Raspberry Pi Forums

rzusman

trlaing wrote:I agree with Matthew. I use one of my Pis as a media server. It is fine when just playing media from it, but painfully slow at copying media to or from it.

Media write times are going to be the bottleneck.

rzusman

Try typing:
dmesg

rzusman

1) Move the resistor to the Drain side.
2) Put an LED w/dropping resistor on the Gate - this will show when the Gate has voltage.
3) Use anti-static protocol. FETs (even big, beefy ones) can be ruined by static, easily.

rzusman

In case anyone stumbles over this thread: It looks like disabling the boot messages is no issue, since they get echoed to dmesg. As for the getty process - sending a "pause" signal with: # kill -19 $(pgrep -t ttyAMA0) will stop it from using the port until it is resumed with: # kill -18 $(...

rzusman

I don't see why Option 2 would be a problem, as long as you have enough space.
Do you really need a separate power supply for each group of transistors? Why not just get one big enough to handle the whole thing?

rzusman

I don't really understand your question about "bread boards." In my world, a "bread board" is a way of prototyping electronic circuits. If you need a particular interface circuit, it can go at the "far" end or the "near" end, but one location will make more se...

rzusman

A better question is:
"How do you plan on communicating with all these devices?"

Answer that one first.

rzusman

Your setup should work.

I would measure the ground potential difference between the two ends of your system and see if you are outside of the common-mode range of the MAX485.

rzusman

Well, this isn't really a Compute Module - specific topic.
It applies to any Pi device.

I want to be able to start and stop getty from my application, so that I can use the serial port for my own purposes, but have a terminal available if I need it.

rzusman

I need to use both serial ports on the Compute Module. I have read about how to prevent the Console from emitting messages to ttyAMA0 by editing cmdline.txt, and how to prevent getty from using it, too. But - those two features are really, really useful, and I would prefer not to lose them. What I w...

rzusman

http://pcbheaven.com/wikipages/How_Key_Matrices_Works/

rzusman

46 pushbuttons only takes 14 I/O to scan.
That leaves 26 for your joystick and everything else.

rzusman

apt-get install usbmount

Works like a charm.

rzusman

Assuming the drive is mounted at /media/usb, do a
cp /path/to/file /media/usb/directory_to_put_it_in

If the drive is mounted somewhere else, you will need to change the path.

rzusman

There are lots of ways to get it onto the Pi.
The easiest might be to copy it to a USB flash drive and plug it into the Pi, then copy it from there.

Or you could transfer it over WiFi or Ethernet using sshfs.

rzusman

If you are really that worried about heat, pick up some of those cheap stick-on heat-syncs for the ram and NIC controller, then use the case dankcushions suggested and bolt a NH-D15 CPU cooler on it above the cpu, but if that cooler cost too much you can just use a Hyper 212 (plus or EVO) plenty of...

rzusman

I will, but I've had enough experience with customers to know that they are terrible at following directions...

rzusman

Put a TTL-RS232 adapter on it and use the Console.

rzusman

reply to rzusman on unmount scheme As far as my understanding here, Letting device (physical) plug-in and out without (logical) unmount means its logical existence persistently to be used even after plugg-out but if plugged-in again, but that will cause r/w error if an access occurs when currently ...

rzusman

Use an oscilloscope.

rzusman

Thanks for the suggestion, but the usbmount program seems to do exactly what I need.

The next step is to have the CM run a script (actually, one of two or three scripts) when the USB drive is plugged in.

rzusman

usbmount (http://usbmount.alioth.debian.org) does exactly what I needed. Mounts a flash drive at the same location (/media/usb) even if it is removed without unmounting. I believe that you might still be confused about what unmount does--- its more than just correctly returning resources to the sys...

rzusman

usbmount (http://usbmount.alioth.debian.org) does exactly what I needed.
Mounts a flash drive at the same location (/media/usb) even if it is removed without unmounting.

rzusman

OK, so here's what happens: If I have the drive mounted on /mnt/usb, and I unplug it without unmounting it, the next time I plug it in, the device letter gets bumped. In other words, the first time it is /dev/sda1, the next time it is /dev/sdb1, then /sdc1, etc. This is going to be a problem if I ha...

rzusman

I'm working on a Compute Module-based system, which will use a USB Flash drive for software updates. Presumably, users will be too stupid and lazy to wait for the system to unmount the drive before they remove it. I'm not concerned about damage to the file system on the USB Flash drive, but I am wor...

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