USB connectors

If you're having problems with the hardware of a DM41X or DM42, post about them here.
x55
Posts: 16
Joined: Sun Jul 26, 2020 7:32 am

Re: USB connectors

Post by x55 » Mon Jul 27, 2020 2:04 pm

cdmackay wrote:
Tue Jan 08, 2019 9:05 pm
I had read that the power pins of the USB connection may be slightly longer, so that power is up before the data pins are connected. Whether that's true or not, I don't know, and I think it referred to the USB-A (i.e. PC/host) end.
Yes, it refers to USB v1 Type A 'plugs'. On inserting the plug the grounded metal shield makes contact first, then the longer 'pins' establish a steady power supply (in a USB connection the 'host' always supplies the power), then the data lines are connected. In MiniUSB and MicroUSB connections there are no 'longer' pins but a fifth ('ID') 'pin' that, in conjuction with some simple electronics, is used to determine which is the host and prevent conflicts that way. MiniUSB and MicroUSB 'receptacles' can also come in an 'AB' format that accepts either type of plug and utilizes the ID 'pin' to sort out which is which in "On the Go' connections. In charge-only cables the data lines should be shorted out at the device.

In USB connector are there no 'pins', but flat strips positioned against a solid substrate to form an arrangement that makes the connections much more robust and durable (no actual pins to get easily bent or broken). Also, where possible stress points are moved into the cable, which makes for easier and cheaper replacement if wear does cause a problem. In terms of durability, v1.0 connectors are the least rated, then Mini connectors then Micro connectors, with C connectors providing the highest specification. Each one of that sequence is about an order of magnitude more durable than its predecessor.

E&OE.
--
HP: 55/67/41C/HP-IL/ProtoCODER*/41CL/MLDL**/41CX/16C/71B/42S/33s***/35s ...
DM: 42 ...
Etc: If a calculator has equals, why buy one unless it's the cheapest?
* ProtoTECH, USA / ** Eramco, Netherlands / *** Carly Failurina model

cdmackay
Posts: 152
Joined: Fri Oct 05, 2018 8:33 pm
Location: Cambridge, UK
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Re: USB connectors

Post by cdmackay » Fri Aug 14, 2020 11:09 pm

thanks!
Cambridge, UK
41CL/DM41X 12/15C/16C DM15/16 71B 17B/BII/bII+ 28S 42S/DM42 32SII 48GX 50g 35s 30b/WP34S Prime G2
& Casios, Rockwell 18R :)

Alessandro
Posts: 1
Joined: Sat Oct 03, 2020 10:04 am

Re: USB connectors

Post by Alessandro » Sun Oct 18, 2020 11:48 am

Hi all,
I received my new DM41X (s/n 501) and it gives a very good keyboard feedback.

I am experiencing USB connection issue, even after cutting the plastic shell of it as mentioned in this post.
My Win10 reports a "device descriptor request failed" inside the USB controller (control panel) and I do not have any chance to see the drive.
Do you have some suggestions?

Thank you,
Alessandro

ljf2
Posts: 1
Joined: Wed Apr 29, 2020 11:37 am

Re: USB connectors

Post by ljf2 » Wed Oct 21, 2020 11:29 am

I had the same problem with my new DM42: it dit not mount, be it on MacOS or on Linux file system). I solved the problem by removing even more plastic from the USB connector (approx. 2 mm in all). 100 % successful connections ever since.

It seems to be an issue that cannot be solved with the current design of the board.

cdmackay
Posts: 152
Joined: Fri Oct 05, 2018 8:33 pm
Location: Cambridge, UK
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Re: USB connectors

Post by cdmackay » Wed Oct 21, 2020 8:42 pm

It's been pointed out in other threads, but note that not all micro-B cables have the same length connector.

I just compared lots of mine, and selected one that was the longest. Worked perfectly with my DM41X. I've had problems with randomly selected cables before, including trashed FAT disks.

You can test it in the calculator; before enabling the USB disk, make sure that the connector protrudes slightly from the calculator case. If you think that the case is touching the plastic of the connector, and stopping it travel far enough into the calculator, find another cable, or trim some of the black plastic.

I wouldn't rely on the power symbol on the calculator, since the power pins may contact first, but it's the data pins that are important here. I think that may be only for USB-A, perhaps, but I prefer to verify it visually and by feel.
Cambridge, UK
41CL/DM41X 12/15C/16C DM15/16 71B 17B/BII/bII+ 28S 42S/DM42 32SII 48GX 50g 35s 30b/WP34S Prime G2
& Casios, Rockwell 18R :)

nephilim
Posts: 10
Joined: Sat Sep 12, 2020 10:09 pm

Re: USB connectors

Post by nephilim » Wed Oct 21, 2020 8:45 pm

I can confirm that the USB connector of the following cable can be fully inserted w/o touching the DM42's case. https://www.amazon.de/gp/product/B07JB6V66H. I had to wait a few weeks but the wait was worth it.

Borrowed from amazon...Image

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