new pwm2 module

[fikin]

Fixes #2667, follow-up to #2669

• This PR is for the dev branch rather than for master.
• This PR is compliant with the other contributing guidelines as well (if not, please describe why).
• I have thoroughly tested my contribution.
• The code changes are reflected in the documentation at docs/*.

an implementation capable of running up to few x100kHz with varying periods, sub-Hz and fraction of frequencies, support for all gpio pins and compatible with CPU160MHz.

[TerryE]

See comments inline. These are mostly Lua and NodeMCU Lua style issues. I leave it to @devsaurus and @pjsg to comment on the realtime aspects.

[TerryE]

Conditional operator considered unhealthy 😉

[fikin]

i'm not catching this up, what do you mean?

[jmd13391]

@pjsg "We had to add support for multiple users of the hw_timer as people didn't read the documentation closely enough and would complain that using module A and module B at the same time would not work."

If I recall correctly ( #2494 #2497 ), multiple users functionality was added to allow gpio.pulse and pwm modules to work at the same time (this simultaneous functionality is critical to several of my projects). During the course of you providing this functionality, you discovered and corrected at least one bug and added clarification to the gpio.pulse docs. IMO, this had little to nothing to do with "not reading the documentation closely enough".

Losing the multi-user hardware timer functionality (especially with gpio.pulse / pwm) would be detrimental to several of my ESP8266 based products already out in the field.

[fikin]

@jmd13391 : i think no one is thinking of loosing current capabilities to share timer1 between modules. not me at least.
it is more about offering ability to either share it or reserve it exclusively for given module.

[TerryE]

This has failed Travis as a consequence of #2742. Have a look at the other modules, e.g. app/modules/file.c for how to declare ROTables.

[HHHartmann]

Just to be sure, this Module is not supposed to replace the PWM Module, right?
Maybe it would be a good idea then to rename it to something like PWM-fast or some other fitting name to distinguish it from the original PWM Module.
Also a common section to PWM and PWM2 documentation to help the user decide which one to pick would make sense.
Sorry for being so late ...

[fikin]

@HHHartmann : i've added a small section in pwm2 doc about comparison with pwm. let me know how useful you're finding it.

[fikin]

@TerryE : apparently i'm not getting how to return values from c to lua. what i am missing in get_timer_data?

[TerryE]

apparently i'm not getting how to return values from c to lua. what i am missing in get_timer_data?

The return value to any C method called from the Lua VM is not a status; it's a return argument count. Typically this matches the number of responses that your routine has pushed onto the Lua stack, but the VM will ignore / push extra nils if needed. So lpwm2_get_timer_data() should return 3 and so on.

[fikin]

ok, now to module is more or less ready.

[marcelstoer]

Nit pick: you're missing newlines at the end of most files. GitHub reports this if you look at https://github.com/nodemcu/nodemcu-firmware/pull/2747/files

[fikin]

@marcelstoer : ok, i've added missing new lines.
btw how documentation is tested?

[galjonsfigur]

Documentation can be tested using mkdocs. You can install it using pip (for examplepip3 install --user mkdocs) then just use mkdocs serve command in project directory. But to show up in module list you will have to add link to pwm2 documentation in mkdocs.yml file and it should work.

[fikin]

@galjonsfigur : thanks, i've opted using "docker run -i --rm -v $(pwd):/docs -p 8000:8000 melopt/mkdocs serve" ...

[marcelstoer]

Documentation was correctly published at https://nodemcu.readthedocs.io/en/latest/modules/pwm2/ and the module is available in the cloud builder (given you select the dev branch).