Hacking di2 shifters with a SRAM BlipBox

So, there was a story a few months ago about TdF mechanics making di2 satellite shifters work with AXS shifters.

But is it possible to get Shimano di2 shifters to work with a SRAM BlipBox, and thereby a SRAM derailleur?

Why? Well, I like to tinker. I like Shimano’s lever shape and brakes better than SRAM’s. But I also want to be able to run a mullet.

Any thoughts?

I reckon if you gutted them so it’s only got the switches it would probably work since it’s just bounce switches. Although it could be an expensive experiment.

I guess if you’ve got a lever to sacrifice you could try it out, then if it works horay, if not you just get some SRAM levers.

2 Likes

I think it is unlikely to work. The “sprint” buttons are simple switches which can be wired directly to the control unit. The Di2 shifter controls use a proprietary communication protocol which is encoded in firmware.

I found this out to my great cost when I tried to integrate the Di2 wiring into a frame by running copper tape between layers of wood and using it to connect the various DI2 bits. The shifter firmware refused to interface with the changed wiring: I am guessing it didn’t receive the correct handshake to enable the protocol. The rear derailleur, however, was OK with copper tape in the chainstay connecting it to the interface box. Go figure.

I ended up having to rebuild the frame with standard internal wiring (except the chainstay).

1 Like

Sounds like the signal was distorted too much by the copper tape- probably an impedance issue. Some of the tech talk was mentioning that the newer, narrower etube cables were higher capability (bandwidth? power? I don’t know), so the copper tape chainstay run might not work either.

I do not think it was an impedance issue, the tape lay approximates a stripline which is a standard layout for RF signals on PCBs. I calculated the characteristic impedance of the tape lay and it was fairly close to 50 ohms which is, I believe, the characteristic impedance of the E-tube wiring. Of course I could be wrong.

In the end I threw the whole thing into the too hard basket or more accurately the too-much-effort-for-bugger-all-gain basket.

There’s more to impedance than just resistance. I figure the tape makes a decent capacitor, so you get an RC filter that distorts the edges of the waveforms. There might also be reflections due to that imaginary part of the impedance.

ETA: But I haven’t had to deal with signals for a while, so who knows?

I said characteristic impedance which takes the capacitance and inductance into account.

That goes to show, I know just enough to sound stupid :slight_smile:

1 Like

No harm no foul. I work with this stuff on a regular basis: I design and build specialist wine industry equipment including the PCBs for the controls.

1 Like

Thanks a lot to you both!

As an aside, you can get cheap switches on Amazon or AliExpress and wire them onto di2 cables to make cheap blip/climbing switches. A mate has done it, going to give it a try myself soon.