README.md
arm-bmw-hw

The ARM Bare Metal Widget (arm-bmw) is an open hardware Cortex-M0 development board with a focus on battery power, non-volatile storage, and debuggability. It is suitable as a battery-powered data logger or a general purpose embedded controller.

The arm-bmw features a small 70 x 43mm footprint, lithium polymer battery and USB power selection, a lithium polymer battery charger, a 2-megabyte Flash memory for data storage, a basic user interface, an FTDI-cable compatible UART header, JTAG-SWD for flashing and debugging, and 16 assorted I/O for connectivity. Its BOM totals to under $15 USD. The arm-bmw is open hardware (CC-BY-4.0 licensed) and open source (MIT licensed).

Order 3 PCBs from <![CDATA[]]>OSH Park<![CDATA[]]> for $23.30 ($7.77 per board): <![CDATA[]]>https://oshpark.com/shared_projects/iBdyoHro<![CDATA[]]>

Photos

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Specifications


<![CDATA[]]>NXP LPC1114FDH28<![CDATA[]]> 32-bit Cortex-M0 microcontroller


Up to 50MHz CPU
12MHz on-chip RC oscillator
32kB Flash, 8kB SRAM
6-ch ADC, I2C, SPI, UART, PWM, Capture

On-board 16-MBit (2-Mbyte) SPI Flash Memory (S25FL216K)
Power


USB (mini-B connector) or LiPo Battery powered
3-position power switch to select power between OFF, BAT, USB
On-board LiPo Battery Charger (<![CDATA[]]>MCP73831T<![CDATA[]]>)
Power LED, Charge LED

User Interface


On-board I2C I/O expander to save microcontroller I/Os (<![CDATA[]]>MCP23008<![CDATA[]]>)
4 LEDs
2 push buttons
2 DIP switches

Input/Output


16-pin 0.1" pitch I/O header with I2C, SPI, Analog, Digital and Power pins
JTAG <![CDATA[]]>Serial Wire Debug<![CDATA[]]> header for Flashing and Debug
UART header, 6-pin <![CDATA[]]>TTL-232R-3V3<![CDATA[]]> compatible

Board


<![CDATA[]]>Dangerous Prototypes SoB DP7043<![CDATA[]]> (70x43mm / 2.756x1.693in) footprint
4 mounting holes

Miscellaneous


Optional external crystal and load capacitor pads
Hand-solderable packages



See the datasheets section below for links to part datasheets.

Hardware Sources

Git: git clone https://github.com/vsergeev/arm-bmw-hw.git

GitHub: <![CDATA[]]>https://github.com/vsergeev/arm-bmw-hw<![CDATA[]]>

Software Sources

Git: git clone https://github.com/vsergeev/arm-bmw-sw.git

GitHub: <![CDATA[]]>https://github.com/vsergeev/arm-bmw-sw<![CDATA[]]>

The arm-bmw-sw project includes a testing suite to verify the correct operation of the UART, SPI, I2C, SPI Flash, I/O Expander, LEDs, and Buttons.

Details and Pinout

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Power and Charging

The arm-bmw provides a female JST-PH connector to accept a 3.7V lithium polymer battery, and a USB mini-B connector to accept 5V power from USB. The USB mini-B connector is only used for power and charging, not data.

A 3-position slide switch on the front selects between off, battery power, and USB power. The red Power LED indicates that 3.3V is present and that the arm-bmw is on. The orange Charge LED indicates that the lithium polymer battery is being charged from 5V USB power.

The onboard <![CDATA[]]>MCP1252<![CDATA[]]> switched capacitor DC/DC converter regulates a 2V to 5.5V input to 3.3V, automatically switching between step down and step up operation as needed to provide 3.3V. This provides continuous power from a 3.7V lithium polymer battery as it drains to below 3.3V volts. The voltage regulator has a maximum output current of 120mA, so the arm-bmw should not be used to drive heavy loads alone.

The <![CDATA[]]>MCP73831T<![CDATA[]]> charge controller facilitates charging the connected lithium polymer battery. It operates whenever 5V power is present via the USB mini-B connector, regardless of the power slide switch state.

Programming

The arm-bmw can be programmed and interactively debugged through its 5-pin JTAG-SWD header, with a SWD dongle like the <![CDATA[]]>ST-LINK/V2<![CDATA[]]>. This dongle and the LPC1114 target are supported by <![CDATA[]]>OpenOCD<![CDATA[]]>. See arm-bmw-sw for configuration scripts for flashing and debugging over JTAG-SWD with openocd. See the JTAG-SWD header pinout below.

The arm-bmw also supports programming over UART with its on-chip ROM bootloader. The 2-pin bootloader header on the front can be jumpered to start the on-chip ROM bootloader on reset. Software like <![CDATA[]]>lpc21isp<![CDATA[]]> or <![CDATA[]]>Flash Magic<![CDATA[]]> can be used to program the LPC1114, over a UART-to-USB or UART-to-RS232 cable connected to the UART header. See the UART header pinout below.

SPI Flash Memory

The arm-bmw features a S25FL216K 16-MBit (2-MByte) SPI Flash for non-volatile storage in data logging applications. This SPI device is connected to the SPI0 controller of the microcontroller, sharing the MOSI, MISO, and SCK pins with the main I/O header. One microcontroller pin (PIO0_2/SSEL0) is dedicated to controlling its chip select.

User Interface

The arm-bmw features a basic user interface, consisting of 4 LEDs, 2 push buttons, and 2 DIP switches. These 4 outputs and 4 inputs (8 I/Os total) are managed by an <![CDATA[]]>MCP23008<![CDATA[]]> I2C I/O expander to conserve I/O pins on the microcontroller. The MCP23008 is connected to the I2C bus of the microcontroller, sharing the SDA and SCL pins with the main I/O header. In addition, one microcontroller pin (PIO0_3) is dedicated to the MCP23008 interrupt. The push buttons and DIP switches are debounced in hardware with an RC filter, to ensure that the MCP23008 interrupt is not spurious and to minimize the need for software debouncing.

The I2C address of the MCP23008 is configured by populating three 0-ohm jumpers on the back of the board, in either a 0 or 1 position, which pull down or up the MCP23008's A0, A1, A2 address pins. By default, these three jumpers are in the 0 position, so the MCP23008 has an address of 0x20 on the I2C bus.

Free software to drive the I2C bus, MCP23008 chip, and manage the UI is avaiable in the arm-bmw-sw library.

System Clock

The LPC1114 microcontroller has an on-chip 12MHz RC oscillator, which can be configured with the internal PLL to provide a 48MHz system clock using no external parts -- this is the default configuration. The arm-bmw also provides pads for an external HC49UP crystal and 0805 load capacitors for cases where a more accurate oscillator or a different multiple is required.

I/O Header Pinout

The I/O header exposes one I2C bus (SDA, SCL), one SPI bus (MISO, MOSI, SCK), and 11 additional pins that may be used as digital I/O, ADC inputs, timer capture inputs, or PWM outputs, depending on the pin's supported functions.




  
BMW Pin
  
uC Pin
  
uC Pin Functions
  
Notes




  
SDA
  
PIO0_5
  
PIO0_5/SDA
  
I/O Expander shares this I2C bus. Pulled up with 10K.


  
SCL
  
PIO0_4
  
PIO0_4/SCL
  
I/O Expander shares this I2C bus. Pulled up with 10K.


  
MISO
  
PIO0_8
  
PIO0_8/MISO0/CT16B0_MAT0
  
SPI Flash shares this SPI bus.


  
MOSI
  
PIO0_9
  
PIO0_9/MOSI0/CT16B0_MAT1
  
SPI Flash shares this SPI bus.


  
SCK
  
PIO0_6
  
PIO0_6/SCK0
  
SPI Flash shares this SPI bus.


  
A0
  
PIO0_11
  
PIO0_11/AD0/CT32B0_MAT3
  



  
A1
  
PIO1_0
  
PIO1_0/AD1/CT32B1_CAP0
  



  
A2
  
PIO1_1
  
PIO1_1/AD2/CT32B1_MAT0
  



  
A3
  
PIO1_2
  
PIO1_2/AD3/CT32B1_MAT1
  



  
A4
  
PIO1_3
  
SWDIO/PIO1_3/AD4/CT32B1_MAT2
  
JTAG-SWD header shares this pin.


  
A5
  
PIO1_4
  
PIO1_4/AD5/CT32B1_MAT3/WAKEUP
  



  
P0
  
PIO0_7
  
PIO0_7/CTS
  



  
P1
  
PIO0_10
  
SWCLK/PIO0_10/SCK0/CT16B0_MAT2
  
JTAG-SWD header shares this pin.


  
P2
  
PIO1_5
  
PIO1_5/RTS/CT32B0_CAP0
  



  
P3
  
PIO1_8
  
PIO1_8/CT16B1_CAP0
  



  
P4
  
PIO1_9
  
PIO1_9/CT16B1_MAT0
  



  
3V3
  
-
  
-
  



  
GND
  
-
  
-
  





JTAG-SWD Header Pinout

Compatible with <![CDATA[]]>ST-LINK/V2<![CDATA[]]> and other JTAG-SWD dongles.




  
BMW Pin
  
uC Pin
  
uC Pin Functions
  
Notes




  
!RST
  
PIO0_0
  
!RESET/PIO0_0
  
Pulled up with 10K.


  
SWDIO
  
PIO1_3
  
SWDIO/PIO1_3/AD4/CT32B1_MAT2
  



  
SWDCLK
  
PIO0_10
  
SWCLK/PIO0_10/SCK0/CT16B0_MAT2
  



  
GND
  
-
  
-
  



  
3V3
  
-
  
-
  





UART Header Pinout

Compatible with the <![CDATA[]]>FTDI TTL-232R-3V3 cable<![CDATA[]]>.




  
BMW Pin
  
uC Pin
  
uC Pin Functions
  
Notes




  
GND
  
-
  
-
  



  
NC
  
-
  
-
  



  
NC
  
-
  
-
  



  
uC RX
  
PIO1_6
  
PIO1_6/RXD/CT32B0_MAT0
  



  
uC TX
  
PIO1_7
  
PIO1_7/TXD/CT32B0_MAT1
  



  
NC
  
-
  
-
  





Schematic, Board, BOM

Schematic

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Board Layout

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Bill of Materials




  
Qty
  
Part
  
Description
  
Part Number
  
Order Qty
  
Total Price




  
1
  
U1
  
ARM Cortex-M0 MCU
  
Arrow LPC1114FDH28/102:5
  
1
  
3.07


  
1
  
U2
  
SPI Flash Memory
  
Digi-key 1274-1052-ND
  
1
  
0.32


  
1
  
U3
  
I2C I/O Expander
  
Digi-key MCP23008-E/SO-ND
  
1
  
1.22


  
1
  
U4
  
3.3V Regulator
  
Digi-key MCP1252-33X50I/MS-ND
  
1
  
1.64


  
1
  
U5
  
LiPo Charger
  
Digi-key MCP73831T-2ACI/OTCT-ND
  
1
  
0.67


  
8
  
C3, C4, C5, C6, C10, C11, C13, C14
  
C 0805 0.1uF
  
Digi-key 1276-1099-1-ND
  
10
  
0.44


  
2
  
C9, C12
  
C 0805 1uF
  
Digi-key 1276-1066-1-ND
  
5
  
0.50


  
2
  
C15, C16
  
C 0805 4.7uF
  
Digi-key 1276-1244-1-ND
  
5
  
0.75


  
2
  
C7, C8
  
C 1206 10uF
  
Digi-key 1276-1075-1-ND
  
5
  
1.15


  
8
  
R1, R7, R8, R9, R14, R15, R16, R17, R18, R19, R27
  
R 0805 10k
  
Digi-key 1276-5332-1-ND
  
15
  
0.30


  
4
  
R10, R11, R12, R13
  
R 0805 100k
  
Digi-key 1276-3512-1-ND
  
10
  
0.20


  
6
  
R20, R21, R22, R23, R24, R25
  
R 0603 0 jumper
  
Digi-key RHM0.0CGCT-ND
  
10
  
0.10


  
4
  
LED1, LED2, LED3, LED4
  
Green LED
  
Digi-key 475-1410-1-ND
  
5
  
0.40


  
1
  
LED_PWR
  
Red LED
  
Digi-key 475-1415-1-ND
  
2
  
0.16


  
1
  
LED_CHG
  
Orange LED
  
Digi-key 754-1130-1-ND
  
2
  
0.40


  
5
  
R2, R3, R4, R5, R6, R26
  
R 0805 for LED 1.5k
  
Digi-key 1276-5533-1-ND
  
10
  
0.18


  
1
  
CON_BAT
  
JST-PH Connector
  
Digi-key 455-1749-1-ND
  
1
  
0.56


  
1
  
CON_USB
  
USB Mini-B Connector
  
Digi-key 151-1206-1-ND
  
1
  
0.41


  
1
  
JP_,TP_
  
40p header break-away
  
Digi-key S1012EC-30-ND
  
1
  
0.48


  
1
  
JP_UART
  
6p header right angle
  
Digi-key S1112EC-06-ND
  
1
  
0.23


  
1
  
SW_PWR
  
Slide switch
  
Digi-key 563-1095-1-ND
  
1
  
0.63


  
2
  
SW_B0, SW_B1
  
Tactile switch
  
Digi-key 450-1792-1-ND
  
2
  
0.40


  
1
  
SW_DIP
  
2-pos DIP switch
  
Digi-key 450-2045-ND
  
1
  
0.81


  
1 OPT
  
BATTERY
  
3.7V LiPo Battery
  
SparkFun <![CDATA[]]>PRT-00731<![CDATA[]]>
  
1
  
4.95


  
4 OPT
  
STANDOFF
  
10mm Nylon Standoff
  
Digi-key 25510K-ND
  
4
  
2.36


  
4 OPT
  
STANDOFF SCREW
  
7mm Nylon Screw
  
Digi-key 29341K-ND
  
4
  
0.76


  
DNP
  
C1, C2
  
C 0805 xtal load caps
  
-
  
-
  
-


  
DNP
  
Q1
  
Crystal
  
-
  
-
  
-


  

  
Parts Total
  

  

  

  
$15.02




The parts total does not include the PCB, LiPo battery, or standoffs.

Order 3 PCBs from <![CDATA[]]>OSH Park<![CDATA[]]> for $23.30 ($7.77 per board): <![CDATA[]]>https://oshpark.com/shared_projects/iBdyoHro<![CDATA[]]>

The unit price of a complete arm-bmw comes out to $22.79, with the BOM parts above and PCBs from OSH Park.

Datasheets


U1, ARM Cortex-M0 MCU, LPC1114FDH28: <![CDATA[]]>site<![CDATA[]]>, <![CDATA[]]>datasheet<![CDATA[]]>, <![CDATA[]]>user manual<![CDATA[]]>
U2, SPI Flash Memory, S25FL216K: <![CDATA[]]>datasheet<![CDATA[]]>
U3, I2C I/O Expander, MCP23008: <![CDATA[]]>site<![CDATA[]]>, <![CDATA[]]>datasheet<![CDATA[]]>
U4, 3.3V DC/DC Converter, MCP1252: <![CDATA[]]>site<![CDATA[]]>, <![CDATA[]]>datasheet<![CDATA[]]>
U5, LiPo Charge Controller, MCP73831T: <![CDATA[]]>site<![CDATA[]]>, <![CDATA[]]>datasheet<![CDATA[]]>


Change Log


Revision 2 - 06/06/2014


Schematic


Add Dangerous Prototypes DP7043 pcb footprint and mounting holes
Add lipo battery charger and charge status led
Add mini-b usb connector for charging or usb power
Add capacitors for hardware debouncing for 2 pos dip switch
Change all 0603 size components to 0805 size
Change C12 size to 0805 (same as C9)
Change 0402 size for I2C IO expander address jumpers to 0603 size
Change I2C pull-ups to 10k
Change BL bootloader switch to a pin header jumper
Change test points to single pin headers

Layout


Change to longer pads on io expander
Change to longer pads on voltage regulator
Change test point pin headers to 0.1" pitch apart
Move passives away from I2C IO expander for easier soldering
Move passives away from voltage regulator for easier soldering
Label the UART header pins

BOM


Change power switch from mom-on-mom to on-on-on
Change spi flash size from 8mbit to 16mbit (same price)
Change to taller 2-pos DIP switch


Revision 1 - 09/16/2013


Initial release



License

arm-bmw-hw is <![CDATA[]]>CC-BY-4.0<![CDATA[]]> licensed.