Arty A7 35T - USB broken

[awolf]

Hi, i have broken the micro USB connector J10 on my Arty A7-35T board. I want to try to repair the D+ D- USB lines but since the board design files are not available i cant see where the usb traces on the boards. Could you at least publish a screen shot of PCBN traces connection between USB and FTDI USB controller?  

thanks

Edited October 11, 2021 by awolf
typo correction

[JColvin]

Hi @awolf,

I'm not readily able to provide the specific PCB traces you asked for, though I did take a picture of the traces on the board itself in case that helps you.

Thanks,
JColvin

[cnegrea]

My Arty had a similar  fate. From the image above one can see it is quite hopeless, unless you can solder small wires directly on FTDI chip pads.

It looks bad, but it's back to life, again. I lost all pins, Ground is easy, positive, from the 5V rail.

[asmi]

3 hours ago, cnegrea said:

My Arty had a similar  fate. From the image above one can see it is quite hopeless, unless you can solder small wires directly on FTDI chip pads.

It looks bad, but it's back to life, again. I lost all pins, Ground is easy, positive, from the 5V rail.

OMG, what the heck were you doing with that board?

[cnegrea]

22 hours ago, asmi said:

OMG, what the heck were you doing with that board?

Tried to save the board,  secured with a lot of epoxy, better an ugly working board than a pretty broken one. I had to connect two USBs(program+comm) and power barrel connector before.

Edited December 11, 2023 by cnegrea

[asmi]

On 12/10/2023 at 2:12 PM, cnegrea said:

Tried to save the board,  secured with a lot of epoxy, better an ugly working board than a pretty broken one. I had to connect two USBs(program+comm) and power barrel connector before.

I meant what was you doing with it that caused USB port to be ripped out? That's gotta require some serious force. This devboard is designed to be used in a lab, as it doesn't even have mounting holes if my memory serves me. Devboards are supposed to be used for prototyping, before spinning out a custom board specific to your application, and that board is supposed to have proper mounting provisions (hole pattern, physical size & shape, etc.). Not sure what you used epoxy for.

[zygot]

asmi: "I meant what was you doing with it that caused USB port to be ripped out? That's gotta require some serious force. This devboard is designed to be used in a lab, as it doesn't even have mounting holes if my memory serves me."

I can't tell you how many development boards I have in which those surface mount USB connectors have ripped off. For some, it's definitely stress from insertion/removal of a USB cable over time. You can't leave the cable plugged in them because that'll put stress on the flimsy top layer copper pads. Even putting a duplicate pad on the opposite side of the pcb and inserting lots of vias would help somewhat... though would negate the cost of the proper connector. You can't perform lots of insertion cycles for the same reason. I don't buy boards with USB connectors, unless they have through-hole tabs anymore.

Using smt connectors that don't have through-hole tabs saves almost nothing in production costs and greatly hinders the product lifetime.

A different opinion. Edited December 12, 2023 by zygot

[asmi]

14 hours ago, zygot said:

Using smt connectors that don't have through-hole tabs saves almost nothing in production costs and greatly hinders the product lifetime.

Actually it saves quite a bit because TH parts are often soldered manually, and so you pay for each individual TH part that you have on a board. Which is why many manufacturers now experiment with reflowable TH parts. Thought most modern USB SMT connectors have semi-TH tabs which can be soldered via reflow for additional mechanical strength.

Edited December 12, 2023 by asmi

[zygot]

Asmi, Let's go with your premise that using USB connectors with through-hole tabs entails significant costs over smt connectors. All of Digilent's FPGA boards use through-hole connectors for the PMODs. So, either through-hole components can be done by automation equipment or not. I'm not buying the argument that good USB connectors with through-hole tabs have to be hand soldered anyway.

So, what it comes down to is a vendor cutting a buck or two off of the assembly costs by using smt USB connectors should prominently advertise that fact that the products have very limited cable insertion cycle lifetimes under normal usage rather than do it correctly and charge a couple of bucks for a much better product.

Of course no one is going to tell a customer that they have so little disregard for the customer, so they just go ahead and make products that have a good chance of premature failure due to one stupid decision. Reminds me of the cost saving measures of almost every auto maker using an airbag inflation initiator vendor whose products just happens to explode some of the time. Years later, after many unnecessary deaths, there's a giant recall... Of course no one is going to die from a broken-off USB cable connector. Neither is anyone going to force a recall for what may be considered a defective product if its an FPGA development board.

My assertion is that no customer is going to choose to buy a board with an smt USB connector and likely to be ripped off by normal use after a year or so, over a reliable USB connector that costs a buck more. It's no way to treat a customer that you want to keep. This are especially true for a product designed, not for engineering lab use, but specifically for educational student use.

I say shame on vendors who abuse their customers with bad design choices, and then hide it from prospective purchasers. Shame on vendors who just don't care. Edited December 12, 2023 by zygot

[asmi]

4 minutes ago, zygot said:

So, what it comes down to is a vendor cutting a buck or two off of the assembly costs by using smt USB connectors should prominently advertise that fact that the products have very limited cable insertion cycle lifetimes under normal usage rather than do it correctly and charge a couple of bucks for a much better product.

It's a well-known fact that micro-USB connectors are not very reliable, so those customers who care about this should just stay away from products which use micro-USB. Incidentally I haven't ripped out a single micro-USB connector in my entire life, but I still moved all my new designs to USB-C because it's just more convenient to use.

 

7 minutes ago, zygot said:

My assertion is that no customer is going to choose a board with a reliable USB connector that costs a buck more than one with an smt USB connector and likely to be ripped off by normal use after a year or so. These are especially true for a product designed, not for engineering lab use, but specifically for educational student use.

Your assertion is meaningless because nobody in their right mind will do two separate spins of the same board with different connectors. And since A7 board was designed at a time when USB-C wasn't a thing, their options were a (relatively) big and bulky TH mini-USB, or an SMT micro-USB (I don't even know if TH micro-USB connectors ever existed, much less at that time, because their chief value proposition was that they were smaller and so it takes less PCB area). Also A7 PCB is quite high-hech even by modern standards, consequently back then it was pretty much a bleeding edge, so it must've cost them a fortune to manufacture and assemble them all those years ago (even today placing 0201 and 01005 usually commands a premium). WIth that in mind saving PCB space wherever they can must have been a strong motivation. Why haven't they redesigned the board more recently to use modern connector is a good question, which probably comes down to cost as well - PCB engineer's time is very expensive, so their calculus probably was that it's not worth it.

[zygot]

asmi,
If you want to defend bad design choices, that's your privilege; I choose to call them out.

There's no point to continuing this little debate, so I 'll just stop with this thought, in the context of all of your arguments. The Raspberry Pi3 has a micro USB connector... with through-hole tabs. The RPi4 has 2 micro HDMI and a USB C connectors, all with through-hole tabs. These products are on very densely populated, very small PCBs, and retail for under $50 in single quantities. No one's complaining about connectors being ripped off of these products. That's just on example of well thought out product design, because the people making them care about their customers. I have lot's of cheap development boards with quality components that counter your arguments. Edited December 12, 2023 by zygot

[cnegrea]

On 12/11/2023 at 3:49 PM, asmi said:

I meant what was you doing with it that caused USB port to be ripped out? That's gotta require some serious force. This devboard is designed to be used in a lab, as it doesn't even have mounting holes if my memory serves me. Devboards are supposed to be used for prototyping, before spinning out a custom board specific to your application, and that board is supposed to have proper mounting provisions (hole pattern, physical size & shape, etc.). Not sure what you used epoxy for.

Well, I am not at that level, I use this board for small projects, like an Arduino. I am learning, so I would abuse this board. Epoxy is to secure the wires, they are 5mils in diameter. This board is very well designed. Since the FTDI schematic is not public, I assumed the big capacitor near the USB is 5V, but it is 3.3V.  The board took it gracefully, until I noticed the power supply part is hot. It works well, now.