rstring: A Resistor Divider Calculator Written in Rust

I wrote rstring as an excercise to learn Rust, a pretty modern programming language.

Compilation instructions are at the bottom of this page.

First Thoughts on Rust

The Rust programming language first appeared around 2010 (today is mid 2016). The language prioritizes memory safety, especially in concurrency, and it mixes together quite a few modern programming paradigms: functional, imperative, and object oriented. Rust aims to provide all of this with little run-time cost by using a clever compiler and strict language rules.

Coming from C programming, I think Rust feels like C but with a lot more rules. With Rust, dumb programming mistakes involving memory and types are banned at compile-time. For example, Rust has a sophisticated data ownership system that restricts the mutability (ability to change the value) of data in memory. As a result of these rules, a lot of time is spent fighting the compiler, rather than debugging the code at run-time. You'll still need to be careful of things like your array indices' range, but you can rely on the compiler to slap you over and over again when you try to be clever with pointers and dynamic memory.

In addition to the language, Rust also has the Cargo package manager and build environment. It allows the programmer to quickly get libraries from an online repository and manage local versions. It also has an interface for doing both unit tests, full system verification, and documentation generation. It is basically a one button solution.

I'm quite hopeful about Rust.

Program Description

rstring is a command line program that finds the closest preferred value (E-series) resistors to produce "tap" voltages from a resistor divider, given the total resistance and the source voltage applied across the divider.

If no taps are given, the program simply finds the resistor that is closest to the given total resistance.

Essentially, you give it voltages and it gives you a string of resistors, hence the name rstring

Features

Arbirary number of tap voltages
Resistor options: E6, E12, E24, E48, E96, E192, or ideal resistance
Cool ASCII graphic of a resistor string
Outputs Formats: Human Readable, CSV, or SPICE sub-circuit
Error and current analysis

Examples

Usage

$ rstring
Usage: rstring [Opt. E Series] [Opt. Format] [Source Voltage] [Total Resistance]
  [Tap Voltages...]

  E Series options (defaults to E12 series if not given): 
    -e6, -e12, -e24, -e48, -e96, -e192, -ideal

  Format options (defaults to human readable if not given):
    -csv, -spice

  Description:
    Finds the closest preferred value resistors to produce "tap" voltages from a
    resistor divider, given the total resistance and the source voltage applied
    across the divider.

    If no taps are given, the program simply finds the resistor that is closest to
    the given total resistance.

Typical Use

$ rstring -e12 10 54321 1 1.5 5.4 2.6 3.9 8.1


 | 10 V 
 |
[ ]  1.0000e4 Ohms 
 |---- Tap 1: 8.1785e0 V (Ideal: 8.1 V, Error: 0.97%)
 |
[ ]  1.5000e4 Ohms 
 |---- Tap 2: 5.4463e0 V (Ideal: 5.4 V, Error: 0.86%)
 |
[ ]  6.8000e3 Ohms 
 |---- Tap 3: 4.2077e0 V (Ideal: 3.9 V, Error: 7.89%)
 |
[ ]  6.8000e3 Ohms 
 |---- Tap 4: 2.9690e0 V (Ideal: 2.6 V, Error: 14.19%)
 |
[ ]  6.8000e3 Ohms 
 |---- Tap 5: 1.7304e0 V (Ideal: 1.5 V, Error: 15.36%)
 |
[ ]  2.7000e3 Ohms 
 |---- Tap 6: 1.2386e0 V (Ideal: 1 V, Error: 23.86%)
 |
[ ]  6.8000e3 Ohms 
 |
 | 0 V

Current Consumption:    0.000182 Amperes
Total Resistance:   5.4900e4 Ohms (Ideal 5.4321e4 Ohms, Error: 1.07%)

SPICE Output

$ rstring -e12 -spice 10 54321 1 1.5 5.4 2.6 3.9 8.1
* Resistor Divider String
* Input Voltage: 10 V
* Total Resistance: 54900 Ohms

.SUBCKT RDIV VPOS VNEG TAP1 TAP2 TAP3 TAP4 TAP5 TAP6 
R1 VPOS TAP1 10000
R2 TAP1 TAP2 15000
R3 TAP2 TAP3 6800
R4 TAP3 TAP4 6800
R5 TAP4 TAP5 6800
R6 TAP5 TAP6 2700
R7 TAP6 VNEG 6800
.ENDS

CSV Output

$ rstring -e12 -csv 10 54321 1 1.5 5.4 2.6 3.9 8.1 | column -t -s,
SourceVoltage    10
Current          0.00018214936

Item              Value          Ideal   Error%
TotalResistance  54900          54321   0.010658861
Tap1             8.178507       8.1     0.9692157
R1               10000                  
Tap2             5.446266       5.4     0.8567792
R2               15000                  
Tap3             4.2076507      3.9     7.888476
R3               6800                   
Tap4             2.9690351      2.6     14.193665
R4               6800                   
Tap5             1.7304195      1.5     15.361301
R5               6800                   
Tap6             1.2386162      1       23.861622
R6               2700

Compiling rstring

The rstring was written in Rust with the Cargo environment. You'll need to install Cargo or at least the rustc compiler.

With Cargo

At the top level directory, run

cargo build --release

and the executable will be built as target/release/rstring

With rustc

In the src directory, run

rustc main.rs -o rstring

and the executable will be built as rstring