Add README for Agilent34405A MATLAB Driver

Added documentation for Agilent34405A MATLAB Instrument Driver, including requirements, installation instructions, usage examples, supported measurement modes, configuration utilities, properties, and notes.

README.md

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+# Agilent34405A — MATLAB Instrument Driver
+
+A MATLAB class for controlling the **Agilent 34405A bench multimeter** over USB/VISA. Provides a clean, object-oriented interface for all major measurement modes, configuration, and instrument lifecycle management.
+
+---
+
+## Requirements
+
+- MATLAB with the **Instrument Control Toolbox**
+- **NI-VISA** driver installed
+- `Agilent34405AStates` enumeration class (companion file)
+
+---
+
+## Installation
+
+1. Clone or download this repository.
+2. Add the folder to your MATLAB path:
+   ```matlab
+   addpath('/path/to/Agilent34405A');
+   ```
+3. Ensure the multimeter is connected via USB and recognized by NI-VISA.
+
+---
+
+## Quick Start
+
+```matlab
+% Instantiate — automatically finds the instrument via USB
+dmm = Agilent34405A();
+
+% Read DC voltage
+v = dmm.readDCV();
+
+% Read AC current
+i = dmm.readACI();
+
+% Read temperature
+t = dmm.readTemp();
+
+% Clean up when done
+dmm.deInit();
+```
+
+---
+
+## Supported Measurement Modes
+
+| Method | Description |
+|---|---|
+| `readDCV()` | DC Voltage |
+| `readACV()` | AC Voltage |
+| `readDCI()` | DC Current |
+| `readACI()` | AC Current |
+| `readTemp()` | Temperature |
+| `read2WRes()` | 2-Wire Resistance |
+| `readCont()` | Continuity |
+| `readDiode()` | Diode Test |
+| `readCapacitance()` | Capacitance |
+| `readFrequency()` | Frequency |
+| `readPeriod()` | Period |
+| `scan()` | Scan mode |
+
+All measurement methods automatically switch the instrument to the correct mode if it isn't already configured.
+
+---
+
+## Configuration & Utilities
+
+### Set Measurement Scale
+```matlab
+% obj.setScale(state_string, [resolution, range])
+dmm.setScale('VOLT:DC', [0.001, 10]);
+```
+
+### Trigger & Sample Settings
+```matlab
+dmm.sampleCount  = 20;   % Number of samples (default: 10)
+dmm.triggerCount = 4;    % Trigger count (default: 1)
+
+dmm.setSampleCount();    % Apply sample count to instrument
+dmm.setTriggerCount();   % Apply trigger count to instrument
+dmm.setTriggerSource('BUS');  % Set trigger source
+```
+
+### Send Arbitrary SCPI Command
+```matlab
+% Automatically reads response if command contains '?'
+response = dmm.sendCommand('VOLT:DC:RANG?');
+dmm.sendCommand('DISP:TEXT "Hello"');
+```
+
+### Other Utilities
+
+```matlab
+dmm.getConfig()       % Query current instrument configuration
+dmm.selfTest()        % Run built-in self-test and print result
+dmm.reset()           % Send *RST to instrument
+dmm.setBeep(true)     % Enable/disable beeper
+dmm.setLocal()        % Return front-panel control to user
+dmm.approxTime(state) % Benchmark acquisition time for a given state
+dmm.deInit()          % Cleanly close and release the VISA connection
+```
+
+---
+
+## Properties
+
+| Property | Default | Description |
+|---|---|---|
+| `visaAddress` | *(auto-detected)* | USB/VISA address of the instrument |
+| `state` | `DCV` | Current measurement mode |
+| `numSamples` | `512` | Internal sample buffer size |
+| `sampleCount` | `10` | Samples per trigger sent to instrument |
+| `triggerCount` | `8` | Number of triggers |
+
+---
+
+## Notes
+
+- The constructor **automatically detects** the instrument address using `instrhwinfo('visa','ni')` — no manual address configuration needed.
+- The beeper is **silenced on startup** by default.
+- `deInit()` should always be called when finished to cleanly release the VISA resource.
+
+---
+
+## License
+
+MIT License — see [LICENSE](LICENSE) for details.