# Tag Info

55

Take the best pictures of both sides of the board that you can. You can use a scanner to scan the bottom side of the board, but not all scanners will be able to focus the top layer because of the height of the components. To this guide I used a 3MP camera of the iPhone 3GS without any special lighting or anything. You will almost always likely to ...

38

I would have done the same design, in order to reduce dynamic and static load regulation error. The details for the reasons are evident in the datasheet. look at dynamic load regulation error and input step regulation error. I can only guess what error budget the designer had in mind, but it common for every LDO to have the above responses , although this ...

25

That MOS 5717 thing is most likely a microcontroller or some part that executes code. It needs a clock to run. However, just a clock for a micro doesn't need crystal accuracy. That is probably for communication. USB requires a fairly high-accuracy clock. A mouse doesn't need to track real time, and there is no reason for it to be in sync with the CPU ...

24

Are there techniques an electrical engineer could use to verify that a circuit actually performs the operations described in its spec, and no other operations? In theory, yes, I think this is possible. However, for a complex CPU it will take a lot of time and money. Also, if you do not fully know and understand the design, you will be unable to judge if any ...

23

It is not only the number of pins used to read a keypad matrix that matters. One thing to consider is the number of crossings of traces, i.e. the number of vias needed. Each one needs a hole to be drilled and this process was not as much automatic in the seventies as it is today. But, this is not the major point here: A 4x5 matrix following the geometrical ...

23

It is most likely a low-voltage low-current glass gas discharge (GGD) tube. It will not conduct at all until a certain voltage is reached, then the gas ionizes and it become effectively a short circuit until the current is removed. This small size is to suppress back-EMF, that is short-term low-current pulses. These devices can have capacitance values as low ...

23

It's most likely a type of fiducial marker, used by a pick-and-place machine to correctly place the SMD parts on the copper side of the board.

21

The MOS 5717 has quite a bit of independent work to do on its own to create the mouse functionality from a set of optical encoders. The description from the datasheet states it the best as, The 5717 is a custom CMOS mouse controller for the Commodore 64. It will be housed in the body of a two button mouse, enabling it to be plugged into ...

16

Yes, all PCBS have schematics. The ones that are public include Open Source Hardware Very simple designs are often based around an example schematic provided in the data sheet of the primary IC. You can usually obtain the data sheet from the IC manufacturer. Bus Pirate AD603 Data sheet However, as other answers point out, the majority of schematics ...

14

Specifications for this particular chip (SPCP168A) don't show any explicit serial/SPI port. Also, there is no indication in blogosphere that this particular chip has any field firmware update options. So it is very likely that it runs from a mask ROM. However, there are other optical mice on the market, they are based on the original patented Avago ...

14

The best paper I have read on the subject is "Stealthy Dopant-Level Hardware Trojans" (Becker et al) from 2014. Since the modified circuit appears legitimate on all wiring layers (including all metal and polysilicon,) our family of Trojans is resistant to most detection techniques, including fine-grain optical inspection and checking against “golden ...

13

This is known as Chip-On-Board (COB) technology, the black material is epoxy resin, it is the same as the black material on ICs. Note than the bonding wires encased in the resin are very thin and fragile. COB technology is sometimes used to prevent reverse engineering. This YouTube video demonstrates a process for removing the resin packaging on ICs using a ...

12

Of course it's possible. There are many companies that provide these services. The real question is whether or not you could do this at home. You might get away without needing a SEM (Scanning Electron Microscope), that design might be done in ~3u geometry which would imagable using visible light. You'll need a wet bench to etch off layers, like HF for ...

12

I've seen some schematics where the LED is on a path used to power a circuit (or part of). It means if you remove the LED, the current won't flow, and the circuit won't work anymore. Look at this one: If you remove the LED, the circuit that is connected to CNTLED won't be powered by IC22C anymore. So, it depends on how it is implemented. If you don't know ...

12

I'm not even sure the MCU inside that IC has programmable memory at all – maybe a few bytes to set a custome USB Device and Vendor ID, but that's probably it. (Rest would be ROM) I'm fairly certain it's designed specifically in a way that calculates the relative motion directly from the camera observation with hardware; that's very easy to design into ...

11

The first solution should be to stockpile the discontinued IC before it completely dissapears. Contact the IC manufacturer directly and scour their distributors. There are also component brokers that specialize in discontinued parts. Buy everything you can find. Depending on the price of the chip an order of ten thousand might be worth a specialty run ...

11

Look at it this way: No matter which path you choose, you are reverse-engineering the old design. Before you can build a new chip, select a new off-the-shelf chip, or design a new PCA, you will first have to determine what are all the behaviors, features, and characteristics of the old design that need to be reproduced in the new design. You'll need to ...

11

It's fairly easy to write an I2C "ping" utility for a microcontroller. All you need to do is scan through the ~128 addresses and for each one: Send I2C Start condition Send a single byte representing the address, and get the ACK/NAK Send the stop condition. If there is an ACK (the data line held low on the 9th clock cycle) then a device with that address ...

11

It is a BT2.0 + EDR Slim Module similar to FCC ID MSQBT183 (Use the FCC OED ID Search for photos and some documentation). It has Implement 802.11 coexistence solution by AFH (Adjacent Frequency Hopping), WCS (Wireless Coexistence System), and Bluetooth Priority. The FCC documents show a similar board without the usb points labeled, but that's most likely ...

11

At this writing, there are two "answers" that are total guesses - and wrong at that too. These comb structures are as you might expect to see when you want to induce breakdown at a precise location and into controlled structures rather than else where in the chip. These are in the TOP metal layer, the combs are there to give lots of sharp edges to promote ...

11

It's perfectly legal to open up a chip and try to figure out what it does and how it does it. Good luck. I have done that to competitors' equipment to see whether they infringed any of our patents (some did, some didn't). It's illegal having done that to copy the chip and sell the results. Regardless of whether anything inside it is patented, the whole chip ...

11

Q3 and Q4 are not "Diode connected". They are arranged as emitter followers to reduce the error that would result from the base current for Q1 and Q2 being derived from the current reference flowing through R2. The gain of Q3,Q4 will reduce the current required by a factor of Hfe**2 (maybe 10,000 times) so that virtually all the current from R2 flows ...

11

X2 drops the voltage--it has impedance $X_C = \frac{1}{2 \pi f C}$. R in series limits the peak current. R2 in parallel bleeds the voltage off the capacitor so you don't get a jolt if you touch the pins after it is unplugged. The zener limits it to the 48V or thereabouts when the relay is off. Probably the relay limits the voltage when it is on. The 1....

10

In general there are two main problems with reverse engineering: patents and copyrights. For US, it is often said that only the actual component layout is covered by copyright and you'll have problems if you directly copy it. The patents on the other hand protect the idea itself and the patent descriptions try to be as broad and vague as possible in order ...

10

The best answer is always "talk to a lawyer." That being said, you could check out any kind of license agreement you may have implicitly agreed to when you purchased the item. Since you are not marketing this modification, the worst that could happen is that you could get a takedown request/notice for the video or a cease and desist letter. Odds are, the ...

9

If you don't want to do it manually: Hook up a Raspberry Pi Run sudo i2cdetect -y 0 If Run sudo i2cdetect -y 0 does not work, Run sudo i2cdetect -y 1

9

I'd say most of the PCBs do have a schematic somewhere, and it would greatly improve the understanding of the PCB and the functions of all the parts if it was available. Especially giving all the intended sizes and ratings of the small parts (resistors, capacitors). But it contains the essence of the circuit and quite often many years of experience ...

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