TTL to differential converter (STEP / DIR / ENABLE)

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29 May 2026 06:24 #346724 by Asymmetrisch
Hello everyone,are there any breakout board to convert TTL signals (3.3 V to 5 V) into differential signals for motor controllers?
I found a converter that was specifically made for that, but unfortunately it’s not available in Germany:
www.cnc4pc.com/shop/c72-c72-differential..._hygKwfclSAuFTXaBSfB
 Thanks and best regards,
Gerhard

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29 May 2026 11:07 #346728 by andrax
du brauchst ein TTL zu RS422 Konverter.
Da gibt es jede Menge bei Amazon

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29 May 2026 12:25 #346733 by Asymmetrisch
Replied by Asymmetrisch on topic TTL to differential converter (STEP / DIR / ENABLE)
Ah ok, vielen lieben Dank!
Das sind dann die Konverter mit dem MAX490, und hier dann nur TXD, Y und Z (Senden) anschließen, richtig?

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29 May 2026 12:39 #346734 by andrax
Jupp,
txd = transmid Data
rxd = receive data

du willst ja nur Senden, also txd
Board ist eigentlich egal, z.b. das hier:
Amazon

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29 May 2026 13:35 #346735 by Asymmetrisch
Replied by Asymmetrisch on topic TTL to differential converter (STEP / DIR / ENABLE)
Gibt es so eine Lösung evtl. auch gleich mit mehreren Kanälen?
Da kommen ja doch einige Module zusammen bei 3 oder 4 Achsen...

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29 May 2026 17:39 - 29 May 2026 21:02 #346742 by PCW
The conversion interface parts depend on the signal levels needed.

For RS-422 (going into a line receiver on the drive ) where 3V signals into a load are OK,
any RS422 driver will work (say 26LS31 equivalent for 4 channels/chip)

If you wish to drive optocoupled drive inputs that expect 5V signals, you would need
a driver with 5V outputs. AFAIK the only 4 channel RS-422 drivers that do this are
the ISL32174,ISL34172 and MAX3042 (The MAX parts are expensive)

Another option for 5V signals is to use a combination of ACT driver chips with inverting
and non-inverting  outputs, say a 74ACT540 and a 74ACT541.
Last edit: 29 May 2026 21:02 by PCW.
The following user(s) said Thank You: andrax

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29 May 2026 18:30 #346744 by andrax
Also ich hab mal geschaut.
Standartmäßig gibt es meistens max 3 Kanal für die typischen ABZ Encoder.
Gegenfrage: was hast du vor, evtl. gibt es eine andere Lösung?

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30 May 2026 05:22 #346761 by Asymmetrisch
Replied by Asymmetrisch on topic TTL to differential converter (STEP / DIR / ENABLE)
I have several motor controllers that are driven by differential signals (CLK, #CLK, DIR, #DIR) – the inputs (5V, Ri = 120 Ohm) are not optically isolated. At first glance, it seems that controlling it with my Mesa 7i76EU works perfectly.

For testing purposes, I'd like to use the parallel port or possibly a RP2040 – in addition, I have a "Benezan Mini Breakout Board" left over from a previous setup that I could use.
It would be great if there were a solution for this.

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30 May 2026 15:27 #346773 by PCW
For testing purposes with just a parallel port, you could use 2 pins for one signal and invert one in hal
to get differential signals.

As long as the output bits come from the same physical port (say PP pins 2..9),  and the hal addf
order and thread is correct. the outputs will change simultaneously.

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03 Jun 2026 17:18 #346876 by Asymmetrisch
Replied by Asymmetrisch on topic TTL to differential converter (STEP / DIR / ENABLE)
Would this change in the hal for parallel port pin 2/3 be correct?

loadrt not count=1
addf not.0 base-thread

net xstep stepgen.0.step => parport.0.pin-02-out
net xstep => not.0.in
net xstep-neg not.0.out => parport.0.pin-03-out

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