Resource usage
Memory footprint
emUSB-Device is designed to fit many kinds of embedded design requirements. Several features can be excluded from a build to get a minimal system. The code size depends on the API functions called by the application. The code was compiled with the SEGGER compiler for a Cortex-M4 CPU with size optimization. Note that the values are only valid for an average configuration.
The following table shows the approximate ROM and RAM requirements of emUSB-Device
| Component | ROM | RAM | Note |
|---|---|---|---|
| USB core | 5.5 KByte | 1.0 KByte | |
| Bulk | 2.0 KByte | 0.1 KByte | |
| CDC | 1.3 KByte | 0.1 KByte | |
| HID | 1.5 KByte | 0.1 KByte | |
| MSD | 4.8 KByte | 0.5 KByte | + size of file system + configurable sector buffer of minimum 512 bytes (RAM) |
| MTP | 14.4 KByte | 1.7 KByte | + size of file system + configurable file data buffer of minimum 512 bytes RAM) + configurable object buffer (typically 4 kBytes RAM) |
| Printer | 1.0 KByte | 2.1 KByte | |
| RNDIS | 5.3 KByte | 1.5 KByte | + size of the IP stack |
| ECM | 2.8 KByte | 0.2 KByte | + size of the IP stack |
| IP-Over-USB | 7.1 KByte | 1.7 KByte | + size of the IP stack |
| VirtualMSD | 8.1 KByte | 1.0 KByte | + heap of minimum 1700 bytes RAM |
| DFU | 1.0 KByte | 0.0 KByte | |
| AUDIO | 3.6 KByte | 0.2 KByte | + static configuration data |
| MIDI | 1.8 KByte | 0.0 KByte | |
| CCID | 1.2 KByte | 0.0 KByte | |
| USB target driver | 1.3 - 3.6 KByte | 0.0 - 7.6 KByte |
Additionally 64, 512 or 1024 Byte (for full-speed, high-speed and SuperSpeed devices, respectively) of RAM are necessary for each OUT-endpoint as a data buffer. This buffer is assigned within the application.