Cypress EZ-USB FX2LP User Manual

Application Note 21 of 42 001-65209 Rev.*I
2021-03-19
Getting Started with FX2LP™
FX2LP Development Tools
• dscr.a51 is an assembly language file containing the data necessary to enumerate the USB device. The file
comprises table data in the form of .db (define byte) statements. You edit this file to customize items such
as VID/PID and descriptive strings for your design.
• USBJmpTb.OBJ is a jump table required by the FX2LP architecture, never requiring modification.
• EZUSB.LIB contains a library of useful FX2LP functions, mostly dealing with I
2
C communication. The source
code is included with the FX2LP DVK in the Target\Lib\LP subfolder.
main() {
TD_init();
Enable Interrupts
while(1)
{
if(GotSUD)
TD_Poll();
}}
fw.c
Descriptors
Handle
EP0
dscr.a51
GET_DESCRIPTOR
bulkloop.c
BOOL DR_SetConfiguration(void)
BOOL DR_GetConfiguration(void)
BOOL DR_Set_Interface(void)
BOOL DR_Get_Interface(void)
TD_Init()
{….}
TD_Poll()
{....}
void ISR_EP2inout(void)
void ISR_EP6inout(void)
void ISR_Sof(void)
Figure 22 USB Firmware Framework Structure
Figure 22 shows how the code modules fit together.
Fw.c contains the main function. It performs much of the USB maintenance, such as enumeration, and it calls
specifically-named external functions in the application code (bulkloop.c) whenever customization is required.
Fw.c mostly does not require your modification. After performing various housekeeping steps, it calls an
external function called TD_init, which you provide in bulkloop.c. (The prefix TD stands for “Task Dispatcher”.)
Then it enters an endless loop that checks for arrival of SETUP packets over CONTROL endpoint 0. The loop also
checks for the USB suspend event, but this is not used by the bulkloop application. Every time through the loop,
it calls the external TD_Poll function which you provide in bulkloop.c. In this application the TD_Poll function
does the work of looping PC endpoint data through FX2LP.
Every USB peripheral receives two types of requests over its CONTROL endpoint: enumeration and operational.
Enumeration
When a USB device is attached, the host PC sends multiple GET_DESCRIPTOR requests to discover the device
type and its requirements as part of a process called enumeration. The fw.c code intercepts these requests and
handles them using the values stored in the dscr.a51 file.
An advantage of using the USB Frameworks is that the code has been tested and verified to pass USB “Chapter
9” requirements. Chapter 9 refers to the chapter in the USB Specification that deals with device requests (over
EP0) and their proper responses.
Operational
Wherever the user code is needed, fw.c calls a specifically-named external function with the DR prefix (Device
Request) that you provide in the bulkloop.c file. For a simple application such as bulkloop, there is only one
configuration and one interface, so the two DR_Set-Get function pairs in Error! Reference source not found. s

Cypress EZ-USB FX2LP Specifications

General

Brand	Cypress
Model	EZ-USB FX2LP
Category	Controller
Language	English