Hardware failure

Questions on other types of hardware and getting it talking to the ARM CPU
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w0ivj
Posts: 10
Joined: Sat Nov 09, 2013 2:43 pm

Hardware failure

Post by w0ivj »

I previously ordered a super pro board and everything was working fine. I am supplying it with a regulated 6 volts. Today I turned it on and it was drawing too much current. I removed U2, C15, C4, C5, and C6 but still have a 10 ohm resistance between VDD and GND. I think the problem must be in the LPC1756. I was not powering any IO devices separate from the CPU. Do you have any repair suggestions? If you think it is the CPU that failed, and the failure was just an anomaly , I am willing to purchase a new LPC1756 that has been loaded with BasicTools and install it myself if the loaded LPC1756 is not too expensive.



basicchip
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Re: Hardware failure

Post by basicchip »

We don't offer bare LPC1756s with BASIC loaded, and it takes a skilled technician probably 15 minutes to replace one with the right tools (me it would take an hour or more, and I have most of the right tools -- hot air station, microscope, fine tip soldering iron).

LPC1756s have proved to be pretty sturdy, and we routinely abuse them, and most of the time they survive it. But sometimes they don't. What constitutes abuse -- inputs driven with low impedance sources while the power supply is off, over voltage >5V, or negative voltages >1V, static, probably others. Just FYI there are a few thousand SuperPROs out there and we see only a handful of part died failures.

To give a good answer as to what happened to yours, I would need to know a lot more about your setup. What is it connected to, how is it powered, ...

We have done a couple post mortems on failed boards, and we have found chips that still functioned but IOs blown (probably overvoltage), bad soldering by the user, including lifted traces by too much heat.

w0ivj
Posts: 10
Joined: Sat Nov 09, 2013 2:43 pm

Re: Hardware failure

Post by w0ivj »

Thanks for the reply. I am supplying 12 V to 3 regulators simultaneously. The LM7806 supplies the SuperPro; the UA78M33C supplies an oscillator chip with only I2C connections to the CPU; the LM7805 with a diode in series supplies 4.3 V to an optoencoder with 2 connections to the CPU inputs. There is also a display but it is only driven from the CPU. With this setup, I don't think it is a power sequence problem. It may have been static discharge but I have been working with electronics for over 60 years and have yet to attribute a failure to static discharge. Maybe it was just an anomaly. I have ordered two more SuperPro boards for replacement. I do not expect you to troubleshoot this situation but I am including a partial schematic for your own benefit.

I do feel that the processor is bad. I removed the 3.3 V regulator and bypass capacitors and supplied 3.3 V from a current limited supply. Using my IR thermometer, the LPC1756 heated up to 63 degrees C with the voltage pulled down to 0.8 V at about 900 mA whereas normally it would be around 30 degrees C. I was able to remove the CPU chip but probably won't pursue this any further.

Thanks for your help
Attachments
ARM SI570.pdf
SuperPro board use.
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basicchip
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Re: Hardware failure

Post by basicchip »

It looks like power is not the issue in your circuit. I would comment that you could have fed the 5V into the 5V Arduino pin (next to the 3.3V pin) and saved yourself a regulator.

Depending on the total load, you might consider using an OKI78SR to convert from 12V to 5V. It will save a lot of heat, and heat can cause reliability issues (it is a switching regulator)

basicchip
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Re: Hardware failure

Post by basicchip »

I'm going to post the whole email conversation here, as I think it is instructive --

------------------------------------------------

If you want to buy a 1756 from Mouser/Digikey and put it back on the board, I'll give you a firmware update file.

However, if that doesn't work, it doesn't work.

While I know from some hobbyist perspectives time is free, but I don't look at it that way myself, and from the business side we wouldn't survive doing too much free engineering.

When I buy a board to do experimenting on from someone else, I always buy 2. Most electronics these days are in the <$50, so better to have a spare, and while I might spend 15 minutes trouble shooting a dead board that is about my limit and if it isn't something like a diode/resistor/cap that is blown it gets junked/canabalized.

As for static, I have seen it kill electronics. Maybe the industry has gone overboard, but to maintain ISO9000 certification, they have everyone wearing anti-static coats, anti-static mats, wrist straps that are checked routinely and ... So I assume some studies have shown if static doesn't outright kill a board, it can affect reliabilty.

Just FYI, I've been doing this for 50 years, started soldering at Franklin Institute classes in Phila.

brucee

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Thanks, Bruce but I already have 1300 lines of code written for the SuperPro. I have ordered 2 SuperPro boards to replace the one with the bad CPU and give me a spare. It doesn't sound like repairing my bad board is feasible although I have already successfully removed the LPC1756 and I think I have the tools and skill to replace it.

Tom

----------------------------------------------------

Hi Tom-

For low volume like your radio project the smallest interchangeable piece is the SuperPRO.

We have done low count firmware updates in the field, but invariably we end up spending an hour or more with the customer getting their system able to download code. So a $49 SuperPRO is still cheaper from our perspective for those situations than a $10 firmware upgrade and having to spend a few hours of our time.

The BASICchip at $10 is the way to go if you want to use a pre-programmed chip.

brucee

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Hi Bruce,

Does this mean that if I want to imbed an LPC1756 into my amateur radio project or repair my SuperPro board with a bad processor it would cost a minimum of $500 to buy the ability to program in system?

Thanks,
Tom

--------------------------------

We don't offer programmed QFP parts and don't intend to. We would have to buy a couple hundred dollar ZIF socket, get special packaging and ... Doesn't make much sense.

We do offer to OEMs the ability to program LPC1756s in system with a licensing fee of $5/unit, sold in blocks of 100,1000, and unlimited.

brucee

---------------------

What is the cost of an LPC1756 chip programmed for BasicTools?

Thanks,

Tom

w0ivj
Posts: 10
Joined: Sat Nov 09, 2013 2:43 pm

Re: Hardware failure

Post by w0ivj »

I was able to successfully remove the LPC1756 processor from the board and install another LPC1756 that I ordered from DigiKey. I ordered the firmware update program and installed the firmware. Everything seems to be working fine. Thanks for all the help.
Tom

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