED outputs are controlled by each Coconut CPU, typically used to indicate serial I/O activity. The remaining 4 LED outputs can be used by an Ethernut board, if one is attached. Two of them may be used as serial I/O indicators and the other two can show Ethernet link and activity. However, all LEDs are under full software control and may serve other purposes.

The number of digital inputs and outputs, that can be attached to the shift register I/O is theoretically unlimited, But the scan and update time increases with its number. Please note, that the shift register I/O is only available when the Coconut is attached to an Ethernut board.

Pin	Signal	Description
1	DC	Unregulated supply
3	DC	Unregulated supply
5	ICOM8	Coconut CPU3 PB6 Serial port 8 LED
7	ICOM6	Coconut CPU2 PB6 Serial port 6 LED
9	ICOM4	Coconut CPU1 PB6 Serial port 4 LED
11	ICOM2	Ethernut PB6 Serial port 2 LED
13	GND	Signal ground
15	GND	Signal ground
17	GND	Signal ground
19	GND	Signal ground
21	GND	Signal ground
23	GND	Signal ground
25	GND	Signal ground

Pin	Signal	Description
2	DC	Unregulated supply
4	DC	Unregulated supply
6	ICOM7	Coconut CPU3 PB4 Serial port 7 LED
8	ICOM5	Coconut CPU2 PB4 Serial port 5 LED
10	ICOM3	Coconut CPU1 PB4 Serial port 3 LED
12	ICOM1	Ethernut PB4 Serial port 1 LED
14	IACT	Ethernut PE6 Activity LED
16	ILINK	Ethernut PE4 Link LED
18	LDOUT	Ethernut PB5 Digital output latch
20	LDIN	Ethernut PB7 Digital input latch
22	SERCLK	Ethernut PD7 Digital data clock
24	SEROUT	Ethernut PD6 Digital data output
26	SERIN	Ethernut PD5 Digital data input

Ethernut Expansion Port

As mentioned before, the main purpose of the Coconut board is to serve as an Ethernut Add-On.

The following table shows, which Ethernut expansion signals are used by the Coconut board. Pins not shown are not connected.

Pin	Signal	Coconut Usage
3	VCC5	+5V, if JP6 closed
5	GND	Signal ground
7	GND	Signal ground
9	RESET	Not connected
39	PE0	Serial port 2 data input
41	PE2	Serial port 1 handshake output
43	PE4	Link LED
45	PE6	Activity LED
47	PB0	Reset CPU1
49	PB2	Reset CPU3
51	PB4	Serial port 1 LED
53	PB6	Serial port 2 LED
55	PD0	TWI bus clock
57	PD2	Serial port 1 data input, if JP8 closed
59	PD4	Serial port 2 handshake output
61	PD6	Digital data output

Pin	Signal	Coconut Usage
4	VCC5	+5V, if JP6 closed
6	GND	Signal ground
8	GND	Signal ground
10	DC	Unregulated supply, if JP7 closed
40	PE1	Serial port 2 data output
42	PE3	Serial port 1 handshake input
44	PE5	Not connected
46	PE7	Serial port 2 handshake input
48	PB1	Reset CPU2
50	PB3	Not connected
52	PB5	Digital output latch
54	PB7	Digital input latch
56	PD1	TWI bus data
58	PD3	Serial port 1 data output
60	PD5	Digital data input
62	PD7	Digital data clock

Power Supply Options

An external power supply can be connected to either the Ethernut board, the Coconut board or both.

JP6	JP7	IC12	Supply Input
Open	Open	Mounted	Both required, Ethernut and Coconut
Close	Open	Not mounted	Ethernut only
Open	Close	Mounted	Ethernut or Coconut
Close	Close	Not mounted	Ethernut or Coconut

Schematics

cnut10b-s1.pdf Page 1: Ethernut Interface

cnut10b-s2.pdf Page 2: Coconut CPU 1

cnut10b-s3.pdf Page 3: Coconut CPU 2

cnut10b-s4.pdf Page 4: Coconut CPU 3

cnut10b-s5.pdf Page 5: Digital Interface And Power Supply