Ashtead's Journal: Summertime II

Ten days ago I put in an order for some Picotux units. Last Tuesday, just as I had arrived at my sister's place in Nøtterøy, I got a phone call from UPS, that they had tried to deliver a package with some electronic components from Germany at my house and I wasn't there. What to do? I made an agreement that I'd come pick it up at their customer service center in Økern, Oslo, on Wednesday or Thursday.

Meanwhile I'd be installing network cables at her house. They have just had their DSL and VoIP units cluttering the living room, so there was a lot of rejoicing when I had moved them to the basement, near the point where the telephone cable enters, and just run a CAT5 up to a closet in a room off the living room, and put a wireless router there. Yes, my opinions on wireless are still not the best, but I'd thought I'd at least make a decent attempt at making it work there. As it turned out, the wireless parts did work fine, but there is a cable connection available there just in case. War-walking around their lot confirmed that the signals were good enough.

I have got a nice tan by now, sitting out in the sun. Weather has been really nice for vacation purposes this summer; as of writing this at 8.15 PM, there is 26 degrees C outside ... tonight could yet be a "tropical night" which is what we call it when the temperature stays above 20 C all night.

After the networking stuff was put in order, I went and picked up the picotuxes, 6 in all, of which one came as part of the "starter kit". So far, I have powered up that one, the one that has been mounted on a circuit board, and noticed a few things:

1. There is a serial connector that supports a terminal at 38400 Baud, no parity, 8 data, 1 stop, and the unit has a shell running here using this as the console. A second shell can be had by telnet-ing into the network port, it is just that one will have to figure out what the IP-address is first. /sbin/ifconfig in the serial port shell, or inspection of the DHCP table in the router will reveal this. Also, since this is DHCP, it seems to give different IP-addresses every time it is powered on.

2. The default configuration has a read-only root filesystem, so no editing the /etc files to change the DHCP into a fixed address, or adding other interesting actions during start-up. I will have to figure out the way the flashing works using DHCP, BOOTP, and TFTP... so I can change this. For testing however, there is a /usr filesystem which is read/writeable, and the unit also can work as an NFS client, so there is an easy way of accessing test programs and copying these program files into the memory of the unit.

3. I guess the limitation is that the root file system must be present before the drivers for the flash, read/write system are present, but the changes really only have to be to some of the files in /etc, so I might be able to edit the file-system and re-load it, then put my programs into /usr to be auto-run at the end of initialisation. I may also want to use the serial port for some interfacing to other hardware, so I will have to disable its shell, and just use the one available through telnet. There is a date command in the shell, but the circuit does not contain a live clock so it starts off at 1/1/1970 on each powerup, so some kind of clock-setting action on startup will likely be required.

4. Then there is the matter of getting the cross-compiler set up right. True to form, there is a CD with the entire source for everything on it, and there are binaries for i386 hosts, but there is somewhat thin documentation, apart from Makefiles and examples and source ... so I'll have to get some kind of "Hello World" going first.

5. The 5 digital lines have been assigned to the five serial-control lines on the unit with the circuit board, so there are 3 inputs and 2 outputs. Unless I were to attempt desoldering of tiny surface-mount resistors, I'd have to stick to this IO-assignment.

6. The other 5 units are loose ones, without any supporting circuits at all, and I will have to make a 3.3V supply for them, and also figure out a good way to connect things to the 1.27 mm pitch connector on it. I don't know if these also have the same basic installation of Linux and Busybox, and I will have to have a 3.3V supply going before I can find this out. Hopefully this is the same there, so I can begin by telnetting in through the network. I'll also try connecting some switches and LEDs to the 5 GPIO lines here, and see how well I can control these. Then it will be on to connecting some latches or shift registers, so I can read and control things with many more bits. There also appears to be an I2C interface there of some kind, which might be useful for something.

I'll be keeping notes!

Nice!

[Arker]

Question? Where are you getting your DHCP from? If you want a static IP you should be able to just have the DHCP server always give that Mac the same IP address. Assuming it's under your control... I use a cheap router to do that.

Be very very careful turning off the serial console ;) could make it a brick if you screw up the network afterwards. Hopefully there's some sort of hardware reset that will set it back to factory-defaults?

Re:Nice!

[Ashtead]

I get the DHCP from a router (an SMC Barricade) right now. So I could do as suggested, make it assign the same IP address for the MAC each time. It doesn't look like the router has this feature in its menu, but I will have to change this anyways when I will be trying to download a new kernel to the picotux unit; then I will have to run a dhcpd on one of the Linux machines here instead.

The picotux doesn't remember its IP-address from time to time, so it cannot just ask the router for it to be reassigned;

That's so cool!

[October_30th]

I've always wanted to build and experiment with a cluster of linux machines, but I don't have a suitable room for a ten or so boxes (mainly noise constraints). Picotux looks interesting.

Re:That's so cool!

[Ashtead]

I guess one can just connect any number of these onto a network, and have them talk to each other and do something interesting. From what I have seen so far they appear quite capable when it comes to networking, similar to any other machine running a 2.4 series Linux kernel.

They do not have any development tools actually present in the units themselves, not even a text editor ... so in order to make programs for them, you will need to have one regular PC, preferrably with Linux on it, to run the cross-com