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Networking over USB
- A DaVinci DM355 EVM (USB peripheral device)
- A computer running Linux (USB Host)
- TI DaVinci LSP kernel source
- A USB A to mini-B cable
Configuring the EVM Hardware
This section will cover how to configure the DaVinci hardware as a USB peripheral device.
- J9 jumpered
- J10 un-jumpered
Connect the USB cable to a standard USB A socket. Connect the USB Mini-B end of the cable to the DM355 EVM (J5).
< > Support for Host-side USB <M> Inventra USB Highspeed Dual Role Controller Support --- DaVinci 644x USB support Driver Mode (USB Peripheral (gadget stack)) ---> [*] Disable DMA (always use PIO) (0) Logging Level (0 - none / 3 - annoying / ... ) --- NOTE: USB_STORAGE enables SCSI, and 'SCSI disk support' may also be needed; see USB_STORAGE Help for more information USB Gadget Support --->
USB Gedget Support:
<M> Support for USB Gadgets [*] Debugging information files USB Peripheral Controller (Inventra (M)HDRC USB Peripheral) ---> USB Gadget Drivers < > Gadget Zero (DEVELOPMENT) <M> Ethernet Gadget [*] RNDIS support (EXPERIMENTAL) < > Gadget Filesystem (EXPERIMENTAL) < > File-backed Storage Gadget < > Serial Gadget
Connect the DM355 EVM to the Host PC via the USB cable.
Set the DM355 up as a Network Gadget:
modprobe musb_hdrc use_dma=n modprobe g_ether ifconfig usb0 10.0.0.2 up
Output from dmesg on the DM355 EVM:
musb_hdrc: version 2.2a/db-0.4.8 [cppi-dma] [peripheral] [debug=0] Registering platform device 'musb_hdrc'. Parent at platform musb_hdrc: ConfigData=0x06 (UTMI-8, dyn FIFOs, SoftConn) musb_hdrc: MHDRC RTL version 1.300 musb_hdrc: setup fifo_mode 4 musb_hdrc: hw_ep 0shared, max 64 musb_hdrc: hw_ep 1tx, max 512 musb_hdrc: hw_ep 1rx, max 512 musb_hdrc: hw_ep 2tx, max 512 musb_hdrc: hw_ep 2rx, max 512 musb_hdrc: hw_ep 3tx, max 512 musb_hdrc: hw_ep 3rx, max 512 musb_hdrc: hw_ep 4tx, max 512 musb_hdrc: hw_ep 4rx, max 256 musb_hdrc: USB Peripheral mode controller at c886e000 using PIO, IRQ 12 usb0: Ethernet Gadget, version: Equinox 2004 usb0: using musb_hdrc, OUT ep1out IN ep1in STATUS ep2in usb0: MAC de:b8:d7:c3:54:27 usb0: HOST MAC 66:ae:d1:47:3a:32 usb0: RNDIS ready usb0: high speed config #3: 100 mA, Ethernet Gadget, using CDC Ethernet
The Host PC (running Linux) should have automatically loaded the necessary drivers for the USB CDC class: cdc_ether and usbnet.
Bring the network up and ping the USB device:
ifconfig usb0 10.0.0.1 up ping 10.0.0.2 PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data. 64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=7.49 ms 64 bytes from 10.0.0.2: icmp_seq=2 ttl=64 time=0.390 ms
Output from dmesg on the Host PC:
usb 7-4: new high speed USB device using ehci_hcd and address 14 usb 7-4: configuration #3 chosen from 2 choices usb0: register 'cdc_ether' at usb-0000:00:1a.7-4, CDC Ethernet Device, 66:ae:d1:47:3a:32
Netcat is a very useful tool for sending and receiving data over the network.
Setup the DM355 EVM to receive data from the Host PC:
nc -l -p 3000 > /dev/null
Create a test file on the Host PC and send this over the network to the USB device:
dd if=/dev/urandom of=100M-random.data bs=1M count=100 time ( cat 100M-random.data | nc -q 0 10.0.0.2 3000 ) real 1m8.690s user 0m0.012s sys 0m0.404s
Therefore the throughput = ( 100MB * 8 / 68 sec ) = 11.76 Mbps
- The g_ether driver does not seem to work when musb_hdrc is using DMA, and tests using the g_file_storage driver show that PIO is 5 times slower. Perhaps patches have been submitted to fix this.
- The above result is very close to 12Mbps, which is the maximum for full-speed USB. Is this a coincidence, or is something preventing high-speed USB rates ?
I expected the throughput to be much higher...