This is revision A of the Panda1 board. It is part of the Robus project.

Panda1 (Revision A)

Introduction

Panda1 is an expansion board for the PandaBoard OMAP4 ARM processor from Texas Instruments. This expansion board basically provides an LPC1754 ARM microcontroller from NXP Semiconductors that is connected to connected up to a 10-pin header electrically wired to commincate on the Robus intermodule commuications bus. In addition this board provides a place to plug in a D15V35F5S3 from Pololu.

Pictures

The picture below (click on image to get larger):

shows the Panda1 board (a little blurry.)

The picture below (click on image to get larger):

shows Panda1 plugged into a PandaBoard. The Pololu is plugged in rotated 180 degrees to deal with the a Rev. A design error. The narrow board is used for doing In Circuit Serial Programming. The board on the right is used to connect batteries to everything.

The picture below (click on image to get larger):

shows the PandaBoard and the Panda1 support board plugged together. Notice how the 5V power is connected from the Pololu board to the PandaBoard.

Requirements

The following features are required:

The LPC1754 UART1 must connect to Robus.
The PandaBoard SPI must hook to LPC1754 SPI, where the PandaBoard is an SPI master and the LPC1754 is an SPI slave.
There must be a way to program LPC1754 via UART0. This includes being able to trigger LPC1754 reset pin and setting the LPC1754 "boot" pin to toggle between program and run modes.

The following features are desirable:

It is desirable there there be an asynchronous serial data connection from the PandaBoard to LPC1754 UART0 for both programming and debuggin. This includes being able to set reset pin and setting the "boot" pin between program and run modes. (Made it.)
It is desirable to that the PandaBoard be able to communicate with the LPC1754 via an I2C connection. (Made it.)
It is desirable that there be a way to connect one of the LPC1754 CAN peripherals to the 10-pin Robus connector. (Made it.)
It is desirable that there be a standard ARM 14-pin JTAG connector. (Made it.)
It is desirable that there be at least one LED that can be controlled from the LPC1754.
It is desirable that there be a place to connect separate batteries for the motor and logic sides of the 10-pin Robus connector. (Not enough room.)
It is desirable that there be a connection from the battery connectors to a Pololu power regulator board to power the PandaBoard. There should be a connector that connects to the PandaBoard 5VDC power jack. (Mounted on Pololu board instead.)
It is desirable that there be additional UART debugging connectors for LPC1754 UART2 and UART3. (They will be on the GPIO connector instead.)
It is desirable that there be power on LED's for both Logic and Motor connectors. (Did not happen.)
It is desirable that there be additional LPC1754 GPIO pins brought out board edges. (May happen.)

Design

The entire Panda1 project is available as a KiCAD archived ZIP file:

ZIP file

T The following is images are available in the in PS and SVG formats:

Scheamtatic (PS format) (SVG format) (PDF format, possibly stale)
PCB Back Layer (PS format) (SVG format)
PBB Front Layer (PS format) (SVG format)
PBB Front Silk Screen Layer (PS format) (SVG format)
Archive (Zip format) (Gzipped tar Format)

This is my list of pertinent vendor data sheets from my private cache of datasheets:

PandaBoard (PDF)
Overall documentation for the PandaBoard
PandaBoard Schematics (PDF)
The PandaBoard circuit schematics.
MCP2551 (PDF)
A CAN bus transceiver

An inexpensive low drop out voltage regulator.
TXS0104E (PDF)
A 4-channel bi-directional voltage level shifter.
LPC175x (PDF)
An embedded ARM chip from NXP.
Murata Posistor Catalog (PDF)
Resetable fuse catalog.

The outstanding issues are:

On the expansion connector schematic page (page 13) the signal directions seem to be contrary to signal names. In particular, UART4_RXD seems to be an output and UART4_TXD seems to be an input. What gives?
Should I switch to a different voltage regulator with a surface mount heat sink tab? If so, which one?
What value should the termination resistor be? What wattage?

The table below shows the basic connectivity between the 2×14 pin PandaBoard Expansion A (J3) connector and the LPC175x microcontroller. The pins have been grouped into used signal pins, power pins, and unused signal pins:

J3
Pin OMAP
Pin PandaBoard Usage LPC175x
Pin LPC175x
Usage
Used Signal Pins
4 AH23 SPI1 CS3/UART1 RTS ? ?
6 AH19 UART4 TXD 80 RXD0
8 AG20 UART4 RXD 79 TXD0
10 AF23 SPI1 CS1/UART1 RXD ? ?
12 AG22 SPI1 MOSI 45 MOSI1/MOSI
14 AG23 SPI1 CS2/UART1 CTS ? ?
16 AE22 SPI1 CS0 ? ?
18 AE22 SPI1 MISO 46 MISO0/MISO
20 AF22 SPI1 CLK 47 SCK0/SCK
23 AH22 I2C4 SDA 37 SDA1
24 AG21 I2C4 SCL 38 SCL1
Power Pins (all used)
1 - 1.8V (On Board Reg.)
2 - 5VDC (Power Jack)
27 - GND (Digital)
28 - GND (Digital)
Unused Signal Pins
3 B16 GPMC AD7
5 A16 GPMC AD6
7 D15 GPMC AD5
9 C15 GPMC AD4
11 D13 GPMC AD3
13 C13 GPMC AD2
15 D12 GPMC AD1
17 C12 GPMC AD0
19 B12 GPMC WREN
21 B11 GPMC OE
22 D19 GPMC AD15
25 - TWL6030 REGEN1
26 E7 RESET

J3 Pin	OMAP Pin	PandaBoard Usage	LPC175x Pin	LPC175x Usage
Used Signal Pins
4	AH23	SPI1 CS3/UART1 RTS	?	?
6	AH19	UART4 TXD	80	RXD0
8	AG20	UART4 RXD	79	TXD0
10	AF23	SPI1 CS1/UART1 RXD	?	?
12	AG22	SPI1 MOSI	45	MOSI1/MOSI
14	AG23	SPI1 CS2/UART1 CTS	?	?
16	AE22	SPI1 CS0	?	?
18	AE22	SPI1 MISO	46	MISO0/MISO
20	AF22	SPI1 CLK	47	SCK0/SCK
23	AH22	I2C4 SDA	37	SDA1
24	AG21	I2C4 SCL	38	SCL1
Power Pins (all used)
1	-	1.8V (On Board Reg.)
2	-	5VDC (Power Jack)
27	-	GND (Digital)
28	-	GND (Digital)
Unused Signal Pins
3	B16	GPMC AD7
5	A16	GPMC AD6
7	D15	GPMC AD5
9	C15	GPMC AD4
11	D13	GPMC AD3
13	C13	GPMC AD2
15	D12	GPMC AD1
17	C12	GPMC AD0
19	B12	GPMC WREN
21	B11	GPMC OE
22	D19	GPMC AD15
25	-	TWL6030 REGEN1
26	E7	RESET

The table below shows the basic connectivity of the LPC175x microcontroller pins. The pins are ordered by function and the RESET pin is replicated in two places:

Pin Port
Name Usage
Name To
UART0 (goes to Pandaboard and ICSP conn.)
80 P0.3 RXD0 PB UART4 TXD/ICSP TXD
79 P0.2 TXD0 PB UART4 RXD/ICSP RXD
14 - RESET PB SPI1 CS?/ICSP NRESET (shared with PB and JTAG)
41 - NMI (PROG) PB SPI1 CS?/ICSP PGM
UART1/CAN2 (both go to the CAN tranceiver)
60 P2.0 TXD1 CAN TXD
51 P2.7 RD2
59 P2.1 RXD1 CAN RXD
50 P2.8 TD2
SPI1 (goes to PandaBoard)
45 P0.18 MOSI1/MOSI PB SPI1 MOSI
46 P0.17 MISO1/MISO PB SPI1 MISO
47 P0.15 SCK1/SCK PB SPI1 SCK
48 P0.16 SSEL1/SSEL PB SPI1 CS?
JTAG (goes to 14-pin JTAG connector)
1 - TDO JTAG TDO
2 - TDI JTAG TDI
3 - TMS JTAG TMS
4 - TRST JTAG TRST
5 - TCK JTAG TCK
14 - NRESET JTAG Reset (shared with ICSP and PB)
I2C (goes to PandaBoard)
37 P0.0 SDA1 PB SDA
38 P0.1 SCL1 PB SCL
UART2 (UART2 connector)
39 P0.10 TXD2 UART2 TXD
40 P0.11 RXD2 UART2 RXD
UART3 (UART3 connector)
65 P4.28 TXD3 UART3 TXD
68 P4.29 RXD3 UART3 RXD

Pin	Port Name	Usage Name	To
UART0 (goes to Pandaboard and ICSP conn.)
80	P0.3	RXD0	PB UART4 TXD/ICSP TXD
79	P0.2	TXD0	PB UART4 RXD/ICSP RXD
14	-	RESET	PB SPI1 CS?/ICSP NRESET (shared with PB and JTAG)
41	-	NMI (PROG)	PB SPI1 CS?/ICSP PGM
UART1/CAN2 (both go to the CAN tranceiver)
60	P2.0	TXD1	CAN TXD
51	P2.7	RD2
59	P2.1	RXD1	CAN RXD
50	P2.8	TD2
SPI1 (goes to PandaBoard)
45	P0.18	MOSI1/MOSI	PB SPI1 MOSI
46	P0.17	MISO1/MISO	PB SPI1 MISO
47	P0.15	SCK1/SCK	PB SPI1 SCK
48	P0.16	SSEL1/SSEL	PB SPI1 CS?
JTAG (goes to 14-pin JTAG connector)
1	-	TDO	JTAG TDO
2	-	TDI	JTAG TDI
3	-	TMS	JTAG TMS
4	-	TRST	JTAG TRST
5	-	TCK	JTAG TCK
14	-	NRESET	JTAG Reset (shared with ICSP and PB)
I2C (goes to PandaBoard)
37	P0.0	SDA1	PB SDA
38	P0.1	SCL1	PB SCL
UART2 (UART2 connector)
39	P0.10	TXD2	UART2 TXD
40	P0.11	RXD2	UART2 RXD
UART3 (UART3 connector)
65	P4.28	TXD3	UART3 TXD
68	P4.29	RXD3	UART3 RXD

Miscellaneous notes:

OSTTA024163 is a reasonable 2 position terminal block. Jameco & Digkey stock.
SN74HC11D is 1.27mm pitch with lands centered on 4.8mm. Package is 3.80-4.00mm wide. Use SO14E.
TXS0104ED is 1.27mm pitch with lands centered on 4.8mm. Package is 3.80-4.00mm wide. Use SO14E.

Issues

The following issues were encountered:

The Pololu voltage regulator has the pins backwards.
The SOT23 footprint for the MCP1700 is wrong.
It might make sense to add an LED.