Alpha Clock 5 serial question

jj33

I bought my clock to hack on but got frustrated with it a have just been using it as a straight-up clock (which it's very good at).  Tonight I got an itch to play with it again and decided that an easy entry point would be to try to communicate with it over serial.  I'm now almost positive this is where I got frustrated last time.

When plugging in the TTL-232R cable from either a Mac or Linux machine, I don't get a device in /dev to attach to to communicate with the clock.  I don't have a windows machine at the moment but I did the last time I tried and I had the same experience there.

It occurred to me that I should probably rule out a bum cable since I've never used this cable for anything else.  I used the came cable between the Mac and a raspberry pi and I was able to log in to the pi over the serial console.  That's not apples-to-apples since you don't use all 6 pins of the cable in that arrangement, but at least I knew the cable wasn't at a total loss, and confirmed that my Mac _could_ use the cable.

After some more poking around I realized the power pin for J2 is labeled 5V, and that on the wiki page for serial communication with the clock you specifically link to the 5v version of the TTL-232R cable.  As it happens I bought the cable I'm attempting to use from adafruit and it is the 3v3 version.  I'm very willing to buy a new cable, but I don't want to buy it if this 3v3 cable _should_ work.  Do the communication problems I'm having seem likely to be caused by using the 3v3 cable instead of the 5v cable?

Not sure it matters but I assume my clock has the v1 firmware on it since.  I haven't touched it in a year or so and it's running whatever shipped on it.

Thanks for your help!

Windell Oskay

Hi jj33,
The FTDI cable (either in the 3.3 V or 5 V version) *should* work just fine on all three platforms, both for programming and serial communication. 

 On the mac, you should indeed see it show up under /dev, as both /dev/cu.usbserial-xxxxxxxx and /dev/tty.usbserial-xxxxxxxx. 

  It should also show up in Arduino, in the Tools>Serial Port menu. If it is not there, you may need to install or update the FTDI "VCP" drivers in order for it to show up correctly, and to use it for communicating with the Alpha Clock Five. 

 Two other things: Consider updating to firmware v2 as soon as possible; it's much easier to work with. And, please feel free to ask questions here in the forums, hopefully before you get frustrated next time.

jj33

Thanks for your response Windell.  I would definitely like to upgrade the firmware, getting this cable to work with the clock is a step on that path hopefully.

Thanks for confirming the 3v3 version should work, now I can concentrate on debugging instead of buying more stuff.

(time passes)

And now I can confirm that I got it working.  I have found out that if I plug the cable into the clock first, then into a computer, I never get a device.  This is reliably reproducible.  It's also what I was doing over and over last night because it's much easier to plug/unplug the USB end than the clock end.  However, if I plug into a computer first, then plug into the clock, I get the device and can at least attach to it (which is as far as I'll get in working on it this morning).

Further confusing things, I can definitely speak serial with the pi when I connect the pi first, then to a computer.  Again, I know that this isn't apples-to-apples with the clock connection, but it is still odd.

So, I can get a device to speak with the clock, and I can play with it more tonight.  yay!

Do you have any insight into the issue I'm having with order of cable connection being important?  I've never seen that written down anywhere, not sure if it's part of the unwritten lore of that cable, or the clock, or something specific to my clock/cable (doubt it's the computers or OS since I've confirmed the behavior with 2 of each).  Not sure it matters any more but I am very curious about it.

Thanks again for taking the time to respond and giving me hope to keep poking at the problem!

--John

Windell Oskay

I'm afraid that yes, this falls under "unwritten lore" of that cable.  If it doesn't work, unplug one end, then the other.   There must be something about the way the chip keeps itself safe that causes this behavior.  For me, if it doesn't mount, I unplug the computer end, and then it works. :P 

Good luck with the more interesting challenges!