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multiple Open Drain UART over long distance I have 9 microcontrollers  and I have connected the RX and TX lines of 8 of them in parallel. My configuration is in master-slave. The master microcontroller send data to one of the 8 RX lines but only one of them can respond at a time. The cable length is about 3 to 5 metres between each node.  I have two questions. My test was done with 2 slaves instead of 8. UART at 9600bps.  If I setup the TX lines of the slaves as Open Drain it works fine, but the signal doesn't have steep ramps. I thought this happens due to Pull-up resistors. And I also think that is going to be better with 8 slaves on the bus, right?  Why doesn't that topology work if the TX lines of the slaves are not Open Drain?  I managed to make it work by disabling the transmit of the UART in all of them except one, and it worked fine. I had two slaves, so I disabled the one and left the other. Also I noticed that the edges of the signal was sharper. Why are they sharper in that case?  Regarding resistors: The value of the resistors for both RX and TX lines are 2.7KΩ. However the Open Drain topology would parallel the internal pull-up resistors. According to the datasheet that resistor is about 20KΩ at minimum. So, using a 2.7KΩ in the output would give us a total resistance of 2.52KΩ (20+2.7)/9. And the Open Drain would make a voltage divider 2.52KΩ + 2.7KΩ (Schematic 2). Which means with 8 slaves and Open Drain topology the signal will not go lower than 1V which is the threshold of the low level. Is that correct?  Wouldn't it be better to disable all the internal pull up resistors and place two (let's say: 4.7KΩ) only at the master side?  Distance: What is the maximum baud rate for such distance? I'm a little worried about the signal integrity. The test was done with 9600bps but I didn't notice any significant difference in 4800bps. The distortion of the signal didn't have a difference.  Voltage values are 3.3V for the UART bus.  Schematic 1. (all resistors are 2.7KΩ)        &ndash; Schematic created using   Schematic 2. (U4, U5, U6, U7, and U8 are omitted for simplicity).          EDIT: Thank you all very much about your answers so far. I wanted to point out that this is a question about UART only. I am not looking for alternative solutions. I'm just trying to find some answers about the above implementation.  EDIT2: Thank you very much for your answers! I ended up modifying a little my schematic. I disabled the internal pullup resistors of the microcontrollers and I placed external ones at the master's board. Their value would be around 1 KOhm to 3 KOhm. I have to do some tests more to decide the final value. I also replaced all series resistors with 130 Ohm.   I tested 5 slaves over 20 metre cable (with pullup 3 KOhm and 130 Ohm series resistors) and it worked fine.   Would it be better to add open drain/open collector line drivers on every TX lines? From a previous question, we have that $\sqrt[3]{3} \notin \mathbb{Q}(\sqrt[4]{3})$, and I am assuming that we would need to use this to justify the answer to the question.   Would it be right to use some idea of a splitting field here? Or is it something to do with $\mathbb{Q}(\sqrt[3]{3}, \sqrt[4]{3})$ not containing a primitive 3rd root of unity?   This is a past exam paper question worth 8 marks, so it doesn't seem like it's a few lined answer, but I am a little stuck on where to go. How should we cope with 12 month old waking in the night? We are trying to get our 12 month olds sleep routine improved now that both of us will be returning to work.  We've been working on getting the settling routine sorted out each night, and haven't quite yet got to him falling asleep on his own, but he does now settle quickly at the end of the routine in our arms.  We will be moving to trying to get him to settle in his cot soon.  Once settled he will tend to do about 3-4 hours in his cot before waking screaming.  When cuddled he will settle down in about 10 minutes and can generally be put back in his cot.  However often he will wake several times.  Last night he went down at 8, woke at 10, woke at 12, woke at 1am.  Each time putting him back in his cot.   At that point we gave up and brought him into our bed where he slept through to 6am.  When waking up he is often on either all fours or standing in the cot whilst screaming.  The main problem is that he's no longer sleeping "solidly" and will often poke and prod his mum in his sleep, and she therefore doesn't get a great nights sleep.  And with us both back to work we both need our sleep as much as possible. How do I remove all loose edges? I have cut a hole in a plane, but I am left with some loose edges.  Is there an easy way to select and delete them all?  See this screenshot:    See this edges siting out with no face? Dual Canadian and British citizen - healthcare coverage in the UK? Math contest integer triplet problem: $x + y + z + xy + yz + xz = xyz − 1$ Is it true that smell is lost flavor? This is a maxim that I hear frequently, especially as a defense of cooking methods that don't produce a lot of aroma: if the aroma is in the air, it means it's left the food.  As an example, some people complain about the lack of aroma produced in sous vide cooking, to which the sous vide advocates retort that this is evidence that more flavor is in the food.  Likewise, I recently saw , where he went for a low-and-slow approach that produces little aroma: here, too, he claimed the flavor-retention defense to its lack of appeal. "Don't be disappointed, but my roasting technique doesn't flood your kitchen with good Sunday roast smells. This is a good thing, because smells are lost flavor" he said, while "SMELL = LOST FLAVOR" popped up on the screen.    I suppose it stands to reason, and that's the appeal of this explanation, but is it the truth? Does smelling a food necessarily imply that the final product will be less flavorful, and is it strictly because the aroma is escaping? How to understand intuitively the Stolz-Cesaro Theorem for sequences? Apparently,   $$ \sum_{n = 0}^\infty \frac{n}{2^n} $$  converges to 2. I'm trying to figure out why. I've tried viewing it as a geometric series, but it's not quite a geometric series since the numerator increases by 1 every term. Maximum Champion Growth size I was reading about Lulu (new champion) and saw this:     Wild Growth (Ultimate) - Lulu enlarges an ally, knocking enemies away   from them and granting them a large amount of bonus health. For the   next few seconds, that ally gains an aura that slows nearby enemies.   Then I start wondering: what is the max size that a champion reach ? Is there a Maximum size ?  Example: Cho'Gath's Feast +  +  + Wild Growth + Something that make champions grow in size. Cho'Gath will grow every time ? or it will stop at some point ? How do I get my C# program to sleep for 50 milliseconds?  This might seem an easy question, but I'm having a temporary brain failure moment! I don't have a minecraft folder. I've looked through forums and videos, followed all the steps. I just don't have one. I have windows 7, and I have "view hidden files" turned on. I have look in the roaming folder of my app data folder, with hidden files turned on. I want to find my folder so I can install a mod, could someone please tell me why my folder isn't showing up? How to find out if my system is i386 or x86_64 before installing Ubuntu? I am using Windows as of now and want to install Ubuntu. I want to find out if my system is i386 or x86_64? How do I do that? Why is "improve this question / answer" shown to anonymous users instead of "edit"? If I browse a site as an anonymous user, instead of "edit" I see: "improve this question / answer".        I don't get it, are anonymous users considered to be kinda dumb and don't understand "edit"?  Why to reword this action? How can I use only the external flash on slave mode without firing the built-in flash? I have a Canon 700D and YN-568EX ii external flash that I am using in slave mode. But whenever I try to fire the built-in flash pops up automatically and fires itself. Is there any option to use only external flash? How do I write this matrix as a product of elementary row matrices. \begin{pmatrix}3&amp;-1&amp;3\\ -2&amp;3&amp;2\\ 1&amp;-3&amp;1\end{pmatrix}  Any help would be greatly appreciated!  I have done this before with other matrices, yet this one is bringing me trouble. I have spent too long on this as I believe it should be easy and yet my answers are always wrong. What Do you do after you get the identity matrix?  What I am doing: So I first row reduce it to the identity matrix:   I first switch $R_1$ and $R_3$ Then $R_3-3R_1$ then $R_2+2R_1$ then $-1/3R_2$ then $R_3-8R_2$ then $R_2-2R_1$ then $3/32R_3$ then $R_1+3R_3$ and finally $R_2+4/3R_3$   I know there is many possible ways to get this too the identity matrix but this worked for me. I then apply all of the above steps to identity matrices and multiply them together to check my work but it never works out to be the original matrix so I am forced to believe something is wrong. As I understand, correct plural versions of passerby and attorney general become passersby and attorneys general.  But why?  With passerby, the the preposition "by" has been combined with the noun "passer" to become a one word noun "passerby".  So why shouldn't this be passerbys?  If I am an attorney general, and you are an attorney general, why are we not attorney generals?  As an American I have always heard it as attorneys general, however  suggests British English does use "attorney-generals" (as well as an interesting 2nd paragraph that further probes my question).  Are there hard rules to this topic?  Or merely generally accepted practices based on locale? I have a point $(X,Y)$ on an elliptical curve $E(a,b)$ where $a=-3$ and $B$ is a large number that is in hexadecimal from -51BD. To compress this point oficially in a program, we know that every $X$ on the curve has two $Y$'s, one even and one odd. Therefore, we only need to store whether the corresponding $Y$ point we are storing is even or odd. So to store the point $(X,Y)$ now, we shift $X$ ridding of its most significant bit and add $1$ if the $Y$ point is odd. Therefore, one can think of the compressed point being $2 \cdot X+B$ ($B$ is the bit we added to tell if $Y$ was odd or even) since the multiplication by $2$ is implied because of the shift. I understand this completely. It's recovering the original point that has me confused.  Since a point on the curve is given by the equation $y^2=x^3+ax+b$, we can find square roots officially in $\mathrm{GF}(p)$. The following from my spec is what confuses me.  If $p$ is prime and congruent to $3$ mod $4$, one of its square roots is $z^{(p+1)/4} \bmod p$ and the other is $p-z^{(p+1)/4} \bmod p$. How would I solve this? What is $z$?  For example, I know how to extract the $x$ point so let's say I simplify the right side of the equation to be $7$ and $p$ is $11$. Would I be trying to solve for the square root that's equal to $7$ mod $11$? Why does SharePoint always prompt me to download SharePoint Designer when I already have it installed? For example, if I click Edit page -&gt; Edit in SharePoint Designer from within my SharePoint site, I'm always presented with a dialog prompting me to download Designer.  I already have Designer installed.  Seems like it should a.) launch it for me, or b.) at least stop prompting me to  download it.  UPDATE: Turns out this stemmed back to the 64-bit IE compatibility issue that was causing me grief here: Selecting faces on object from UV editor window I can't see this as an option so is there a way to select faces or islands and have them show up as selected faces on the object in 3D view.  In programs such as maya it is possible to work from either view and makes selection and mapping a little more user friendly.  I suspect it isn't possible in Blender but welcome your feed back.  Edited as flag as already answered, although the question was not asked in the other post in a way that showed in my search.  I was looking for face and island selection to show in both views. The other asked about unselected vertices this obviously did not appear in the results.