open-source-silicon.dev

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I have created the <https://github.com/StefanSchippers/xschem_sky130|xschem_sky130> repository on github that contains a first set of symbols to be used with the sky130 pdk. Right now there are symbols for the 1.8V, and higher voltage P and N mos, resistors, diodes and the pnp bipolar transistor All these symbols have been simulated with ngspice (a simple dc sweep) . The xschem_sky130 contains a xschemrc file, running xschem from this directory will set the correct search paths. The top level schematic (loaded automatically on xschem startup) contains 6 subcircuit testbenches, for testing diodes, bipolar pnp, resistor, Nfet, Pfet and finally a ring oscillator for testing the process speed (1.8V fet). Any feedback welcome :slightly_smiling_face:  <@U018459959C> <@U01698PQ13R> <@U016EM8L91B>

Very nice! I'll update my tutorial to use them

Thank you! i am interested to know if you find problems of any kind. :+1:

<https://github.com/StefanSchippers/xschem_sky130/blob/main/xschemrc#L20> - should this be `append XSCHEM_LIBRARY_PATH :${XSCHEM_SHAREDIR}/xschem_library/devices`  maybe?

It seems that when I run with that `XSCHEM_LIBRARY_PATH` I get errors about not finding symbols like `vsource`

but if I add /devices/ in the end it works fine

in the submitted repo and test cases i am referencing symbols in schematic as 'devices/ipin.sym' instead of just 'ipin.sym'. See this <https://xschem.sourceforge.io/stefan/xschem_man/tutorial_xschem_libraries.html|tutorial>

for big designs, typically VLSI/ASIC, i use one level indirection to better avoid name clashes

on the other end pcb hobbysts / small circuits designers will blame me for this, so either way is possible

the less specific the XSCHEM_LIBRARY_PATH the more specific the component references in the schematic. The end goal si to avoid absolute paths in schematic, that is evil.

for VLSI the 'one directory specification' symbol references is almost mandatory. for example , when creatin the diode models for sky130, the cell name is specified to be diode.sym, that already clashes with the generic diode.sym supplied in devices.

I will include a step in the tutorial where the user will configure the xschemrc and explain why

It seems reasonable to me that you have to set up what components you want to use

very good!!. for issues or misbehaviours let me know, i like to hear about other user's experiences

yes, using only a component name is too generic, at the end there is a good chance to pick up the wrong one. Xschem searches the search path in the order it is given and picks the first match