Personally, I’ve never bothered. I know some people use zflasher and I’m not sure about that, but avrdude does a full chip erase before flashing, so the factory reset default config is loaded on first boot anyway.
That’s what Hank does for the D4S with an RGB switch. The single channel driver wasn’t designed for one, just a BUTTON_LED (I assume it doesn’t have space on the pads to solder two wires to each R/G/B header?), so he uses the dual channel driver, and connects all 4 LEDs to the FET channel, then uses the K9.3 firmware to enable 100% FET on that channel, but it does mean that 3H on the stock firmware switches to the nonexistent second channel.
@Jeffgoldblum 
Now TK has updated the K9.3 build target, it’s possible to make a version where 3H doesn’t switch if you were interested. Unfortunately the MCU layout isn’t the same (and the dual channel has enable pins per-channel while IIRC the normal linear+FET doesn’t, only the boost for single channel) so the single channel D4S firmware doesn’t work on it.
That’s weird, mine has it so both channels make the emitters light up. I guess hank does it differently sometimes because it doesn’t usually matter?
It doesn’t seem like the normal driver even has the pad for the switch backlight, mine is the single-color and it came with a dual channel driver.
Maybe Hank is cycling out of the stock of old D4Sv2 drivers and starting to use a revised version? It might be a good idea to ask before putting together a build, but so far one with only CH1 and the ramp of KR4-FET would be a safe choice.
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D4K triple channel version.
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Looks really exciting, will it be possible to buy it with one of the small channels as UV with a small reflector and filter like K9.3 and D2?
Optic might need to be drilled out (but I’m sure most people would be ok with doing that themselves if it’s not possible for you)
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Nice! Linear or boost? Is there a FET on the 2 LED channel?
No, it’s three regulated channels.
I have an early prototype here, but there was an issue so the driver got revised again to fix it. Now we’re working out the remaining details. New prototype incoming soon, I think? Things go a lot faster when code compile / test cycles happen in minutes, instead of going back and forth between time zones.
I’m hoping to do some fun stuff with a RGB version… probably red on 2 LEDs since red needs more power to reach the same brightness, then green and blue are pretty bright on their own.
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More work for ToyKeeper 
You need a vacation
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I think the D4K 3 channel firmware is about ready, if you want it with white LEDs, flood, throw, warm, cool, red, or most other combinations. It works much like the 2 channel version, but with extra channel modes available to cover more hardware configurations.
For example, here’s a config I think might work well:
- ch1: Two W1 LEDs for throw
- ch2: 519A 2700K (warm white)
- ch3: 519A 5700K (cool white)
- optic: 10622 (medium), maybe with some DC-Fix over the warm and cool LEDs to blend them better … or 10623 (frosted) with the W1 parts polished for more throw
- channel modes: 1 (throw) and 5 (adjustable white)
Another config which seems nice:
- ch1: Two 519A 5700K dedomed LEDs (~4000K actual)
- ch2: SST-20 deep red
- ch3: W2 blue
- optic: 10623 (frosted) or 10622 (medium, expect square color beams)
- channel modes: 1 (white), 2 (red), and 3 (blue)
- tactical mode then gives high, low, and red/blue police flasher by default
I don’t recommend using the 10621 spot optic in this light. The default is 10623 (flood), but the 10622 (medium) could work sometimes too.
…
But for a RGB version in particular, there is quite a bit more work to do. I have many things to add for that. It will probably use its own special firmware, and I’m guessing it might have a different product page too. It adds a lot of features for light painters, including an entire new mode group dedicated to user-configurable color patterns. A traffic wand style attachment is recommended, if there are any that fit, because the color modes are designed to be waved around and make trails in the air. I also hope to blend all 3 channels as close to white as possible, so it can function as a normal flashlight when desired.
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Hi Hank, are there any plans to update the current 12V 2A/6V 4A boost drivers? Using the same MP3431/3432 converter as your current boost drivers its possible to bump up the power to 12V 3.5A/6V 7A like in this reddit post with a D4SV2 with thefreemans boost driver: https://www.reddit.com/r/flashlight/comments/14zjsip/new_driver_day_underpowered_stock_d4sv2_12v_2a/
Also are there any plans for a buck driver for the single 3V emitter lights like the D1/D1K/K1/KR1. Convoy has new 5A and 8A buck drivers in a 17mm size, for your 22+ mm drivers it should fit easily, maybe even dual channel buck. The new triple channel D4K is neat but me and I think a lot of others are more interested in new more efficient drivers for your current lineup
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Also this KR1 with RGB aux in the reflector is really cool, is this something that could be offered in the future?
https://www.reddit.com/r/flashlight/comments/15q2die/noctigon_kr1_with_xpl_hi_4000k_and_rgb_aux/
i was getting ready to order a d4v2 and then saw the triple channel option of the d4k and have it be a channel switching
so would this work?
ch1 w1
ch2 519a 2700k
ch3 red for night so it doesn’t kill your normal vision at night
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Imagine M64 with three channels of switched-mode efficiency 
Now that the firmware floodgates have opened.. I’d probably have myself a high CRI tint ramp and W1s for business.
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I can’t see this information elsewhere, I’m sure I’m not looking hard enough but I’ve given up.
Will it just be tint switching initially, or will there be some amount of mixing? If so, all three or just two channel mixing?
And is it safe to assume that for an 2R, G, B light will the issues you describe likely just be a firmware change or could there be a hardware component?
I’m sorely tempted to order it now, just for messing abouts sake, but if it’s just channel switching - or a functional RGB light Anduril light with different components could be forthcoming - I may hold off.
Either way, sounds like a labour of love on the firmware side…thanks for everything you do 
Hi Hank, are there any plans to update the current 12V 2A/6V 4A boost drivers?
This so much … for those of us using lights for work / utility this is one of the most important things. And the D4SV2 is almost a perfect utility light - I hope it stays otherwise unchanged with upgraded driver only.
Other improvements I would like to see to the driver
- t1616 (factory temperature calibration)
- better dynamic range (lower lows)
- better positive terminal conical springs (the current post + cylindrical spring setup has damaged too many of my batteries). More leniency here is required, maybe the battery tube also needs to be 1-2mm longer.
Efficient drivers are the foundation. Everything else should be built on that.
EDIT: An improved D4SV2 (better driver, optional 21700 tube) would probably be an instant hit and clobber the SC700, which even after years is unmatched in efficiency.
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This was on my mind as well!
Order in. So many choices…
The D4K 3-channel firmware currently has these channel modes:
- Channel 1 only (main 2 LEDs)
- Channel 2 only (LED 3)
- Channel 3 only (LED 4)
- All 3 channels in equal amounts
- Adjustable blend of LEDs 3 and 4
- HSV style blend of all 3 (ramp up/down for brightness, ramp sideways to change color)
But these can be changed, and there will probably be improvements over time. So I’d recommend getting a flashing adapter.
RGB hardware is available now, but RGB firmware is still in progress.
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Yeah the D4SV2 is my favorite Hank light, its so darn ergonomic and I like the extra throw of the ledil optic vs the smaller carclo ones.
If Hank just put thefreemans boost driver into production it would be perfect. it has the newer t1616, super low moonlight mode, and room for a better spring. It looks like if you moved the RPP FET on thefreemans driver a bit you could even fit Hanks super low resistance BeCu springs that he uses in the linear drivers (https://intl-outdoor.com/gold-plated-beryllium-copper-spring-5-pcs.html)
The small thin springs used in the dual channel and boost drivers dont give me much confidence: https://www.reddit.com/r/Hanklights/comments/v71g9t/kr1_fc40_driver_spring_collapsed/
I changed the one in my D4SV2 with one of these springs for peace of mind: https://www.mtnelectronics.com/index.php?route=product/product&path=25_81&product_id=972
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