connecting to laser TTL

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poesel
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04 Jan 2025 11:26 #318044 by poesel

connecting to laser TTL was created by poesel

Hi,

just to make sure I understood that correctly.
I have a 7i96s and want to connect a laser module which uses a TTL signal to control it. When I connect it like shown below, the M67 command will control the intensity, right? Or do I need to configure something to make that work?

Thanks!

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tommylight
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04 Jan 2025 13:45 #318061 by tommylight

Replied by tommylight on topic connecting to laser TTL

No, analog output does not work for TTL inputs:
analog output = changing voltage from 0 to 5V
PWM = Pulse Width Modulation = pulses with changing duration, so 0 or +5V
-
The correct way would be to flash PWM firmware to Mesa 7i96S included in the downloads from Mesa website (specification tab on the 7i96S page), this will replace the 5'th stepgen with PWM.
If you do need all 5 stepgens, then a cheap BOB connected to Mesa IDC26 header will also work, but i do not know if that also needs flashing or can be used with software PWM.

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poesel
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04 Jan 2025 15:02 #318081 by poesel

Replied by poesel on topic connecting to laser TTL

Well, I know what TTL & PWM means. The problem is, that TTL (in this context) only means 5V while PWM is just pulses with no indication to voltage or frequency.

The manual of the Atomstack M100 just says 5V TTL. I googled, but did not find any good indication if they meant 5V analog or PWM. Usually (YMMV) more devices work with analog than PWM, so I went that road.

If, from your experience, TTL in this context means PWM, I'll happily take that advice. If you remember, you explained to me yesterday how to flash the second PWM output. So this has already been done.

I'll look up in the manual how that needs to be wired and post it here.

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tommylight
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04 Jan 2025 16:01 #318091 by tommylight

Replied by tommylight on topic connecting to laser TTL

poesel wrote:
If, from your experience, TTL in this context means PWM,

Yes it does. In this case it means 5V PWM, see below:
The naming TTL has remained from logic IC's back when there were two types of them, the TTL ones (Transistor-Transistor-Logic) and CMOS ( C.... Metal Oxide Semiconductors, damn it cant recall what C stands for),
TTL are 5V powered with +-5% tolerance, and if i recall correctly, "logic 0" was anything under 0.8V and "logic 1" was anything over 2.4V
CMOS were powered by 3V to 9V or more, i think, and "logic 0" was under 33% of the supply voltage and "logic 1" was everything above 66% of the supply voltage.
A bit fuzzy on details, been over 40 years since i used those daily.

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poesel
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04 Jan 2025 17:35 #318108 by poesel

Replied by poesel on topic connecting to laser TTL

Ok, so I have flashed the card with 7i96s_2pwmd which changes STEP4 to a PWM output. Then connect the STEP4- output on the mesa card with TTL on the laser controller and the same with GND on both sides.
HAL config as per this discussion:
forum.linuxcnc.org/27-driver-boards/5480...and-wiring-for-laser

That correct? Thanks.

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connecting to laser TTL

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