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USB Component
Version 5.1
MDK-Professional Middleware for USB Device and Host
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This section describes the resource requirements of the USB component. The actual requirements depend on the components used in the application and the configuration of these components.
The following section documents the requirements for the USB Device Component.
The USB Device component uses CMSIS-RTOS threads. Each instance of a component starts its own threads, for example two HID instances start two threads with the name: USBD_HID0_Thread, USBD_HID1_Thread. The thread execution starts with USBD_Initialize. All threads execute with priority osPriorityAboveNormal on an user-provided stack.
The following table lists the components, number of threads executed along with thread name, the default stack size, and the configuration file with OS Resource Settings for stack size adjustments.
Component | Threads / Thread Name | Default Stack Size | Configuration File |
---|---|---|---|
::USB:Device | 1 / USBDn_CoreThread | 512 Bytes | USBD_Config_n.c |
::USB:Device:ADC | 1 / USBD_ADCn_Thread | 512 Bytes | USBD_Config_ADC_n.c |
::USB:Device:CDC | 2 / USBD_CDCn_Bulk_Thread, USBD_CDCn_Int_Thread | 512 Bytes | USBD_Config_CDC_n.c |
::USB:Device:Custom Class | 1...15 / USBD_CustomClassn_EPm_Thread | 512 Bytes | USBD_Config_CustomClass_n.c |
::USB:Device:HID | 1 / USBD_HIDn_Thread | 512 Bytes | USBD_Config_HID_n.c |
::USB:Device:MSC | 1 / USBD_MSCn_Thread | 512 Bytes | USBD_Config_MSC_n.c |
n is instance number, m is Endpoint number 1...15
For the USB Device component, the number of threads and thread stack size requirements are calculated as follows:
With default stack size of 512 Bytes, the Total stack size is Number of Threads * 512 Bytes. When the default OS Resource Settings are modified, the changes need to be considered for the calculation of the Total stack size.
Examples (with default stack size 512 Bytes):
The thread requirements need to be reflected in the CMSIS-RTOS configuration. Refer to the CMSIS-RTOS Reference for further details.
For CMSIS-RTOS RTX, the threads requirements are configured in the RTX_Conf_CM.c
file located in the CMSIS components.
Option (under section Thread Configuration) | Increase Value by |
---|---|
Number of concurrent running threads | + Number of Threads |
Number of threads with user-provided stack size | + Number of Threads |
Total stack size [bytes] for threads with user-provided stack size | + Total stack size |
The ::USB:Device:HID component requires User Timers to be selected. The Timer Thread Stack is commonly used by all threads working with User Timers. Depending on the application and the further usage of the timers, the Timer Thread stack size needs to be increased accordingly.
The USB Device Core is called by interrupt service routines (ISR) from the USB Device Driver. The stack requirements for the ISR are typically less than 512 Bytes. The total stack space required for ISR depends on the interrupt nesting and therefore on the priority settings of these ISR. The stack requirements for ISR is configured in the startup_device.s file located in the Device components.
Option (under section Stack Configuration) | Increase Value by |
---|---|
Stack Size (in Bytes) | + 512 for USB Device Driver |
User code that calls API functions of the USB Device Component should have a mimimum of 512 Bytes of stack space available. Since API functions are frequently called from threads, the thread stack size should be at least 512 Bytes.
The following table shows the memory requirements for read-only (Flash) and read-write (RAM) memory. These numbers may be used to estimate the total size requirements of the application, but the actually numbers depend on compiler optimizations and target processor and may be therefore slightly different.
Component | RO Memory [Bytes] | RW Memory (Data) [Bytes] |
---|---|---|
::USB:Core | 5.0 k | < 200 |
::USB:Device:ADC | 1.2 k | < 40 + Subframe Size (configured in USBD_Config_ADC_n.h) |
::USB:Device:HID | 2.6 k | < 70 + Report Sizes (configured in USBD_Config_HID_n.h) |
::USB:Device:MSC | 4.0 k | 96 + Bulk Buffer Size (configured in the USBD_Config_MSC_n.h) |
::USB:Device:CDC | 2.1 k | < 40 + Send/Receive Buffer Size (configured in the USBD_Config_CDC_n.h) |
::USB:Device:Custom Class | 2.4 k | < 30 |
USB Device Driver | 1 .. 4 k | 0.5 .. 4 k |
The following requirements can be changed in the startup_device
.s file (below the Device component class).
Type | Size | Description |
---|---|---|
Stack Size (in Bytes) | min. 6KB | Depends on functionality used |
Heap Size (in Bytes) | min. 334 Bytes |
State your requirements here.
The component uses CMSIS-RTOS functionality and defines the following threads.
For CMSIS-RTOS RTX, the following requirements can be changed in the RTX_Conf_CM.c
file (below the CMSIS component class). For corresponding settings, please refer to the user's guide of your selected RTOS.
Option | Value | Note |
---|---|---|
Number of concurrent running threads | ||
Default Thread stack size [bytes] | ||
Main Thread stack size [bytes] | ||
Number of threads with user-provided stack size | ||
Total stack size [bytes] for threads with user-provided stack size |