Some quick Pi2 questions

Hi,

Just got home. Pi2 has arrived. :-) I’ll need to get an RTC for it, I guess.

Anyway, some quick questions (it’s multiple choice!) if anybody has the time/inclination:

• I’m guessing the headphone jack is now a four-pole, with the video at the far tip?

• Given its a quad core processor with four USB ports, is it possible to pump some useful current into this thing, or will its power regulation wimp out? For the life of me, I dunno why they just don’t stick a barrel connector on it and be done. Or, at least, one of the chunkier USB sockets.

• What is the unused J5 on the bottom? Looks like only a few tracks to the larger number of pins – some sort of serial port for GPU debugging? Or JTAG?

• Whoo. We can see the Broadcom chip this time. I’ll have to see if it runs hot. Got myself a heatsink (dinky little thing) to fit if necessary. If not, I’ll open up the Vonets and fit the heatsink to that.

• While it is nice to have four USB ports (no faffing around with hubs and stuff), there’s still only the ONE controller in the SoC right? So that SMSC chip is pretty much a hub with USB Ethernet thrown in. I think it is funny that people are asking for USB3 in a Pi when we don’t have independent USB2 channels yet. :-)

• What the heck is up with the tracks to the south of the SoC? The connections to the HDMI are wibbly like a girl’s hair crimper, and the ones to the camera port are both that and a diagram of a mountain road. I’m guessing there is an explanation – but what?
  Having seen some of the weirdo stuff that passes for a WiFi antenna, I’m guessing it might be something to do with reducing signal interference, though I don’t get how making it wibbly can do anything. Capacitance is strange…

• Will hardware that works on a Pi1 work on the Pi2, or are there changes to the GPIO that it ought to be aware of (bigger isn’t a problem, 5V where GND used to be is).

• Any code for playing with other cores under RISC OS? I saw it discussed here, but not sure if anything was ever released. I’m not expecting to run applications, just to get something running on another core just, pretty much, for the sake of it.

Sorry, I have to be up real early tomorrow (the run up to Christmas is busy period at work) so I’m turning in now…

Any code for playing with other cores under RISC OS? I saw it discussed here, but not sure if anything was ever released. I’m not expecting to run applications, just to get something running on another core just, pretty much, for the sake of it.

There’s some very bare-bones test code here, but that’s about it so far. I do have some code which enables the MMU (sharing RISC OS’s page tables) and sets up some basic processor vectors, but it’s dependent on some HAL changes that haven’t gone through yet, and sharing the memory map with the OS is a bit dangerous because our memory management isn’t SMP-friendly yet.

Capacitance is strange…

With the rise and fall times that we’ve been used to these last 20 years or more, the inductance of tracks is just as important as the capacitance. Look up “transmission lines”.

I happened to be interested in the maths of transmission lines at university, and there have been countless times in my career when I’ve been glad I learned about them and understood.

Yes/no. It is a four pole, with ground at tip, video next.

I found a pinout and…
http://www.raspberrypi-spy.co.uk/2014/07/raspberry-pi-model-b-3-5mm-audiovideo-jack/
…it sort of implies that shoving a regular headphone jack into the socket might not work? Hmm.

And yes still one USB channel, just like a PC.

According to the system information of my PC, there are two independent USB controllers. One goes to a hub for the ports on the back, the other goes to a hub for the two ports on the front and some internal stuff. Transferring files from harddisc to harddisc is faster if I connect one to a front port and one to a back port…

…it sort of implies that shoving a regular headphone jack into the socket might not work? Hmm.

No, standard headphone/speaker plugs will work, they are Tip left, ring right and sleeve earth (as all Pi’s since B+).