USB serial console

Ignacio García Pérez iggarpe at gmail.com
Fri Sep 11 05:27:17 EDT 2009


Earlier releases of Dingux had a g_serial console too, but it had some
inconveniences, for example file transfer is possible but a pain in the ass.

So I moved to ethernet gadget. The interface is set as 10.1.0.2/30 and a
DHCP server is configured to provide only one lease which is always
10.1.0.1/30. Inetd is also launched and telnet/ftp services are provided
through it. When the system boots, the PC soon sees a new ethernet card
which is autoconfigured vía the DHCP server. Then you can access the console
vía telnet and transfer files vía FTP.

If you consider this approach, some remarks about the 2.6.24.3 Ingenic
kernel:

1- You must modify the code to enable CDC mode in your code
(drivers/usb/gadget/ether.c).
2- The code needs an small fix so Windows will recognize the ethernet card
(see file above in the dingux kernel source).
3- Something is badly broken either in the Ingenic USB device or DMA code.
The ethernet gadget only works reliably if you disable DMA (put
jz4740_udc.use_dma=0 in the kernel command line). This halves throughput but
works.

I believe the DMA problem is not specific to the ethernet gadget code. I
mean it should be present also when using the g_serial gadget. However, only
shows up when using the full bandwidth, which rarely happens on a serial
console.

Regards.

2009/9/10 Carlos Camargo <cicamargoba at gmail.com>

> HI
>
> I'm working with my custom JZ4725 board, I'm using linux 2.6.24.3 with
> g_serial driver. I can run one console on /dev/ttygserial, so, we don't need
> any USB/serial cable right now.
>
> I can't find the application getty on openwrt, I've already used mgetty,
> but it doesn't work. I try with an openembedded distro, this distro provide
> getty so, I can use it to enable the USB serial console.
>
> Is possible add getty to openwrt?
>
>
> Best Regards
>
> Carlos
>
>
> --
> Carlos Iván Camargo Bareño
> Profesor Asistente
> Departamento de Ingeniería Eléctrica y Electrónica
> Universidad Nacional de Colombia
> cicamargoba at unal.edu.co
>
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