Model compatibility #27
Replies: 7 comments 8 replies
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Absolutely OK, thanks for opening up the first discussion!
The A168 is almost certainly not compatible. The EL backlight gets its power from two exposed pads on the circuit board, which (based on my limited understanding of EL) would likely have to be boosted to a higher voltage. It's possible the A168 may be using the same LCD, but inside the case the geometry isn't the same, so I doubt the Sensor Watch PCB has everything in the right place. It also lacks the driving circuitry and exposed pads for the backlight. The GMW-B5000 is definitely incompatible; I can see at a glance the LCD is very different. Having said that, if you have one and want to put some effort into reverse engineering, I offered some tips and tricks in this talk at Hackaday Remoticon.
I do not know, but if I were going to try it, that's likely what I would do. In fact, the Casio Tough Solar (WS220) uses a 6-mux backplane for its main display, everything except the dot matrix up top. Some notes here; if I were starting a new watch mod today, I'd almost certainly be playing with that one.
Honestly, it's a lot of the same things in the Pluto issue you linked to: 3 to 3.5 volts is what the SAM L22 supports, so that's where I wanted to be. The CA-53W / CA-506 watches would also fit this criterion and Travis Goodspeed uses this model as a donor watch for his GoodWatch. But with 35 pins on that LCD, you'd need to move up to a 100-pin chip (the SAM L22 N) to drive them all, and the only way to fit that in a watch case is by moving to a BGA package. As for price: I like that the watch itself is cheap enough that you can buy two or three of them: one for wearing, one for testing and one for hacking on. It would be challenging to do the same for a G-Shock, as those things can be pricey. Hope this helps! |
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wow the Hackaday talk is brillant wizard skills at play, didn't know anything about LCD nor anything that would go around reverse engineering the f91w display to accommodate something else, thank you for unleashing a little bit of that knowledge out there. |
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Thanks for the feedback! The Remoticon talk was great. Esp. the part on reverse engineering the Pinout. With theoretically compatible I was referring to the uCs capabilities, a pcb modification will most certainly be necessary. But to figure out if the uC is compatible I guess I have to figure out two things:
Both doable with a demo unit. Regarding the EL Backlight, do you have any idea how to pull this off? I am thinking external 5V boost circuit, assuming there is space for it. The pluto project uses 0.6mm thick PCBs due to space constrains, did you go that route as well? You mentioned a few uCs in your talk that include a LCD driver.
Did you stumble across any ARM alternatives after your talk, that can boost to 5V? |
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Ah ok yeah, those two things plus the LCD pin count are definitely the things to look for. Also note you can leave some segment pins floating (and therefore unaddressable) if you don’t have enough pins; depending on the segment map, that may be an acceptable tradeoff.
My instinct — and I’m just riffing here, I might be wrong — would be to measure what’s happening on those two EL pads with a multimeter, figure out the voltage and whether it’s DC or AC. Then use a power supply to feed that same voltage back to the EL backlight module, and if it lights, measure how much current it draws. That’ll tell you the requirements for your boost circuit.
Yep this one is all 0.6 mm PCBs. But I would measure the board in the watch you’re targeting; I forget which one it was, but one watch I took apart had an 0.8mm board. Getting this right is important because a lot of mechanical things like battery contacts and spring connectors depend on the board thickness matching up.
The deciding factor was its similarity to the SAM D21 that folks in my corner of the community know and love. I know how to work with SERCOMs and TC’s on the SAMD series, and the SAM L is similar enough that I feel right at home (which accelerates my development). If you’re familiar with ST’s chips, you may make a different choice.
I did not, but one thing you might consider is writing a simple PIC firmware that just uses that PIC16 as your LCD controller; then using a low pin count MCU like the SAM L21 E to control it over SPI. Extra part count is a headache, but if it’s a larger watch and a bigger circuit board you might just have room. |
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Indeed I am, thanks to ST's brilliant discovery kit marketing :) Just leaving this here in case you, or someone else needs it in the future~
The PCB Pinout-segment mapping for the A168WA LCD looks like this: |
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Just measured backlight on A168, with a battery it's boosting from around -0.4V to 5.33V, at 2KHz with a roughly 50% duty cycle. Same behavior with a fresh battery. |
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Very cool!
The display has 27 Pins, just like the display of the F-91W, I did not find a schematic for the F-91W, thus I don't know if they are compatible.
The seemingly identical design, plus the identical placement of the common pins, strongly hint to me that the A168 uses the same LCD glass as the F-91W. On a cursory check against my notes on [the F91W's segment map](https://joeycastillo.github.io/Sensor-Watch-Documentation/segmap.html), every segment I looked at matched up with your diagram.
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speaking of model compatibility, and having multiple watches for hacking, does anyone know if the F-91W clones are compatible with the original? importantly in terms of shape and LCD |
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It's highly unlikely that clones will work. Aside from shape, the important thing for this mod is the spacing of the LCD pads and the placement of the LCD common pins. This isn't something the clone manufacturers have any reason to clone precisely, and while only gotten my hands on one clone, its LCD pads are arranged differently. While the Sensor Watch board more or less fits physically, the display is not at all compatible. This mod will only work with an authentic Casio F-91W. |
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guess that will have to wait for a custom LCD one day 😉 I might try my luck anyway, I have an authentic, but I was seeing if I could avoid tearing it apart (again) |
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I've been wondering if the W218H-1A with the 3224 module will work with the sensor watch module? The only reason I'd like to swap the module into the W218H-1A vs the F91W is the 50M water resistance. Any ideas what kind of water resistance I can expect out of the F91W-1 case in real life practice? Thanks! |
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Firstly, I can't actually answer your questions, but there are reports on the internet of the F-91W being better than you'd expect in terms of water resistance (i.e. people reporting swimming and showers without issue). The other thing is, when I was looking for 593 module watches, this site said Casio used to make one which was rated to 50m: http://www.digital-watch.com/DWL/1work/casio-w-39 But when I was searching for ones that were currently made, I could only find: https://www.sensorwatch.net/docs/#need-to-buy-a-watch (none of these are 50m) |
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Thanks, appreciate the details, even if I'm still in search on the W218H-1A. I might just buy one and take it apart next to the F91W to see. |
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I suspect the LCD Is wired differently if nothing else. You could try putting the 593 module in that case (someone in Discord was doing that with a B640, which required more drastic hackery due to the button positions). |
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Found something very interesting and post it here, because of the discussion about the electroluminescence backlight: |
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Hi,
I hope it's ok to open this topic here?.
I am trying to figure out if this project would in theory be compatible with two other Casio models.
The two models I am specifically interested in are the A168 due to it's electroluminescence backlight, which i was planning to transplant into a A1000 case. Or the G-shock GMW-B5000.
Problem is, it is hard to figure out what kind of display (Backplane config) these models are using.
Due to this project https://github.com/carrotIndustries/pluto I know that the displays are a little finicky, apparently many of the casio watches use displays with 5 backplanes, which apparently is an issue for many uC's.
Based on the Datasheet Page 935, the SAML22 that your project is using also doesn't seem to natively support a 5 backplane config. The pluto project mentioned that running in 8backplane mode would severely hurt the display contrast. Any idea how bad a 6 backplane config would turn out to be?
https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/DataSheets/60001465A.pdf
What made you chose the F-91? The conversion cost seems kind of excessive, in relation to the watch price :D
/TM
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