Electronics > Repair
Reverse engineer Dallas DS1742W?
james_s:
--- Quote from: Tantratron on November 12, 2020, 05:32:04 pm ---I'm bit lost here due to my non-native english speaking or not grasping 2nd message.
What exactly do you recommend as a method solve the issue ?
By the way, the same issue occurs in older tektronix, see this synthesis https://www.eevblog.com/forum/repair/nvram-of-oscilloscope-tdsxxx-serie-c-and-d/ so could it a universal new design chip with firmware able to accommodate different brands of DS or Maxim ?
If we want to keep these legacy oscilloscope, the problem number one is these DALLAS nvrams potted battery so it would nice to have a plug&play board with ease to change battery and emulating the same RTC and memory function
--- End quote ---
New replacement using currently available parts, at least it works in TDS3000 scopes.
https://github.com/james10952001/DS1744WP-to-DS1742W-adapter
Or you can cut into the original Dallas brick and solder in a new battery, looks a bit messy but is not too hard to do and usually successful.
sicco:
Happy to report that my plugin module for TDS3000 works OK now. This unit fits inside the Tektronix scope expansion connector (rear panel slot), and as a bonus you get the serial port with it as well. Micro USB and FTDI chip on board if you prefer that instead of legacy DB-9 serial ports. Or just TTL level serial for a FTDI-TTL 6 pin header adapter.
Maxim/Dallas DS1744W module on this plug-in takes over the role of the DS1742W on the main board.
Still needs a bit of patch wire soldering on the main board unfortunately: the DS1742W /CS pin, or D4 from the PowerPC XPC860DCZP, that I routed to pin 11 of the 100 pin expansion port connector. That is/was EXTCLK_in from the PowerPC CPU, but I stole it, and now use it as a spring board. That pin 11 used to go via a 100 ohms SMD to the PowerPC CPU, I unsoldered that resistor to free up this connector pin. Next, if you'd leave the old DS1742W on the main board, it needs to be silenced. Did that by pulling its /OE to its VCC, and cutting the PCB track that used to go to that /OE.
It also can accommodate an ESP32 DevKit, and the WiFi web server as disclosed in https://www.eevblog.com/forum/testgear/reverse-engineering-tektronix-tds3gv-module-for-tds3000-series-oscilloscopes/msg3014688/#msg3014688 works great, thank you stas_last!
It also helped me upgrade my TDS3034 into a TDS3054, as per https://www.eevblog.com/forum/testgear/reverse-engineering-tektronix-tds3gv-module-for-tds3000-series-oscilloscopes/msg2748914/#msg2748914 - thank you for that james_s - and thank you for the hint on DS1744W in the first place.
This board could only be realised with the great guidence from pmercier c.s. as per https://hackaday.com/2020/07/18/reverse-engineering-teaches-an-old-scope-new-tricks/
Only bit I could not get to work (yet) is the 10BaseT Ethernet port. I assumed in full ignorance that all that was needed was a PHY chip like the legacy MC68160 but looks like more is needed on the board - likely a ROM and possibly something for the MAC address maybe. Not too big a problem, as Ethernet on the TDS3000-b and beyond comes from the mainboard now, and -b will reject a plugin board that says it's TDS3EV. So let's not do that.
Yes, this solution to the TDS3K RTC empty battery design flaw is obviously more expansive as the james_s patch board, but on the plus side this is much easier to retrofit I think - unless you're really good at desoldering 24 pin DIP modules from delicate multilayer boards. And you get the serial port. WiFi web server. USB serial. Unlock the 500 MHz bandwidth for free... Unless you had a serial module already of course.
So no more end of life after 20 years for TDS3000. Another 100 years to go - well - for as long as you can get DS1744 clip-on batteries (which btw have easily accessible solderalbe battery tabs).
Should I start a business selling these boards now?
james_s:
I have an original Tek ethernet module, I can open it up later and see what it has inside.
sicco:
Wow. Yes please!
james_s:
This is the board in a TDS-3EM module. As hypothesized there is a ROM in there. I don't really want to try desoldering it and I don't think I have an adapter to read that package with anyway. It may be possible to dump the contents onto a floppy or via GPIB.
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