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[TUTORIALS] Lesson 10: Ethernet

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Till Harbaum
2016-01-14 11:39:57 +01:00
parent 29d9c7124b
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@@ -554,12 +554,13 @@ Files required on SD card:
![Lesson 10: Ethernet](lesson10/lesson10.png)
Only few computers of the homecomputer era came with some kind of network interface included. But for many
there were add-ons like the [C64](http://dunkels.com/adam/tfe/), the
[Atari ST](http://hardware.atari.org/ether/) and some Amigas could use PCMCIA ethernet cards.
Only few devices of the homecomputer era came with some kind of network interface included. But for many
existed add-ons like the [TFE for the C64](http://dunkels.com/adam/tfe/), the
[Etherncx for the Atari ST](http://hardware.atari.org/ether/) and some Amigas could use PCMCIA ethernet cards.
The MiST can use certain USB to ethernet interfaces based on the Asix
chip to connect to an ethernet. One such adapter is the [D-Link
The MiST is able use certain USB-to-ethernet adaptors based on certain
[Asix chips](http://www.asix.com.tw/products.php?op=pItemdetail&PItemID=86;71;101&PLine=71)
to connect to an ethernet. One such adapter is the [D-Link
DUB-E100](http://www.dlink.com/de/de/support/product/dub-e100-high-speed-usb-2-fast-ethernet-adapter). Similar
to the mouse and the keyboard the IO controller again hides all the
USB complexity from the core. The core just needs to implement a
@@ -568,44 +569,45 @@ network packets. The IO controllers firmware will care for the rest.
The conection to the IO controller is again handled inside
[`user_io.v`](https://github.com/mist-devel/mist-board/tree/master/tutorials/soc/lesson10/core/user_io.v). Since
only few cores implement ethernet most `user_io.v` files don't
implement this. So you have to make sure to start with a `user_io.v`
including ethernet features if you intend to implement
ethernet. `user_io.v` only deals with the communication with the IO
controller and e.g. doesn't buffer any packets. This has to be
implemented depending on the demands of each core. For this tutorial
the Z80 just needed a simple network interface. This has been
implemented in
only few cores make used of ethernet most `user_io.v` files don't
include the necessary parts. You have to make sure to start with a
`user_io.v` including ethernet features if you intend to implement a
network interface. `user_io.v` provides an ethernet related
communication channel to the IO controller. But it e.g. doesn't buffer
any packets. This has to be implemented depending on the demands of
the core. For this tutorial the Z80 just needed a simple custom
network interface which has been implemented in
[`eth.v`](https://github.com/mist-devel/mist-board/tree/master/tutorials/soc/lesson10/core/eth.v).
The files `eth.v` interfaces between the Z80 CPU and the connections
to the IO controller provided by `user_io.v`. Send and receive buffers
The file `eth.v` interfaces between the Z80 CPU and the connection to
the IO controller provided by `user_io.v`. Send and receive buffers
inside `eth.v` make sure that ethernet packets can easily be exchanged
between the IO controller and the SoCs Z80 CPU. If you intend ethernet
for an retro machine you might want to implement `eth.v` in a way that
it is compatible to one of the original interfaces so that the
original driver software can be used. E.g. the Atari ST core
implements an [ethernec compatible
interface](http://hardware.atari.org/ether/) this way and thus doesn't
need any drivers to be newly written.
without data loss between the IO controller and the SoCs Z80 CPU. If
you intend to implement ethernet for a retro machine you might want to
implement `eth.v` in a way that it resembles one of the original
interfaces so that the original driver software can be used. E.g. the
Atari ST core implements an [ethernec compatible
interface](http://hardware.atari.org/ether/) and thus doesn't need any
new drivers but used the original drivers written for the ethernec.
Since there's no existing software for our little Z80 SoC we have to
implement it our own network stack and drivers. For full network
Since there is no existing software for our little Z80 SoC we have to
implement our own network stack and drivers. For full network
connectivity this requires a full blown TCP/IP stack. Such kind of
software is rather complex and is close to the limits what a small
homecomputer of the 80ies can handle. For this totorial we selected
software is rather complex and is close to the limits of what a small
homecomputer of the 80ies can handle. For this totorial we choose
[Adam Dunkels UIP stack](https://github.com/adamdunkels/uip) to
provide the necessary network stack. It turned out that this stack has
some issues with the SDCC compiler we are using. I ironed out the most
critical problems until i had it working as a web server. When running
the
critical problems until i had it somewhat working as a web
server. When running the
[`z80_soc.rom`](https://github.com/mist-devel/mist-board/raw/master/tutorials/soc/lesson10/boot_rom/z80_soc.rom)
you'll be presented with the MAC address of your Ethernet USB dongle
and the hard coded IP addresses on a VGA screen connected to the MIST.
If you the message `Wait for ETH` doesn't disappear then the MIST
doesn't recognize your USB ethernet dongle or you don't have one
connected at all. Once you see the IP confuguration being displayed
you can ping the MIST under IP `192.168.0.2` from a PC or you can
access the embedded webserver from a PC under `http://192.168.0.2`.
you'll be presented with the MAC address of your Ethernet USB adapter
and the preset IP addresses are displayed on a VGA screen connected to
the MIST. If the message `Wait for ETH` doesn't disappear then the
MIST doesn't recognize your USB ethernet dongle or you don't have one
connected at all. Once you see the IP configuration being displayed
you should be able to `ping` the MIST under IP `192.168.0.2` from a PC
and you should be able to access UIPs embedded webserver from a PC
under `http://192.168.0.2`.
Please be aware that the whole setup is not a high performance network
device and the transmission is neither fast nor very reliable. Also
@@ -616,17 +618,16 @@ the limited performance of an 8 bit Z80 system. With a total of
30kBytes code this very basic network setup is already close to the
32kBytes code limit of our small SoC.
To reduce the load on the core a little bit the IO controller does
some network filtering. It will only forward packets to the core which
are directly addressed to its MAC address and which are ARP
broadcasts. All other (broadcast/multicast) traffic is not forwarded
to the core to reduce the load on the core a little bit and to protect
it from all those modern protocols causing lots of background noise in
a typcial home network of today. This may affect fancy auto conf
network setups trying to run on the MIST. If you encounter problems
with this filtering, then please get in touch with us and we will find
a way to solve the problem. But ordinary IP traffic is supposed to
work.
To reduce the load on the target system a little bit the IO controller
does some network filtering. It will only forward packets which are
directly addressed to its MAC address or which are ARP broadcasts. All
other (broadcast/multicast) traffic is not forwarded to the core to
reduce the load a little bit and to protect it from all
those modern protocols causing lots of background noise in a typcial
home network of today. This may affect fancy auto conf network setups
trying to run on the MIST. If you encounter problems with this
filtering, then please get in touch with us and we will find a way to
solve the problem. But ordinary IP traffic is supposed to work.
Links:
- [UIP 1.0 on github](https://github.com/adamdunkels/uip)