Optocoupler CTR, SRAM reset restore, voltage-limited current source, macOS paste

[esaruoho]

Summary

Rebased onto v3-dev (replaces #223 which targeted master).

• Adds adjustable CTR (current transfer ratio) for OptocouplerElm
• Adds "Restore Contents on Reset" option for SRAMElm (snapshots initial state)
• Adds voltage-limited current source (FLAG_VOLTAGE_LIMIT on CurrentElm)
• Fixes macOS Cmd+V paste in Electron app

Fixes #150, #184, #149, #138.

Changes from master version

• Extended v3-dev's dumpXml()/undumpXml() in CurrentElm and SRAMElm to serialize new fields
• SRAMElm integrated with v3-dev's parseContentsString() helper

Test plan

• Place Optocoupler → edit → verify CTR adjustment works
• Place SRAM → load data → enable Restore on Reset → reset → verify data restored
• Place current source → enable voltage limiting → verify current reduces at voltage limit
• In Electron on macOS → Cmd+V → verify paste works

🤖 Generated with Claude Code

[esaruoho]

@pfalstad any takes on this?

[pfalstad]

I tried to do the limited current source thing once and got constant convergence failures. Looks like your version has the same issue. Try opening all the switches. Also I wouldn't have a separate checkbox for the voltage limiting. I would just use a default of 0 meaning unlimited.

<cir f="1" ts="0.000005" ic="10.20027730826997" cb="50" pb="50" vr="5" mts="5e-11">
  <w x="112 32 208 32" f="2"/>
  <w x="208 32 304 32"/>
  <w x="304 32 400 32"/>
  <s x="208 32 208 112" p="1"/>
  <s x="304 32 304 112"/>
  <r x="208 112 208 176" r="100"/>
  <r x="304 112 304 176" r="400"/>
  <r x="400 112 400 176" r="4000"/>
  <w x="208 176 304 176"/>
  <w x="304 176 400 176"/>
  <w x="304 208 304 176"/>
  <w x="304 208 400 208"/>
  <w x="304 208 208 208"/>
  <s x="304 208 304 288"/>
  <r x="208 288 208 352" r="600"/>
  <r x="304 288 304 352" r="200"/>
  <s x="400 208 400 352"/>
  <w x="112 352 208 352"/>
  <w x="208 352 304 352"/>
  <w x="304 352 400 352"/>
  <i x="112 352 112 32" f="1" cu="0.01" mv="5"/>
  <g x="112 352 112 384"/>
  <w x="400 32 400 112"/>
  <w x="208 208 208 288"/>
  <o en="20" sp="32" f="x3" p="0">
    <p v="0" sc="20"/>
    <p v="3" sc="0.05"/>
  </o>
</cir>

[pfalstad]

the sram thing is good

[pfalstad]

The optocoupler thing looks good. I would maybe just rename "CTR (%)" to "CTR Scale" because it doesn't look like the CTR is exactly 100... At least in my test case it wasn't.

[pfalstad]

the mac thing is good

[MatNieuw]

An optocoupler's CTR depends also on the current. There is usually a peak CTR between 5 and 20 mA diode drive current, and the peak varies per type. In the datasheets it is given as a percentage (like 80%), or absolute value like 0.8 . I think being able to specify a peak CTR at a certain diode current would be nice. As an example, the CTR specs from a CYN80N.