CypressUSB教程第5讲.pptVIP

Lecture 5 Agenda Suspend/Resume How it works How to code it A Gotcha Keil Debug tip—the Watch window HID Introduction Enumeration code Start safely Use control panel to test: Get_Descriptor: Device Get_Descriptor: Interface Get_Descriptor: String Suspend/Resume Suspend-Resume Mechanism (TRM Ch.11) ‘Suspend’ ‘Suspend’ Code ‘Resume’ ‘Resume’ Code ‘Resume’ Code Complete example in ‘suspend.c’ sofint.c with enhancements: Updates digit count rate from EP2OUT Adds suspend/resume code Three code modules suspend.c int2jmp.a51 wuisr.c Suspend/Resume Issue There is a problem with suspend.c After ‘resume’, the next IN-2 request hangs Demonstration What’s Happening USB bus reset un-arms all IN endpoints TRM 6, Section 10.5: “After a USB bus reset, the EZ-USB core ‘unarms’ all Bulk IN endpoints. Data loaded by the 8051 into an IN endpoint buffer remains there, and the 8051 firmware can either re-send it by loading the endpoint byte count register to re-arm the transfer, or send new data by re-loading the IN buffer before re-arming the endpoint.” A solution Re-arm IN2 whenever there’s a USB reset This preserves the data already loaded into the IN endpoint buffer Demonstration Final Suspend/Resume Note No apparent consistency from PC to PC in handling suspend Most variation seen in laptops How (and if) they suspend How (and if) they resume KILLER: Some turn off Vbus during suspend VERY hard to execute ‘resume’ code if we are bus-powered and the power goes away… Keil Debug Tip Keil Debugging Tip Using the Watch Window Display all symbols This table is built from compile of your code (w. includes) Set WatchPoints Watch window updates when code execution stops Where to find tools help C:\Cypress\USB\uV2_4k\keil\C51\HLP A51.pdf is Assembler Reference Manual C51.pdf is C Compiler Reference Manual C:\Cypress\USB\Doc\Keil Doc EZ-USB Control Panel Help/Contents and Tutorial, and Help/Control Panel User Guide HID Part 1 HID Class Built into Windows 98 (or later) No need to write a driver!