Contiki OS

[Nicholas Humfrey]

Hello,

I am not sure if I will have time for this any time soon, but I am very interested in trying to get Contiki OS working on RC2014. While it is billed as 'The Open Source OS for the Internet of Things', it is also just a modern little OS that runs on 8-bit microprocessors. 

It has already been ported to a number of retro machines, including this screenshot of it running on Commodore 64:

https://en.wikipedia.org/wiki/File:Contiki-C64.png

There there used to be support for Z80 and PC-6001 but for some reason it was removed in 2013 - perhaps because it was incomplete/unused.

But to add an Ethernet card, would be amazing :) I imagine that Ethernet chipsets from the Z80 era would be almost as complex as the whole of the rest of the RC2014. How difficult would it be to add a second serial port for SLIP?

nick.

[n.a.m...@gmail.com]

Hello Nick,

Adding another serial port isn't impossible but it isn't trivial either.

The RC2014 SIO board isn't set up to share its interrupt pin so both boards need to be fitted with an open-drain or open-collector driver.
In addition, the address decoder of the second board must be altered to put it at a I/O different address.
The ROM will need to be updated with a new interrupt service routine to work with two SIO boards, if you want to use Basic.

You could do without interrupts on the second SIO board but the OS will then have to poll the second SIO board to see if data has arrived.

Other than that, it'll work fine!

Regards,
Niels.

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[phillip.stevens]

Hi Nick,

 

I am not sure if I will have time for this any time soon, but I am very interested in trying to get Contiki OS working on RC2014. While it is billed as 'The Open Source OS for the Internet of Things', it is also just a modern little OS that runs on 8-bit microprocessors. 

I've also looked at getting an embedded operating system working on the RC2014, but there are a few things needed to make it practical. These include a hardware timer with access to the Z80 interrupt system.

I've worked a lot with freeRTOS, and somewhat with ContikiOS. I find ContikiOS to be quite rich, very complex, and difficult to understand.

Never-the-less, I was able to extract the uIP code from the net to implement it as a freestanding IPv6 solution running on Wiznet W5x00 MACRAW mode.

https://github.com/feilipu/avrfreertos/tree/master/freeRTOS82x/lib-uIP

IMHO, if you don't already know both ContikiOS and Z80 very intimately then it will be a stretch to get it working, if a port doesn't already exist.

My own intention is to build an embedded solution with freeRTOS. So it will be more like embedded solution than a CP/M system.

There are already many Z80 resources available for freeRTOS, so it will be not too much of a stretch... I hope.

http://www.freertos.org/portez80.html

https://github.com/notwendig/FreeRTOS-eZ80F91

But to add an Ethernet card, would be amazing :) I imagine that Ethernet chip-sets from the Z80 era would be almost as complex as the whole of the rest of the RC2014. How difficult would it be to add a second serial port for SLIP?

Initially, had a plan of adding a Wiznet W5300 device to my board. But, the chip is a 100 pin device, using 3.3V. So, it was a bit complex to add this to my first Z80 board design. It's been added to the "To-Do Later List".

https://feilipu.me/2016/05/23/another-z80-project/

The Wiznet W5x00 series is a great way to get IP on a modern or ancient 8-bit device. They have a substantial Tx/Rx buffer which can support processing in place. On an AVR with 1kB of RAM (which is less than a single Ethernet frame, for example) having this buffer and the whole IP stack in hardware makes things easy (i.e. possible).

https://github.com/feilipu/avrfreertos/tree/master/freeRTOS82x/lib_iinchip

To add SLIP, I'm pretty sure you'd need to have access to the Z80 interrupt system, and possibly have a Rx buffer on your USART,

Cheers, Phillip

[Scott Lawrence]

I added another serial port to mine (At $C0) although it doesn't share the interrupt just yet.  I need to extend it as said above to check both ports.  It does work well though.  It required the same parts as the "main" serial port, plus one extra chip to decode the address.

-s

On Sun, Aug 7, 2016 at 4:56 PM, <n.a.m...@gmail.com> wrote:

Hello Nick,

Adding another serial port isn't impossible but it isn't trivial either.

The RC2014 SIO board isn't set up to share its interrupt pin so both boards need to be fitted with an open-drain or open-collector driver.
In addition, the address decoder of the second board must be altered to put it at a I/O different address.
The ROM will need to be updated with a new interrupt service routine to work with two SIO boards, if you want to use Basic.

You could do without interrupts on the second SIO board but the OS will then have to poll the second SIO board to see if data has arrived.

Other than that, it'll work fine!

Regards,
Niels.

Hello,

I am not sure if I will have time for this any time soon, but I am very interested in trying to get Contiki OS working on RC2014. While it is billed as 'The Open Source OS for the Internet of Things', it is also just a modern little OS that runs on 8-bit microprocessors. 

It has already been ported to a number of retro machines, including this screenshot of it running on Commodore 64:

https://en.wikipedia.org/wiki/File:Contiki-C64.png

There there used to be support for Z80 and PC-6001 but for some reason it was removed in 2013 - perhaps because it was incomplete/unused.

But to add an Ethernet card, would be amazing :) I imagine that Ethernet chipsets from the Z80 era would be almost as complex as the whole of the rest of the RC2014. How difficult would it be to add a second serial port for SLIP?

nick.

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[Nicholas Humfrey]

> I've also looked at getting an embedded operating system working on
> the RC2014, but there are a few things needed to make it practical.
> These include a hardware timer with access to the Z80 interrupt
> system.

Presumably that would be a useful thing to exist anyway?
Could it be done with a new Clock board? Or would it need additional bus
lines?

> I've worked a lot with freeRTOS, and somewhat with ContikiOS. I find
> ContikiOS to be quite rich, very complex, and difficult to understand.
> Never-the-less, I was able to extract the uIP code from the net to
> implement it as a freestanding IPv6 solution running on Wiznet W5x00
> MACRAW mode.
> https://github.com/feilipu/avrfreertos/tree/master/freeRTOS82x/lib-uIP

Cool! I don't know a lot about freeRTOS, I should find out some more.

I am not sure how I didn't know about the MACRAW mode of the Wiznet
chips.
Going a bit off-topic but I have been working on an IPv6 library for
Arduino:
https://github.com/njh/ethersia

I will have to try getting it to work with Wiznet. A bit crazy writing
an IPv6 stack but I found that even Contiki/uIP was using up a lot of my
programme/RAM space (on Arduino). Plus it is a hobby not work :)

> IMHO, if you don't already know both ContikiOS and Z80 very intimately
> then it will be a stretch to get it working, if a port doesn't already
> exist.

Yes, I totally agree. I don't think it would be 'quick win'!

> Initially, had a plan of adding a Wiznet W5300 device to my board.
> But, the chip is a 100 pin device, using 3.3V. So, it was a bit
> complex to add this to my first Z80 board design. It's been added to
> the "To-Do Later List".
> https://feilipu.me/2016/05/23/another-z80-project/

Your project looks awesome :)
Impressive that you got as far as making such a complex PCB.

> The Wiznet W5x00 series is a great way to get IP on a modern or
> ancient 8-bit device. They have a substantial Tx/Rx buffer which can
> support processing in place. On an AVR with 1kB of RAM (which is less
> than a single Ethernet frame, for example) having this buffer and the
> whole IP stack in hardware makes things easy (i.e. possible).
> https://github.com/feilipu/avrfreertos/tree/master/freeRTOS82x/lib_iinchip

I have been using ENC28J60 in a number of projects. It has the advantage
of having a low pin count, 5v tolerant and even comes in a through-hole
package. While you have to implement Ethernet/IP/TCP on the main CPU it
is just about possible to do some useful things without using up all
your RAM/ROM on an ATMEGA328. And RC2014 has a lot (!) more RAM/ROM than
an AVR.

But doing SPI on a Z80 seems a bit weird, with all the address and data
lines available?

> To add SLIP, I'm pretty sure you'd need to have access to the Z80
> interrupt system, and possibly have a Rx buffer on your USART,

Yeah, probably not going to be easy on current hardware.


nick.

[phillip.stevens]

> I've worked a lot with freeRTOS, and somewhat with ContikiOS. I find
> ContikiOS to be quite rich, very complex, and difficult to understand.
> Never-the-less, I was able to extract the uIP code from the net to
> implement it as a freestanding IPv6 solution running on Wiznet W5x00
> MACRAW mode.
> https://github.com/feilipu/avrfreertos/tree/master/freeRTOS82x/lib-uIP

Cool! I don't know a lot about freeRTOS, I should find out some more.

For someone who just doesn't get C++ (me), freeRTOS is a very good thing.

It is really just 3 .c files (tasks.c, queues.c, and lists.c) everything else is built on top of it.

The port layer is just configuring a hardware timer to trigger the scheduler, the register swap out and in, and macros enabling and disabling interrupts.

I am not sure how I didn't know about the MACRAW mode of the Wiznet
chips.

The Wiznet chips (W5100, W5200, W5300, and W5500) can all peel away their hardware support, to enable just a pure MAC layer.

You can use this to emulate simpler devices, or to build your own IP layer (such as uIP or lwIP) on top.

I will have to try getting it to work with Wiznet. A bit crazy writing
an IPv6 stack but I found that even Contiki/uIP was using up a lot of my
programme/RAM space (on Arduino). Plus it is a hobby not work :)

I feel your pain...

RAM limitations on Arduino Uno caused me to build the original Goldilocks board, and then this:

https://www.tindie.com/products/feilipu/goldilocks-analogue/

 

> https://feilipu.me/2016/05/23/another-z80-project/

Your project looks awesome :)
Impressive that you got as far as making such a complex PCB.

Thanks. ;-)

Progress is held up awaiting hacking a new SMD oven I just bought,

because my SMD capable friend just got a job at Espressif,

and has no time to help any more ;-(.

But the upside is I get to learn how to solder SMD... ;-)

 

> The Wiznet W5x00 series is a great way to get IP on a modern or
> ancient 8-bit device. They have a substantial Tx/Rx buffer which can
> support processing in place. 

But doing SPI on a Z80 seems a bit weird, with all the address and data
lines available?

The W5300, which had I meant to say that I was going to use, doesn't use SPI.

It uses either 16bit or 8bit parallel data, together with 10 address lines in direct addressing mode.

Hence, it is perfect to integrate with the Z80.

Which is great, except the W5300 chip requires 3.3V to operate (but has 5V tolerant inputs), and that means yet another power supply on the board.

And, with 100 pins of SMD, it was just too complex for a first build.

Maybe, next time.

Cheers, Phillip

[Tobias Mädel]

Contiki needs quite a lot of RAM and the bank switching gets ugly quite
quickly.

Other than that: adding another serial is easy, you'd have to change the
address decoding logic a bit. Unfortunatly the ACIA is fixed at 115200
baud in this configuration.

So long,
Tobias
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