Sideport SAMS?

[+jedimatt42]

25 minutes ago, OLD CS1 said:

And polarity.  Don't forget polarity!

 

I have a ZX Spectrum reproduction, that intelligently uses a bridge rectifier chip ( tiny little thing ) to make polarity not matter... 

 

-M@

[wierd_w]

While nobody uses the things, I would be fine with USB-B connector.  (like found on old printers.)

https://www.newark.com/molex/67068-8011/usb-conn-2-0-usb-type-b-rcpt-tht/dp/49Y4726?gclid=Cj0KCQiAn8nuBRCzARIsAJcdIfMsntORFIG45__Zln6Axg-t5QXbgRRkoLaq82V7lZ2zNmMWtpa-RA4aAkHAEALw_wcB&mckv=s05lAeh4W_dc|pcrid|81515568741|plid||kword||match||slid||product|49Y4726|pgrid|20376566901|ptaid|pla-842094498124|&CMP=KNC-GUSA-GEN-SHOPPING-Connectors

 

My beef with USB as a power plug, is that everyone wants to leverage shitty cellphone chargers (which use micro USB B, because of space constraints), while paying no service at all to the rigidity or longevity of the port.

 

USB-B is very sturdy. Possibly more sturdy than DC Barrel. (just more expensive.)  It's keyed, so you can't put the lead in wrong, and you don't have to worry about it being wired wrong internally or supplying incorrect voltage.

[PeteE]

1 hour ago, wierd_w said:

My beef with USB as a power plug, is that everyone wants to leverage shitty cellphone chargers (which use micro USB B, because of space constraints), while paying no service at all to the rigidity or longevity of the port.

Standard USB has a minimum rated lifetime of 1,500 cycles of insertion and removal, the mini-USB receptacle increases this to 5,000 cycles, and the newer Micro-USB and USB-C receptacles are both designed for a minimum rated lifetime of 10,000 cycles of insertion and removal. To accomplish this, a locking device was added and the leaf-spring was moved from the jack to the plug, so that the most-stressed part is on the cable side of the connection. This change was made so that the connector on the less expensive cable would bear the most wear.

[wierd_w]

I dont want to argue, but personal experience is that the port's tiny size and lack of a rubust shell downhanger thru-hole for the grounded shell, means that yaw-forces over time weaken the port. The contacts inside can handle the insertions, but the port's solder points get stresses on them that they shouldn't, because of the design. (Designed for low profile, in restricted area. Almost exclusively SMT in design.)

 

I would much prefer something that I can gently retouch with a hot iron to reflow when it starts to walk out of its proper spot. DC barrel, and USB-B let me do that.

[+FarmerPotato]

23 hours ago, jedimatt42 said:

Enough people have failed to plug the correct sort of power into the sideport 32k, that I'd recommend a safety over cost solution.

 

I don't know if that is also possible with a 5v source.  5v is very convenient.

 

People tend to think a barrel jack fitting has some significance. Sadly it doesn't work that way in practice.

 

-M@

So SparkFun have a short introduction to their favored barrel jack, the PJ-202A, which also happens to be in the KiCad library. They say they use 2.1mm jack tip, 5.5mm jack sleeve, since it's the most common. The datasheet they link to  shows  2mm tip and  6.5mm outer diameter of the barrel jack. I confirmed this at Mouser, 6.5mm (where 50 cost $0.45 each).

 

Is this the infamous "loose" barrel connection? I cut it out of paper (10x) and (6.5-5.5)=1mm space / 9mm depth seems awfully wiggly. I measured the real thing, and it is terribly wiggly despite the spring contact inside.

 

Then I figured out that my wiggly plug takes a 2.5mm pin, and that it's the 7.5V DC adapter donated by Charles Good with a CF7+ (that needs a new barrel jack anyway). The other two I have on my desk are 5V, take 2.1mm pins, and mate snugly with the CJ-202A.

 

This jack costs  0.80 at Mouser but lists outer diameter 5.5mm, tip 2.1mm. Maybe it is too tight? 

 

Anyhow, I now know that I can eliminate that pesky 2.5mm plug I have, and feel good about using the cheap jack.
 

[wierd_w]

I personally like the 3 legged ones for the stability they give.  I can't really tell if that one is 3 legged or not with the orientation of the pic.

[+FarmerPotato]

6 hours ago, wierd_w said:

USB-B is very sturdy. Possibly more sturdy than DC Barrel. (just more expensive.) 

 

So I looked at USB parts

 

.

 

I found USB micro B jacks with no thru-hole pins at all (not even shield). The one in KiCad looks like it has anchor pins. It's Wurth Elektronik 629105150521 and it costs $1.76 (@Qty 50) at Mouser. (random other 3D model shown)

 

USB type B is $1.07 but it takes up a lot of space. And I know the shortest type B cable I can lay hands on here is 15 feet long.

 

I think I will put in a pad for USB micro but leave it unpopulated. Its probably a horrible idea to use it. Also, it wouldn't have an off switch - that switch disconnects the 7.5V.
 

The audience is someone who may already have a Pi3 - which has a microUSB power jack. So they already have found high-quality 5V supplies, likely 1.5 or 2A.

 

Here's the evolving model, with a USB B dropped in on top of the PLD  chip. I can't fit it in. (no it can't have that spot behind the voltage regulator) (the 3D viewer adds some board under things- the blue line is the real edge)

 

 

Also I can't believe those nice right-angle switches cost more than $1 new and 0.50 surplus. The vertical kind are 10 cents. 

[wierd_w]

Yup. Total space hogs they are.

 

If you can't fit it, don't sweat it.  Just I dislike the fully SMT micro USB ports, because they lack good anchoring. If it's what it ends up with, I will begrudgingly accept it.. But as an alternative, can you give a 2 pin header internally instead?  You could probably squeeze that in at the back end of the card, where the LEDs and transistors are living.  I could bridge off the Pi's 5v rail that way. (Pi has direct connect to its 5v rail on its GPIO header that I could bridge to. That way the Pi's power adapter could drive both units, without injecting power onto the sidecar bus.)

 

another interesting tidbit;  the Pi can be powered by those pns as well.  This might let you control the startup sequence.

Edited November 19, 2019 by wierd_w

[Tursi]

Agreed on the fully SMT USB ports. That's what we used on the Jaguar Skunkboard, and countless people ripped them off the boards, sometimes damaging the surrounding area (sometimes repairable).

 

[+FarmerPotato]

1 hour ago, Tursi said:

Agreed on the fully SMT USB ports. That's what we used on the Jaguar Skunkboard, and countless people ripped them off the boards, sometimes damaging the surrounding area (sometimes repairable).

 

 

Here's the one I learned of from the KiCad library. It has a pleasant dead-bug shape. The PS4 has HDMI connectors in this style. (my first SMD practice) 
 

 

Wurth Electronik 629105150521 

It costs $2 at Newark

 

[tdididit]

Are you mean something like this ?

 

Soon should be available at arcadeshopper.com

 

Edited February 2, 2020 by tdididit

[Omega-TI]

That's Purdy!  I might have to print up that colorful thing up, slap it in a frame, and hang it up in my den!

 

Question... it projected to be the EXACT physical size as the 32K expansion?  Many people already have cases, so that would be a big selling feature.  

If/when it comes to pass, I can see a glut of used 32K's coming to market.

[tdididit]

11 minutes ago, --- Ω --- said:

That's Purdy!  I might have to print up that colorful thing up, slap it in a frame, and hang it up in my den!

 

Question... it projected to be the EXACT physical size as the 32K expansion?  Many people already have cases, so that would be a big selling feature.  

If/when it comes to pass, I can see a glut of used 32K's coming to market.

Yes, It was one of the targets to make it exacly like Sidecar 32k - same board size, plugs, led, drills are in same place so it will fit in 32k + TIPI case.

No need 32k sidecar anymore because you will have 1meg

Edited February 2, 2020 by tdididit
type-os

[tdididit]

... and it wasn't easy to shrink PEB card to sidecar 32k tiny board - it tooks 24hrs with CAD app 

[wierd_w]

3 hours ago, --- Ω --- said:

That's Purdy!  I might have to print up that colorful thing up, slap it in a frame, and hang it up in my den!

 

Question... it projected to be the EXACT physical size as the 32K expansion?  Many people already have cases, so that would be a big selling feature.  

If/when it comes to pass, I can see a glut of used 32K's coming to market.

 

If he releases it as a vector, I can grant that wish in large format.

[Omega-TI]

14 minutes ago, wierd_w said:

 

If he releases it as a vector, I can grant that wish in large format.

Oooooh?  How large?  How much?  PM me!

 

[wierd_w]

up to 36" wide on the short edge.

 

But I need a vector image to do that justice.

[tdididit]

Final SAMS board preview. 

I've just checked again both layers and added "wrong polarity" protection

 

 

[HOME AUTOMATION]

Hmmn...

 

It looks as though you have placed a diode in series with the main GND.
Diodes reduce the voltage by at least .7vdc, closer to 1v with a decent load. This will work under good conditions, but the TI-99/4As supply will be different, at +5v. Perhaps a larger concern is that it appears you have placed the diode in the GND path, this will add switching noise to the GND path! and will cause the console's GND to be at a slightly different potential! This may force current to leak from the console into the memory board, along unanticipated paths.

 

I strongly advise a different course for polarity protection.

 

Perhaps a fuse in series with the V+, followed by a large enough diode to "short out" the reverse current and blow the fuse.

[pixelpedant]

You know, if a sideport SAMS becomes available just as Adamantyr's RPG (Realms of Antiquity) reaches release, it really is proof that god loves us, and Adamantyr is his prophet. 

 

I mean, how cool is it that there's already a "killer app" with a lot of mass appeal ready to go, just as SAMS looks to become the latest TI tech to reach a level of accessibility sufficient to the masses (there are dozens of us!)

[GDMike]

Doesn't help the NanoPeb..

we need a fix for NanoPeb to use SAMS..

[Omega-TI]

I believe it's called an upgrade (to something else).  It's quite common in the computer consumer market when people outgrow what they are currently using.

[GDMike]

Lol,, yes we need a fix for the nano since AMS was already available when the NanoPeb came out..but wasn't included to support..

[pixelpedant]

One reason there still might be a future for a Nano/CF7 equivalent is just that TIPI+SAMS still doesn’t give you an RS232 port.  I know I’m in the minority here, in using RS232 for a whole heck of a lot (for talking to a whole “network” of RS232 devices).  But it’s one thing that keeps my NanoPEB plugged in most of the time, and my TIPI on the shelf most of the time. The ultimate solution to sidecar peripheral expansion, to my mind, offers SAMS+Disks+RS232.  You could certainly do something via TIPI which makes TIPI service scripts the “RS232 device” (just via a PL2303 adapter or whatever). But I feel like the dream is SAMS, and Disks, and fully legacy compatible RS232 (which obviously, the NanoPEB doesn’t quite get us as it is). 

[GDMike]

Well I have to second all that, I mean shoot, for the location of the NanoPeb, and I Know nothing about design, BUT it seems so obvious that adding a through bus to that Nano adding SAMS in between with Tipi at the end doesn't that make more sense?