100k resistor on MS1 pin of A4988 Carrier
Posted by FBITuco
|
100k resistor on MS1 pin of A4988 Carrier April 29, 2014 08:13AM |
Registered: 10 years ago Posts: 166 |
|
Re: 100k resistor on MS1 pin of A4988 Carrier April 29, 2014 04:25PM |
Registered: 10 years ago Posts: 869 |
From the A4988 Data Sheet:
As to being useless, I'd have to defer to the electrical engineers at Allegro in their design decision on why MS1 and MS3 need a 100k pull down resistor and MS2 needs a 50k one. But based on their design decision, my guess is it IS useful and that those resistors are just pulling the line low to ensure they are low unless the jumpers are enabled to set them high.
Quote
Microstep Select (MSx). The microstep resolution is set by
the voltage on logic inputs MSx, as shown in table 1. The MS1 and
MS3 pins have a 100 kΩ pull-down resistance, and the MS2 pin
has a 50 kΩ pull-down resistance.
As to being useless, I'd have to defer to the electrical engineers at Allegro in their design decision on why MS1 and MS3 need a 100k pull down resistor and MS2 needs a 50k one. But based on their design decision, my guess is it IS useful and that those resistors are just pulling the line low to ensure they are low unless the jumpers are enabled to set them high.
|
Re: 100k resistor on MS1 pin of A4988 Carrier April 30, 2014 01:27AM |
Registered: 10 years ago Posts: 166 |
I don't think we are speaking about same thing :-).
Look at Sango scheme: [reprap.org]
There is additional external 100k pull-down resistor R3 on MS1 pin.
I know that internal resistors are there to pulling line down... It can't "fly" in the air. Try left unconnected input of ADC and You will see...
So... Why additional pull-down?
Look at Sango scheme: [reprap.org]
There is additional external 100k pull-down resistor R3 on MS1 pin.
I know that internal resistors are there to pulling line down... It can't "fly" in the air. Try left unconnected input of ADC and You will see...
So... Why additional pull-down?
|
Re: 100k resistor on MS1 pin of A4988 Carrier April 30, 2014 08:22AM |
Registered: 13 years ago Posts: 7,616 |
Quote
FBITuco
I'm wondering why every circuit diagram (Of repRap electronics) has 100k resistor to ground on MS1 pin.
Early Pololu stepper drivers (A4983 based) didn't have such a pulldown onboard, so the big electronics board had to provide one. A4983 based ones are still in use and the pulldown doesn't conflict with newer ones, so it's still kept.
Gen7 electronics took a slightly different approach, fixing MS1 to high and saving a few parts at the loss of quarter and full step microstepping modes.
| Generation 7 Electronics | Teacup Firmware | RepRap DIY |
|
Re: 100k resistor on MS1 pin of A4988 Carrier April 30, 2014 09:38AM |
Registered: 10 years ago Posts: 166 |
Quote
Traumflug
Early Pololu stepper drivers (A4983 based) didn't have such a pulldown onboard, so the big electronics board had to provide one. A4983 based ones are still in use and the pulldown doesn't conflict with newer ones, so it's still kept.
Gen7 electronics took a slightly different approach, fixing MS1 to high and saving a few parts at the loss of quarter and full step microstepping modes.
There was somethink before A4988? That is new for me :-).
I can see it now in [www.pololu.com]. Pulldown on MS1 is missing... Thx for answer :-).
Edited 1 time(s). Last edit at 04/30/2014 09:39AM by FBITuco.
Sorry, only registered users may post in this forum.