| Electronics > Repair |
| Reverse engineer Dallas DS1742W? |
| << < (11/15) > >> |
| friendtogeoff:
Wow, really nice piece of work @sicco. I'm interested in getting one of these to put into a TDS3054 (not B or C) as an alternative to buying a TDS3EM from the sharks. Any hints on where to find the eBay offer? |
| sicco:
I have two that are fully populated and tested, as per picture. Looks like my eBay ad for them from ~November has disappeared, but happy to sell and ship directly to you. 150 EUR for one, plus 20 EUR shipping to a UK address. Not sure what customs duty get added for you post Brexit, but obviously that for you to settle. Paypal should work, IBAN maybe even better. Share your shipping address etc via direct message please (instead of full forum post). Warm regards, Sicco. |
| sicco:
PS just noticed that on the picture I just made, there was a board plugged in that does not have Ethernet (TDS3EM emulation), but the two units in front of the scope will give you Ethernet as in: |
| cuebus:
Hi all, I decided to definitively figure out how these DS1742Ws are constructed so I softened the epoxy on the one I desoldered from my scope and got to work. Turns out, unlike the DS1486 that I reverse engineered last year, this one uses a single chip solution. Both the RTC and RAM are on the same die. This part is a TSOP-1 32 pin part marked Dallas DS1743E-3 (the 3 is the voltage designator, there is also a DS1743E-5 for 5V chips). As you can expect it's the same part used in the DS1743W, which is 8 x 8k, just 2 address pins are unused, similar to james_s' adapter board solution. Battery used is smaller- just a BR1225 coming in at 48mAh. One may think this is an issue but I measured the current draw in data retention mode to be only 300nA, giving it a lifetime of 18 years unpowered. My scope is from 2000 and has 50,000 hours on it, so not counting self discharge, my original chip would have had a life of about 4 years left still unpowered. Pinout of the TSOP is close but not the same as JEDEC standard since naturally there need to be some pins there for the RTC xtal and battery inputs. If you can acquire a DS1743WP PowerCap (some available on eBay), you can do what I did and remove that chip (it's the same one) and solder it onto a PCB made to copy the DS1743W layout. I attached the gerbers of the layout I made. The chip on the powercap is tacked with adhesive on 4 edges, but they are right on the edge of the chip so can be relatively easily cut away with a knife. As long as you get most of it off you'll have no issue removing the chip. You only need 2 other parts, a crystal, and a battery. I used the same crystal as for my DS1486 project, CMR200T32768DZBT I don't know the load capacitance required by this one but I've had it running several days in my scope now and it's still exactly on spec with another clock. Battery for my board is BR-1225/H1AN. As stated, you'll get 18 years minimum use with this. Altogether it makes for a nice compact replica, and fits like a glove. Cheers, Robin |
| james_s:
Well that fits what I could see in the xray picture of mine. Interesting that the IC is a DS1743. |
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