[GreenKeys] USB-teletype adapters (update)

Tue Mar 29 05:26:35 EDT 2016

On 03/28/2016 7:16 pm, Gil Smith wrote: 

> Hey Eric: 
> 
> I also use Eagle (for ten years now). Quirky, but I am quite used to it now, and can do anything I need. I build all my part footprints/symbols/devices as anything online is goofed-up somehow. 
> 
> I also have used myropcb for years and like them a lot. Their "standard" pcb pricing is awesome and the cheapest per-square-inch deal I have found (unless you try to pack more than one board into a design and they want to add $50 per, in which case just make the bottom ground plane cover the entire array so they don't notice, and the cut them apart on your bandsaw). I frequently pack several rather-large boards together, get 40 or so made, and it costs me about $100. Pretty good deal. 
> 
> The only drill issue I have run into is size, as they use 0.5mm drill increments. So my smallest via hole of 0.015" (with a 0.025" pad and 0.005 annular ring) gets morphed into either a 0.35mm (0.0138"), or they bump it to a 0.40mm (0.0158') hole and them inflate my pads a bit to the point of possible solder whiskers. I need to just standardize my via holes to 0.35mm I guess. 
> 
> I have not done assembly at seeed, though I have perused their open-parts-library and found much of what I can use. I presume you can send special parts on consignment for a build, but have not looked into it. 
> 
> Like you, I would want all my smt assembly done so the only thing left to solder is a few through-hole headers 'n such. Even though I am getting quite good at hand-soldering 0402 passives, and IC and connector pitches down to 0.5mm (0.0197") with a simple solder-blob and solder-wick technique, I too want to minimize such soldering experiences. 
> 
> Also, myro does assembly, but the info on their site is so ill-defined and goofy that I have never tried their assembly. 
> 
> I have never, and hope to never, do anything with a BGA. If I can't hand-solder the prototype (even with an oven or fry pan), I can't do any proper rework either. And I don't have an x-ray machine to inspect the inner balls. If I can't see my balls, well, it is a real problem. 
> 
> gil 
> 
> gil smith, AF7EZ
> greenkeys moderator
> gil at baudot.net

Well, we'll see how Myro do on assembly soon, they are building all the
usb-tty adapters. :) They were actually quite easy to communicate with
about it and even caught a small mistake in my BOM that I hadn't
noticed. I too have had to "trick" them when panelizing but I hardly
ever do anything that elaborate. I stopped using their website and just
email sales@ - it's one guy and if you ask for something he just makes a
quote for you and you don't have to navigate the janky quote system on
their site. 

I have no idea whether Seeed will let you consign parts that they don't
stock themselves, because I've asked them three times now that very
thing and they've never responded. I've given up. Also, they recently
cut their OPL library down by a factor of three, so there's much less to
pick from now, for instance they dropped all the STM32 mcu's, and many
of the AVRs they had. 

When I asked Myro about consignment they responded in like an hour and
said it wasn't necessary to ship, I could just send them the BOM from
digikey and they'd order directly. I agree with you on soldering. I
don't mind doing it for prototypes but it's not that fun. I end up
designing with QFNs a lot and they kind of suck to hand solder or rework
too. I wouldn't do it in a production scenario. BGA too - I'd probably
try small 2x3 or whatever ones but not anything big. 

eric 

> -------- Original Message --------
> Subject: RE: [GreenKeys] USB-teletype adapters (update)
> From: Eric <epvgk at limpoc.com>
> Date: Sun, March 27, 2016 12:50 am
> To: Gil Smith <gil at baudot.net>
> Cc: aaa-greenkeys <greenkeys at mailman.qth.net>
> 
> On 03/26/2016 11:15 pm, Gil Smith wrote: 
> Sheesh, been a while on 33 data format. Maybe Wayne or Jack or Jim or somebody will add something. I seem to recall it was 8 bits (7 ascii plus mark in top bit maybe?), no extra parity bit, and needed two stops for the mechanics. Something like that. 
> What pcb layout prog did you use? What fab/assy place? Tiny stuff. Nicely done. 
> gil 
> Well, I guess at some point I'll get someone to try one of these on a 33 and see if it works. The bitbanged serial uart isn't too complicated so it can probably be made compatible. 
> Thanks, the design was done with Eagle, and the board fab and assembly are being done by Myro in China. I quoted it with a bunch of companies and these guys win in terms of price and being fairly easy to deal with, for instance I was able to just supply them a Digikey parts list. They also did most of the rtty demod boards last time around. My only complaint with them is that they're a little sloppy with drill placement, but it's fine if you plan for it. I dunno if I'd try BGA stuff with micro-vias though. 
> I had the prototype boards assembled by Seeedstudio.com [1], who have great prices and are very fast, but are not as easy to deal with and will only do assembly with parts they supply/stock, which is annoying because a half-populated board isn't that useful in bulk. (I hand soldered the other half of the parts on those, but I'm not doing that for 80 units!) 
> gil smith, AF7EZ
> greenkeys moderator
> gil at baudot.net 
> 
> -------- Original Message --------
> Subject: RE: [GreenKeys] USB-teletype adapters (update)
> From: Eric <epvgk at limpoc.com>
> Date: Sat, March 26, 2016 9:18 pm
> To: Gil Smith <gil at baudot.net>
> 
> On 03/26/2016 8:56 pm, Gil Smith wrote: 
> Nice job on that board Eric. 
> Regarding the 33, in addition to it being 110 baud, be sure to put 2 stop bits in. 
> gil 
> Ah thanks, I was hoping someone would chime in. Do you know if they want or require parity bits, or whether they need delays inserted for carriage return? 
> eric 
> gil smith, AF7EZ
> greenkeys moderator
> gil at baudot.net 
> 
> -------- Original Message --------
> Subject: [GreenKeys] USB-teletype adapters (update)
> From: epvgk at limpoc.com
> Date: Sat, March 26, 2016 1:51 pm
> To: greenkeys at mailman.qth.net
> 
> Hi Folks, 
> 
> Just an update. Manufacturing is in progress, they're supposed to be done
> April 20th. I'm building enough for everyone who's asked so far plus some
> extras. I don't want to take anybody's money until the boards are in my 
> hands and I know there are no problems. 
> 
> Software updates:
> 
> selectable/modifiable translation tables: you can have up to 6 separate
> tables and switch between them. You can create or overwrite tables
> by entering them in hex at the config command line. 
> 
> bidirectional break handling: detects break in the loop, and can break the
> loop if it gets a break signal from the host. 
> 
> ASCII mode: seems to work, but I have no 33 to test with. Particularly I don't 
> know how real machines handle/require parity, etc. 
> 
> eric
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