USB Keyboard Using MSP430 Microcontrollers

Application Report SLAA514 – December 2011

USB Keyboard Using MSP430™ Microcontrollers David Racine, Luis Reynoso ............................................................................................ MSP430 Apps ABSTRACT This application report describes a low-cost highly-flexible composite USB keyboard implementation based on MSP430F5xx/MSP430F6xx families. Schematics and software are included allowing for an easy implementation and customization. The document explains basic necessary concepts but familiarity with the MSP430™ USB Developers Package (MSP430USBDEVPACK) and USB HID specification is assumed. Source code and additional information described in this application report can be downloaded from http://software-dl.ti.com/msp430/msp430_public_sw/mcu/msp430/USBKBD_430/latest/index_FDS.html.

1 2 3 4 5 6 7

Contents Introduction .................................................................................................................. 2 Implementation .............................................................................................................. 2 Software ...................................................................................................................... 6 Hardware and Peripheral Usage ........................................................................................ 12 Using the USB Keyboard ................................................................................................. 12 Schematics ................................................................................................................. 15 References ................................................................................................................. 16 List of Figures

1

Key Matrix .................................................................................................................... 3

2

Keyboard Schematic........................................................................................................ 3

3

Detection of a Key Using Column-Interrupt Method .................................................................... 4

4

Detection of a Key Using Polling Method ................................................................................ 4

5

"Ghost" Key Detection ...................................................................................................... 5

6

USB Keyboard Software Modules ........................................................................................ 6

7

USB Keyboard Flow Diagram ............................................................................................. 7

8

Digital Keyscan Flow Diagram ............................................................................................ 9

9

USB Keyboard in Windows Device Manager .......................................................................... 13

10

Testing the HID Custom Interface ....................................................................................... 14

11

Schematics ................................................................................................................. 15 List of Tables

1

VID/PID Used by the Device .............................................................................................. 5

2

HID Keyboard Report Format ............................................................................................. 8

3

Communication Protocol Report Descriptor ............................................................................. 8

4

Implemented Protocol ...................................................................................................... 8

5

Configuration Constant Table ............................................................................................ 11

6

ScanCodes ................................................................................................................. 11

7

MSP430F550x/5510 Peripheral Usage ................................................................................. 12

8

MSP430F550x/5510 Pinout Usage ..................................................................................... 12

MSP430, Code Composer Studio are trademarks of Texas Instruments. IAR Embedded Workbench is a trademark of IAR Systems. SLAA514 – December 2011 Submit Documentation Feedback

USB Keyboard Using MSP430™ Microcontrollers Copyright © 2011, Texas Instruments Incorporated

1

Introduction

1

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Introduction This application report describes the implementation of a USB keyboard with the following characteristics: • 101 keys, 2 LEDs: standard HID keyboard and LED usage • 16x8 matrix: allows for easy customization of different keyboard layouts • Composite USB device: In addition to the keyboard interface, it includes an HID-datapipe back-channel which can be used to transmit any custom data • HID boot protocol support, allowing keyboard to be used to interface with a PC's BIOS • "Ghost" key handling in software, to prevent errors from multiple key presses • Uses MSP430F550x/5510 low-cost USB family The Texas Instruments MSP430F550x/5510 devices are ultra-low power microcontrollers featuring a powerful 16-bit RISC CPU, 16-bit registers, and constant generators that contribute to maximum code efficiency. In addition, this MSP430 family includes an integrated USB and PHY supporting USB 2.0 fullspeed communication, four 16-bit timers, a high-performance 10-bit analog-to-digital converter (ADC), two universal serial communication interfaces (USCI), hardware multiplier, DMA, real-time clock module with alarm capabilities, and 31 or 47 I/O pins.

2

Implementation

2.1

Key Matrix The USB keyboard presented in this application report implements a key matrix of rows and columns similar to smaller keypads like the one shown in the application report Implementing An Ultralow-Power Keypad Interface with MSP430 (SLAA139). This implementation uses a 16 rows x 8 columns matrix, which allows up to 128 keys, but it actually uses only 101 keys in total. The key matrix is shown in Figure 1.

2


SLAA514 – December 2011 Submit Documentation Feedback

Implementation

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Row0 P2.0

Col0 P1.0

Col1 P1.1

Col2 P1.2

Col3 P1.3

Col4 P1.4

Col5 P1.5

Col6 P1.6

Col7 P1.7

Keypad Enter

Keypad -

Keypad +

Keypad 2

Keypad 3

Keypad .

Keypad 1

Keypad /

Keypad 9

Win

Keypad 7

Home

PageUp

Keypad NumLock

Tab

~ `

1

Q

A

Row1 P2.1 Row2 P2.2

Keypad 0

Row3 P2.3

Right Alt

Left Alt

Row4 P2.4

C

Space bar

F3

F4

CapsLock

3

E

D

Row5 P2.5

X

Z

F2

F1

Esc

2

W

S

Row6 P2.6

V

B

G

T

5

4

R

F

Row7 P2.7

M

N

H

Y

6

7

U

J

Row8 P3.0

> .

ê

| \

F11

F10

9

O

L

Row9 P3.1

Right Shift

Left Shift

Row10 P3.2

< ,

Keypad *

F7

F6

F5

8

I

K

Keypad 8

F9

Row11 P3.3

ç

Row12 P3.4

Right Ctrl

Left Ctrl

Row13 P5.0

? /

é

_ -

F12

0

P

{ [

: ;

Row14 P5.1

“ ‘

Enter

PrtScr

End

+ =

Back space

} ]

Page Down

è

F8

Pause

Scroll Lock

Keypad 4

Keypad 5

Keypad 6

Row15 P2.0

Figure 1. Key Matrix

...

Coln

Col1

Col0

Each key works like a switch, and pulldowns are implemented on each column, keeping the idle state low (see Figure 2).

Row0 Row1 ... Rown-1 Rown

Figure 2. Keyboard Schematic There are multiple ways to scan a key matrix, but this application report uses two methods, referred in this application report as: column-interrupt and polling.



3

Implementation

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In the column-interrupt approach, all rows are actively driven at the same time and columns are configured to interrupt the processor when any single key is pressed. This method is useful in low-power modes, because any key can wake up the microcontroller; however, it is important to remark that the key press is only used for that purpose, because it does not provide the exact key being pressed. Figure 3 shows the key matrix behavior when the Enter key is pressed in column-interrupt mode. Actively driven rows and columns are shown in red. Notice that the Col1 pin would detect a change when the Enter key is pressed, but the effect would be the same for any other pin pressed in the same column.

Row0 P2.0

Col0 P1.0

Col1 P1.1

Col2 P1.2

Keypad Enter

Keypad -

Keypad +

Row1 P2.1 . . . Row14 P5.1

...

Keypad 9

“ ‘

Row15 P2.0

Enter

PrtScr

è

F8

Figure 3. Detection of a Key Using Column-Interrupt Method After the system is awake due to a key press using the column-interrupt approach, the polling method can be used to determine which key(s) is(are) being pressed (see Figure 4). In the polling method, each row is scanned separately driving one row at a time in sequential order. The columns are then read giving the exact keys being pressed.

Row0 P2.0

Col0 P1.0

Col1 P1.1

Col2 P1.2

Keypad Enter

Keypad -

Keypad +

Row1 P2.1 . . . Row14 P5.1 Row15 P2.0

...

Keypad 9

“ ‘

Enter

PrtScr

è

F8

Figure 4. Detection of a Key Using Polling Method One of the caveats when using this method is that particular patterns can cause unwanted connections, known as "ghost" keys. This behavior is caused when three or more keys sharing rows and columns are pressed at the same time (see Figure 5).

4



Implementation

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Row0 P2.0

Col0 P1.0

Col1 P1.1

Col2 P1.2

Keypad Enter

Keypad -

Keypad +

Row0 P2.0

Keypad 9

Row1 P2.1

Row1 P2.1 . . . Row14 P5.1

“ ‘

Row15 P2.0

Enter

PrtScr

è

F8

...

. . . Row14 P5.1 Row15 P2.0

1. Enter, PtrScr and è keys are pressed

Col0 P1.0

Col1 P1.1

Col2 P1.2

Keypad Enter

Keypad -

Keypad +

Row0 P2.0

Keypad 9

Row1 P2.1

“ ‘

Enter

PrtScr

è

F8

...

. . . Row14 P5.1 Row15 P2.0

Col0 P1.0

Col1 P1.1

Col2 P1.2

Keypad Enter

Keypad -

Keypad +

...

Keypad 9

“ ‘

Enter

PrtScr

è

F8

3. Driving Row15 detects è but it incorrectly detects F8

2. Driving Row14 detects Enter and PtrScr

Figure 5. "Ghost" Key Detection The software included in this application report detects potential "ghost" keys and does not report them to the host.

2.2

USB HID This application report uses the MSP430 application programming interface (API) stack found in the MSP430 USB Developers Package (MSP430USBDEVPACK). The stack is configured to work as a composite HID-HID interface with the first interface being a standard Keyboard and the second interface used as a DataPipe. One of the advantages of using this implementation, which using only HID interfaces, is that no drivers are required. Although the relevant code for the keyboard implementation uses the standard keyboard interface, the DataPipe interface was added to provide users with more flexibility and to facilitate customization. This interface can be used to send or receive any type of data to/from the host, so that the MSP430 microcontroller not only performs the job of a digital keyboard, but it can also be used to perform other jobs taking advantage of the same USB interface and the rest of the peripherals. Some examples include reading sensors using ADC and reporting to PC, controlling actuators using timer PWMs, etc. It should be noted that while the host OS interprets and uses the data from the standard keyboard interface without additional applications or drivers, in the case of the Datapipe interface, a host application is required. Texas Instruments provides an HID API which enables communication between a PC and a MSP430 microcontroller running the HID API stack. This HID API is available in executable format and source code in the MSP430 USB Developers Package (MSP430USBDEVPACK). The keyboard interface supports Boot protocol, which allows it to work with HID-limited hosts (such as some BIOS). VID and PID can be modified according to the particular application but the default code used for this example uses the values shown in Table 1. Table 1. VID/PID Used by the Device


VID

0x2047

PID

0x0401


5

Software

3

Software

3.1

Tools

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The software included in this application report was built and tested using: • IAR Embedded Workbench™ for MSP430 5.30.4 IDE • Code Composer Studio™ (CCS) 5.1.0 IDE

3.2

Software Implementation Figure 6 shows the software layers for the USB keyboard. Application USB Keyboard Comm Protocol

Keyboard Report

USB HID

DKS (Digital Keyscan)

USB API MSP430 Driverlib

UCS

PMM

ticktimer

Timer

GPIOs

DMA

USB

Hardware

Figure 6. USB Keyboard Software Modules Software is designed in a modular way, re-using existing TI libraries such as driverlib and the USB API and adding new modules from low-level drivers to application level. These modules include: • USB Keyboard Description Main application initializing the microcontroller, peripherals, and executing a loop checking and servicing the rest of the modules. Files Src\TI_USBKBD_main.c Flow Diagram

6



Software

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Initialize: PMM, UCS (clocks), GPIOs, Timers, USB, Timer,

USB Keyboard

Initialization

USB Active?

Y

USB Suspended?

N Disable DKS

Y Sleep

Y

Process RX data from HID0/HID1

N

Data received? N

Initialize DKS and KBD_Report modules

Y

First loop?

N

USB or Keyboard activity?

N

Y Wake MCU

Attend DKS module

Attend KBD_Report module

Y

Force Remote Wakeup

Pending tasks? N Sleep

N

USB, Timer or Keyboard activity?

Y

Figure 7. USB Keyboard Flow Diagram



7

Software

•

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Keyboard Report Description Handles the HID Keyboard report, adding and removing keys from the report depending on press/release events and sends the report to the USB Host. Files Src\TI_USBKBD_HIDKBD_report.c Src\Include\ TI_USBKBD_HIDKBD_report_public.h HID Keyboard Report Format Table 2. HID Keyboard Report Format Byte0

•

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

Right GUI

Right Alt

Right Shift

Right Ctrl

Left GUI

Left Alt

Left Shift

Left Ctrl

Byte1

Reserved

Byte2

Key_array[0]

Byte3

Key_array[1]

Byte4

Key_array[2]

Byte5

Key_array[3]

Byte6

Key_array[4]

Byte7

Key_array[5]

Communication Protocol Description Handles the HID custom interface, which is used to transfer data to/from an USB host. The current implementation shows a template that can be used for custom development. This module uses the HID-Datapipe as defined in the USB API included in MSP430 USB Developers Package (MSP430USBDEVPACK). Files Src\TI_USBKBD_comm_protocol.c Src\Include\ TI_USBKBD_comm_protocol_public.h HID Custom Interface Report Descriptor Table 3. Communication Protocol Report Descriptor Field

Size

Description

1 byte

The report ID of the chosen report (automatically assigned to 0x3F by the HID-Datapipe calls)

Size

1 byte

The number of valid bytes in the data field

Data

62 bytes

IN Report Report ID

Data payload OUT Report

1 byte

The report ID of the chosen report (must be assigned to 0x3F by the host)

Size

1 byte

The number of valid bytes in the data field

Data

62 bytes

Report ID

Data payload

Data Payload Protocol Table 4. Implemented Protocol

8

Field

Size

CMD

1 byte

Data

61 bytes

Description 1 = Toggle CAPS LED 2 = Toggle NUM LED Unused



Software

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•

DKS (Digital KeyScan) Description Handles the digital keyboard scanning, detecting key press/release events, and reporting them to the keyboard report module. Files Src\TI_USBKBD_DKS.c Src\Include\TI_USBKBD_DKS_public.h Flow Diagram DKS is initialized in “interrupt-column” mode by default if no key is pressed.

Digital KeyScan

Interrupt-column

polling Mode?

N

Key press detected?

Scan key matrix

Y Change to Polling mode

Release

None

Inactive timer N expired?

Key event?

Y

Press

Remove key from report

Change to Interrupt-Column mode

Y “Ghost” key? N

N

Key debounced?

Increment debounce counter

Y

Add key to report

Return

Figure 8. Digital Keyscan Flow Diagram



9

Software

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•

USB API / USB HID Description The MSP430 USB API stack is a software solution provided by Texas Instruments that includes support for: – Communications Device Class (CDC) – Human Interface Device class (HID) – Mass Storage Class (MSC) – Personal HealthCare Device Class (PHDC) This software solution, including detailed documentation, is available in the MSP430 USB Developers Package (MSP430USBDEVPACK). Files Src\USB_API\*.* Src\USB_config\*.* Src\USB_App\*.* Ticktimer Description Handles a general purpose interrupt timer that is used as a timebase, to wake-up the processor, and to trigger a new keyboard scan, among other functions. The ticktimer is implemented using TA0.0 with a default time base of 2 ms. Files Src\TI_USBKBD_ticktimer.c Src\Include\TI_USBKBD_ticktimer_public.h MSP430 Driverlib Description The Texas Instruments MSP430 Peripheral Driver Library (Driverlib) is a set of drivers that provide an easy mechanism to use the MSP430 peripherals. This software uses Driverlib to initialize the PMM and UCS modules. Source code and detailed documentation are available in MSP430Ware (www.ti.com/msp430ware). For simplicity purposes, this project includes only the pre-compiled libraries for IAR and CCS using a small memory model and header files. Files Src\ driverlib\*.h Src\ driverlib\driverlib_small_CCS.lib Src\ driverlib\driverlib_small_IAR.r43

•

•

3.3

Configuration and ScanCode Tables For modularity purposes and to allow for an easier optimization or upgrade, the USB keyboard software reserves some Flash sectors for constant tables that define some of the functionality of the application and define the ScanCode table. • Configuration Constant Table Description Contains the USB keyboard version and configuration constants defining the KeyScan functionality, such as debounce counter, ticktimer period, etc. Files Src\TI_USBKBD_SharedTables.c (declaration) Src\Include\TI_USBKBD_public.h (typedef) Declaration const USBKBD_config_const_t USBKBD_configconst_s

10



Software

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Location USBKBD_CONFIGCONST_SEGMENT (0xFC00-0xFDFF) Contents Table 5. Configuration Constant Table Field

•

Size

Description

MagicKey

4 bytes

Indicates the start of the table. 0xDEADC0DE is used by default.

Version

2 bytes

USB keyboard version in BCD format: 0x0101 - 1.0.1

ticktimer_div

2 bytes

TickTimer divider (based on ACLK): 66 represents a period of 66 / 32768 = ~2 ms

debounce_cycles

2 bytes

Number of debounce cycles in tick counts: 2 represents a debounce of 4 ms with Ticktimer = 2 ms

inactive_timeout

2 bytes

Number of tick counts before going to interrupt_column mode if no key is detected: 8 represents 16 ms with Ticktimer = 2 ms

ScanCode Table Description Contains the USB Keyboard scancode table, mapping each row and column to the corresponding value based on HID Usage Tables. Files Src\TI_USBKBD_SharedTables.c(declaration) Src\Include\TI_USBKBD_public.h(typedef) Declaration const USBKBD_scancodest_t USBKBD_scancodes_s

Location USBKBD_SCANCODES_SEGMENT (0xFA00-0xFBFF) Contents Table 6. ScanCodes Field

Size

MagicKey

4 bytes

keycode


Description Indicates the start of the table. 0xDEADC0DE is used by default.

128 bytes

Keycodes for each key in the following order: Row0,Col0 Row0,Col1 … Row0,Col7 Row1,Col0 Row1,Col1 … Row15,Col6 Row15,Col7


11

Hardware and Peripheral Usage

4

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Hardware and Peripheral Usage In addition to system modules (UCS, PMM), this keyboard implementation uses the peripherals shown in Table 7. Table 7. MSP430F550x/5510 Peripheral Usage Peripheral

Usage

USB

Communication with host (Composite HID-HID)

Timer_A0 (TA0.0)

TimerTick used as a time base to perform periodic polling, debounce, etc.

In addition to the circuitry required for USB and common functionality (reset, VCC, VSS, crystal, etc.), the USB keyboard uses the pins shown in Table 8. Table 8. MSP430F550x/5510 Pinout Usage

Columns

KSO0 KSO1 KSO2 KSO3 KSO4 KSO5 KSO6 KSO7 KSO8 KSO9 KSO10 KSO11 KSO12 KSO13 KSO14 KSO15

P2.0 P2.1 P2.2 P2.3 P2.4 P2.5 P2.6 P2.7 P3.0 P3.1 P3.2 P3.3 P3.4 P5.0 P5.1 P5.4

Rows

LEDs

KSI0 KSI1 KSI2 KSI3 KSI4 KSI5 KSI6 KSI7 LED0 (CAPS) LED1 (NUM)

P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 P4.7 P4.6

Schematics showing the implementation on the USB keyboard are found in Section 6.

5

Using the USB Keyboard When connected to a PC, the USB keyboard should be detected by the operating system and enumerated without drivers. Windows shows three devices in the Device Manager (see Figure 9). • Human Interface Devices – USB Human Interface Device: Standard keyboard in intf0 (MI_00) – USB Human Interface Device: Custom interface in intf1 (MI_01) • Keyboards – HID Keyboard Device: Standard keyboard in intf0 (MI_00)

12



Using the USB Keyboard

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Figure 9. USB Keyboard in Windows Device Manager The keyboard can now be tested and used as a standard keyboard. In addition to the regular key functionality, the custom interface can be tested using the MSP430 HID USB Application following these steps (see Figure 10): 1. Select the VID and PID (default: VID = 0x2047, PID = 0x0401). 2. Click Set VID PID. 3. Click Connect. 4. The LED should turn green. 5. Write one of the commands in the Send & Receive field. 6. Observe the response from the USB keyboard.



13

Using the USB Keyboard

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3

2

4

1 5

6

Figure 10. Testing the HID Custom Interface The MSP430 HID USB Application is available in the MSP430 USB Developers Package (MSP430USBDEVPACK).

5.1

Performance The usual response time for keyboards is approximately 5 to 50 ms. While this depends on different factors such as the mechanical implementation of the keyboard, USB bus load, etc., by using this software, developers have more flexibility to customize the application according to their needs. Whether response time, price, or power consumption is the most important requirement, parameters such as debounce time, polling scan rate, USB polling interval, and microcontroller internal frequency can be adjusted to meet particular requirements. One important factor affecting the response time is the polling rate, which defines the time required to scan all keys. While a key press is detected in a few cycles in column-interrupt mode, the algorithm to recognize the particular pressed key, debounce it, discard "ghost" keys, etc. can take more cycles. During bench tests, this implementation was measured to take ~1870 cycles (which is equivalent to ~233 µs at 8 MHz) for the first pressed key and ~520 cycles (~65 µs at 8 MHz) for each additional pressed key.

5.2

Memory Footprint The following memory footprint was obtained using IAR Embedded Workbench 5.30.4 using the maximum optimization level: Code: 7626 Bytes Constants: 1096 Bytes Data: 679 Bytes

14



Schematics

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6

Schematics

R8

R11 1M 10p C35 10p C36

KSI5

LED1

LED0

R14

KSI6

4.7M R15

NC0

R16

IC7

KSI7

4.7M

4.7M

GND

IO1 VCC

6

2

IO2

IO4

5

3

GND IO3

4

TPD4E004

GND GND

4.7u C39

VBUS

D-

USB1

D- 2

1

D+ 3

GND

D+

4

SHIELD

SBW/Power

SBW_VCC

JP3

14 12 10 8 6 4 2

JTAG1

JP1

int

2

LL103A D3

1 2 3

ext

1 2

DVCC1

13 11 9 7 5 3 1

SBWTCK

SBWTDIO

VBUS

48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33

GND IN OUT 1

GND NR/FB 3

EN

C20

Q1G$1

3

2

Q1G$2 4

C3

47pF

4MHz

XT2

1

C4 47pF

GND

220n

VBUS_LDO

4.7uF

XT2OUT

XT2IN

C21

10nF

GND

220n C38

8

4

C11 100nF

GND

V18 VUSB VBUS PU.1/DM PUR PU.0/DP VSSU C33

5

LED0 LED1

DVCC1 KSO12 KSO11 KSO10 KSO9 KSO8 KSO7

Digital Keyboard

1uF

GND

R42

JP6 C19

330R

SBWTCK XT2OUT XT2IN AVSS V18 VUSB VBUS PU.1/DM PUR PU.0/DP GND

1 VUSB_VCC

VCC1 SBW_VCC

470nF

VBUS_LDO3

SBWTDIO

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

GND

VCC1

R5 47K

GND

GND

SHIELD1

C8

KSO13 KSO14

KSO15 GP

C9

GND

KSO0 KSO1 KSO2 KSO3 KSO4 KSO5 KSO6

KSI0 KSI1 KSI2 KSI3 KSI4 KSI5 KSI6 KSI7

TP 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

5

6

C13 100nF

33k

DNP

LL103A D2

R36

GND

+ 10uF/6,3V

VBUS

0.1u C40

GND

C5 C7

100nF

AVCC GND

1

GND

AVCC

DVCC1

C10

GND

10uF/6,3V +

R35 27R

R13 4.7M

2

R34 27R

KSI4

4.7M

GND

R19 330R

R18 330R

KSI3

4.7M

R10

1

GND GND GND

KSI2

R7

100R

S3

USB Interface

R6 4.7M

R33 1.4k PUR PU.0/DP PU.1/DM

KSI1

4.7M

VUSB

R3

GND

Digital Keys

KSI0

LED1

GP KSO7 KSO0 KSI1 KSI7 KSO9 KSI6 KSI5 KSO3 KSI4 KSI2 KSO1 KSI3 KSI0 KSO13 KSO5 KSO2 KSO4 KSO8 KSO6 KSO11 KSO10 KSO12 KSO14 KSO15

Digital Connector

LEDs

GND LED0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

P$1 P$2 P$3 P$4 P$5 P$6 P$7 P$8 P$9 P$10 P$11 P$12 P$13 P$14 P$15 P$16 P$17 P$18 P$19 P$20 P$21 P$22 P$23 P$24 P$25 P$26 P$27 P$28 P$29 P$30

A

GND

VUSB_VCC

GND

D4 LL103A

Figure 11. Schematics



15

References

7

References 1. 2. 3. 4. 5. 6.

16

www.ti.com

USB HID specification (www.usb.org/developers/devclass_docs/HID1_11.pdf) MSP430x5xx/MSP430x6xx Family User's Guide (SLAU208) MSP430F550x/MSP430F5510 Mixed Signal Microcontroller data sheet (SLAS645) MSP430 USB Developers Package (MSP430USBDEVPACK) (www.ti.com/tool/msp430usbdevpack). MSP430Ware (www.ti.com/msp430ware) Implementing an Ultralow-Power Keypad Interface With the MSP430 (SLAA139)



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USB Keyboard Using MSP430 Microcontrollers

USB Keyboard Using MSP430 Microcontrollers

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