NXP Semiconductors LPC5500 Series Reference manual

1 Introduction
1.1 Dual-USB introduction
LPC4300 series, LPC54000 series, and LPC5500 series, contain the feature
called dual-USB interface. The feature helps to set the LPC portfolio apart from
its competitors. Most of these parts, such as, LPC5500 series, has High-Speed
(HS) USB and Full-Speed (FS) USB with on-chip PHY. The dual-USB parts
provide up to 480 Mbit/s throughput, which can meet high-speed data transfer
requirement for any MCU application.
Unlike the competitors with only FS USB PHY, the dual-USB parts contain both
FS and HS on-chip PHY, which can greatly reduce design complexity.
Figure 1. LPC5500 series block diagram
Contents
1 Introduction......................................1
1.1 Dual-USB introduction................. 1
1.2 USB history, standard, and speed
definition.......................................2
2 Why high-speed USB......................3
2.1 Lower latency in interrupt transfer
.....................................................3
2.2 Larger packet length.................... 3
2.3 Example for USB HID mouse
application....................................4
3 Getting started with USB demo with
SDK.................................................6
3.1 USB stack configurations.............8
3.2 Hardware connection...................8
3.3 USB device example....................8
4 Hardware design........................... 10
5 Summary.......................................12
6 Reference......................................12
7 Revision history.............................12
AN13449
Introduction to Dual USB port on LPC5500/LPC54600 Series
Rev. 0 — 11 November 2011 Application Note

Figure 2. LPC54600 series block diagram
The dual-USB interface enables numerous interesting and useful applications, as seen on LPC5500 MCU Series.
1.2 USB history, standard, and speed definition
USB Implementers Forum (USB-IF), a non-profit organization that maintains the USB documents and compliance programs,
regulates the USB. The USB specification has undergone multiple revisions.
1. USB 1.0 was finalized in January 1996. The original specification only included supports for two speeds:
• Low-Speed (LS): Supported 1.5 Mb/s
• Full-Speed (FS): Supported 12 Mb/s
2. USB 1.1 was developed in 1998. In this revision, some clarifications and improvements were added to the USB 1.0
specification.
3. USB 2.0 was released in April 2000 and the next major change occurred. In this revision, a new speed, High-Speed
(HS), was added to the specification. The speed was up to 480 Mb/s. This specification revision is backward-compatible
with USB 1.1 and 1.0.
4. USB 3.0 was announced in November 2008 and the same backward compatibility was maintained. This revision
provides the speed up to 5 Gb/s. With USB 3.0 came a new physical connector as well.
5. More recently, USB-IF announced the plans for USB 3.1, when the speed will increase up to 10 Gb/s.
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Introduction
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Table 1. USB revisions
Standard Also known as Year introduced Max. data transfer speed Cable length
USB1.1 Full Speed USB 1998 12 Mbps 3 m
USB2.0 Hi-Speed USB 2000 480 Mbps 5 m
USB3.2 Gen1 USB3.0/USB3.1 SuperSpeed 2008 5 Gbps 3 m
USB3.2 Gen2 USB3.1 Superspeed+ 2013 10 Gbps 3 m
2 Why high-speed USB
The performance enhancement of HS USB depends on new features on USB 2.0 standard.
2.1 Lower latency in interrupt transfer
1 ms frame rate, in FS/LS USB, is used for a number of purposes, such as, scheduling access to the bus and working as a
timing reference for interrupt and isochronous transfers. For HS, a higher frame rate was introduced, while still maintaining a
relationship with the existing 1 kHz rate. HS uses the Microframes which are 125 us long (eight Microframes per millisecond).
The correspondence with the 1 ms frame numbering is maintained in the HS SOF packets by repeating each frame number in
eight successive Microframes . HS possibly specifies up to three isochronous or interrupt transfers per Microframes . FS, with one
transfer per frame, provides maximum isochronous or interrupt transfer rate of 192 Mb/s.
Figure 3. HS USB uses Microframes to increase throughput
2.2 Larger packet length
See Table 2 for LS, FS, and HS maximum packet size.
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Table 2. Packet size
Transfer type
Max. packet size
LS FS HS
Control 8 8, 16, 32, 64 64
Bulk — 8, 16, 32, 64 512
Interrupt Up to 8 up to 64 Up to 1024
Isochronous —- up to 1023 up to 1024
2.3 Example for USB HID mouse application
Most on-market USB mouses use 125 Hz update rate which can meet general requirements. But when entering the field of e-sport
gaming mouse, 125 Hz update rate is not fast enough.
USB mouse uses USB HID class (interrupt transfer). Figure 4 shows a typical on-market FS USB mouse latency.
A1 is the time when the mouse button is pressed and A2 is the time when USB sends the HID report to PC. As seen in Figure 4,
the latency can be large as 6 ms (125 Hz report rate). In worst scenario, the latency can reach 8 ms.
Figure 4. FS HID mouse latency between button press and USB send data
With the same test for HS USB, the report rate configures to maximum 8 kHz and the latency is 119 us. In worst scenario, the
latency is only 125 us.
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Why high-speed USB
Introduction to Dual USB port on LPC5500/LPC54600 Series, Rev. 0, 11 November 2011
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Figure 5. HS HID mouse latency between button press and USB send data
The interrupt transfer interval can also be seen from USB data lines signal:
• In FS USB: the minimum interrupt transfer interval is 1 ms.
• In HS USB: the interrupt transfer minimum interval can reach 41.6 us (125/ 3 us, see Lower latency in interrupt transfer).
In most use cases, 125 us interval is fast enough.
Figure 6. USB data line signal: FS interrupt transfer minimum interval: 1 ms
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Why high-speed USB
Introduction to Dual USB port on LPC5500/LPC54600 Series, Rev. 0, 11 November 2011
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Figure 7. USB data line signal: HS interrupt transfer interval: 125 us
3 Getting started with USB demo with SDK
This section provides a hands-on guide to help you start to evaluate USB demo with SDK. Let us take the LPC55S69 as example.
LPC55S69 EVB board has four USB mini connectors: P10, P5, P9, P6.
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Getting started with USB demo with SDK
Introduction to Dual USB port on LPC5500/LPC54600 Series, Rev. 0, 11 November 2011
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Figure 8. LPC55S69 EVB board
Table 3. LPC55S69 EVB board
Circuit reference Description
P10 LPC55Sxx USB0 (FS) micro AB port connector
P9 LPC55Sxx USB1 (HS) micro AB port connector
P6
Link2 Debug Probe connector
Micro USB type B connection for the on-board Link2 Debug Probe
Do not use this connection when using an external Debug Probe.
NOTE
P5
External +5 V power
Micro USB connection for power to the LPC55Sxx target and peripheral circuitry (excluding
Link2 Debug Probe)
• For USB device demo, P5 is not used.
• For USB host demo, P5 must be powered.
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Getting started with USB demo with SDK
Introduction to Dual USB port on LPC5500/LPC54600 Series, Rev. 0, 11 November 2011
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For more details about this board, see Getting Started with the LPC55S69-EVK Evaluation Board.
3.1 USB stack configurations
3.1.1 Enable/disable dual USB ports
To switch between USB0 (FS) and USB1 (HS). Change the macro in usb_device_config.h.
• To enable/disable USB1, change USB_DEVICE_CONFIG_LPCIP3511HS to 1/0.
• To enable/disable USB0, change USB_DEVICE_CONFIG_LPCIP3511FS to 1/0.
3.2 Hardware connection
• For USB0 (FS) demo, connect P10 to PC.
• For USB1 (HS) demo, connect P9 to PC.
• To download and debug firmware, connect P6 to PC.
• If you have three USB cables, it is OK to connect all three USB connectors to PC.
• Suggest connecting USB port to PC USB port directly, not via USB hub.
3.3 USB device example
3.3.1 HID mouse example
Demo project location:
\boards\lpcxpresso55s69\usb_examples\usb_device_hid_mouse
The HID transfer interval is controlled in the bInterval filed in the endpoint descriptor.
For FS/LS interrupt endpoints, the value of this field may be from 1 to 255.
• Change the FS_HID_MOUSE_INTERRUPT_IN_INTERVAL value in usb_device_descriptor.h.
For example:
#define FS_HID_MOUSE_INTERRUPT_IN_INTERVAL (0x02U)
Change the FS HID transfer interval to 2 ms.
For HS interrupt endpoints, the bInterval value is used as the exponent for a 2 ^(bInterval-1) value. This value must be from
1 to 16.
• Change HS_HID_MOUSE_INTERRUPT_IN_INTERVAL value in usb_device_descriptor.h.
For Example, a bInterval of 6 means a period of (2^(6-1)) = 32 *125 us = 4 ms.
#define HS_HID_MOUSE_INTERRUPT_IN_INTERVAL (0x06U) /* 2^(6-1) = 4ms */
Change the high-speed HID transfer interval to 4 ms.
If the bInterval value changes, the mouse movement speed changes too. Also, when using HS ports, you can configure to
bInterval 1 to reach 125 us frame interval.
• For FS ports, the minimum frame interval is 1 ms.
• For HS ports, the minimum frame interval is 125 us.
See Example on USB gaming mouse for details.
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Getting started with USB demo with SDK
Introduction to Dual USB port on LPC5500/LPC54600 Series, Rev. 0, 11 November 2011
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3.3.2 MSC example
Demo project location:
\boards\lpcxpresso55s69\usb_examples\usb_device_msc_ramdisk
Change the macro:
#define TOTAL_LOGICAL_ADDRESS_BLOCKS_NORMAL (360U)
Then, RAM disk size can meet the minimum requirement of PC MSC test software: CrystalDiskMark.
• FS USB: Buck transfer speed can reach 1.14 MB/s. See Figure 9 for test result.
Figure 9. FS USB RAM disk test speed
• HS USB: Buck transfer speed can reach 24 MB/s. See Figure 10 for test result.
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Getting started with USB demo with SDK
Introduction to Dual USB port on LPC5500/LPC54600 Series, Rev. 0, 11 November 2011
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Figure 10. HS USB RAM disk test speed
For details, see Example for USB HID mouse application.
4 Hardware design
Both FS and HS USB ports contain on-chip PHY to make the schematic design much simpler. Figure 11 and Figure 12 are the
schematic reference for FS and HS ports.
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Hardware design
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