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PDF TB055 Data sheet ( Hoja de datos )
| Número de pieza | TB055 | |
| Descripción | PS/2 to USB Mouse Translator | |
| Fabricantes | Microchip Technology | |
| Logotipo |  |
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TB055
PS/2® to USB Mouse Translator
Author: Reston Condit
Microchip Technology Inc.
OVERVIEW
This Technical Brief details the translation of a PS/2®
mouse to a USB mouse using the PIC16C745/765. The
PIC16C745/765 is Microchip’s low-speed USB micro-
controller. All of the USB descriptors for the mouse
translator are listed in the tables in Appendix A:
“Device Descriptors”. A detailed byte-by-byte
description is given for each descriptor to assist USB
peripheral designers in understanding USB descrip-
tors. For the basics of USB descriptors, refer to TB054,
“An Introduction to USB Descriptors with a Game Port
to USB Game Pad Translator Example”.
IMPLEMENTATION
Hardware
The PS/2 port is a 6-pin DIN. Only four pins are used:
• Ground
• Power
• Clock
• Data
The power and ground pins are tied directly to VDD and
VSS of the microcontroller. The clock and data pins are
connected to RC0 and RC1, respectively, via current
limiting resistors. The clock is driven by the PS/2
mouse regardless of the direction of the transaction.
Figure 1 shows the complete system.
Note:
This Technical Brief is the second in a
series of five technical briefs. This series is
meant to familiarize developers with USB.
For the best understanding of USB, read
the briefs in order: TB054, TB055, TB056,
TB057 and TB058.
FIGURE 1:
PS/2® TO USB MOUSE TRANSLATOR HARDWARE DIAGRAM(1)
C1(2)
PIC16C745/765
C2(2)XTAL
OSC1
6 MHz
VUSB
C3 200 nF
Host
PS/2®
OSC2
R1 1.5k
Female
100Ω
USB Cable
D- D-
6
4
5
3
5
3
Clock
Data
4
21
1
RC0
RC1
D+
VSS*
VDD*
C4
0.1 µF
D+
GND
+5 VDC
Note 1: There are two VSS and VDD pins on PIC16C765.
2: C1 and C2 values selected according to crystal load capacitance.
2004 Microchip Technology Inc.
DS91055C-page 1
1 page  
TB055
APPENDIX A: DEVICE
DESCRIPTORS
Chapter 9 of the USB Specification, V 1.10, defines the
standard descriptors (Device, Configuration, Interface,
Endpoint and String Descriptors.) The HID Class
Definition defines the HID descriptors (HID and
Report).
TABLE 3: DEVICE DESCRIPTORS
Offset
Field
Size
0 bLength
1 bDescriptorType
2 bcdUSB
4 bDeviceClass
1
1
2
1
5 bDeviceSubClass
1
6 bDeviceProtocol
1
7 bMaxPacketSize0
8 idVendor
10 idProduct
12 bcdDevice
14 iManufacturer
1
2
2
2
1
15 iProduct
1
16 iSerialNumber
1
17 bNumConfigurations
1
Description
Size of descriptor in bytes
Descriptor type (DEVICE = 1)
USB specification release (Ver 1.10 = 0x0110)
Class code (this field is zero if every interface specifies
its own class information)
Subclass code (if the class code is zero this must be
zero)
Protocol code (zero if it does not use a class-specific
protocols on a device level)
Maximum packet size (eight for low speed)
Vendor ID (assigned by the USB-IF)
Product ID (assigned by the manufacture)
Device release number in binary-coded decimal
Index of string descriptor describing manufacturer
(String 1 is “Microchip”)
Index of string descriptor describing product (String 2 is
“PIC16C745/765 USB Mouse”)
Index of string descriptor describing the serial number
(none)
Number of possible configurations
Value for
Mouse
0x12
0x01
0x0110
0x00
0x00
0x00
0x08
0x04D8
0x0001
0x0441
0x01
0x02
0x00
0x01
TABLE 4: CONFIGURATION DESCRIPTOR
Offset
Field
Size
Description
0 bLength
1 bDescriptorType
2 bTotalLength
4 bNumInterfaces
5 bConfigurationValue
6 iConfiguration
7 bmAttributes
8 bMaxPower
1 Size of descriptor in bytes
1 Descriptor type (CONFIGURATION = 2)
2 Total length of data returned for this configuration (For
the mouse example this is the combined length of the
configuration, interface, HID and endpoint descriptors)
1 Number of interfaces supported by this configuration
1 Value to use as an argument to the Set Configuration()
request to select this configuration
1 Index of string descriptor describing this configuration
(String 4 is “Cfg1”)
1 Configuration characteristics
Bit 7
Always one
Bit 6: Self-powered
Bit 5: Remote wake-up
Bits 4..0: Zero
1 Maximum power consumption expressed in 2 mA units
(in this case 50 = 100 ma)
Value for
Mouse
0x09
0x02
0x0022
0x01
0x01
0x04
0xA0
0x32
2004 Microchip Technology Inc.
DS91055C-page 5
5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet TB055.PDF ] | |
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