Allow custom numbering scheme in PadArray and QFN scripts

[rnd2]

Custom pin numbers for the pad array can be passed to PadArray
as a list through the keyword argument pad_numbers.
This bypasses the increment functionality.

Additonally, add the ability to define custom pin numbers per side on a QFN
package, as some packages use a non-standard numbering scheme.

This is needed for KiCad/kicad-footprints#1553 and it seems that there is also related issues (#323, #280)

As an example, here is the definition from the pull request mentioned above using the changes I suggest. Notice the EP_pin_number for the exposed pad and pad_numbers_{top,right,left,bottom}

Texas_X2SON-4-1EP_1.1x1.4mm_P0.5mm_EP0.8x0.6mm:
  device_type: 'X2SON'
  library: Package_SON
  manufacturer: 'Texas'
  #part_number: 'mpn'
  size_source: 'http://www.ti.com/lit/ds/symlink/drv5032.pdf#page=28'
  ipc_class: 'qfn' #'qfn' | 'qfn_pull_back'
  #ipc_density: 'least' #overwrite global value for this device. (if used, pad values are closer to TI's suggested fp)

  body_size_x:
    minimum: 1.05
    maximum: 1.15
  body_size_y:
    minimum: 1.35
    maximum: 1.45
  overall_height:
    maximum: 0.4

  lead_width:
    minimum: 0.17
    maximum: 0.27
  lead_len:
    minimum: 0.15
    maximum: 0.25

  EP_size_x:
    nominal: 0.8
    tolerance: 0.05
  EP_size_y:
    nominal: 0.6
    tolerance: 0.05
  # EP_paste_coverage: 0.65
  EP_num_paste_pads: 1 #[2, 2]
  EP_pin_number: 5

  pitch: 0.5
  num_pins_x: 2
  num_pins_y: 0
  #include_suffix_in_3dpath: 'False'
  #include_pad_size: 'fp_name_only' # 'both' | 'none' (default)

  pad_numbers_top: [1, 4] # left to right
  #pad_numbers_right: [5, 6] # top to bottom
  pad_numbers_bottom: [2, 3] # left to right
  #pad_numbers_left: [8, 7] # top to bottom

  thermal_vias:
    count: 1
    drill: 0.2
    # min_annular_ring: 0.15
    paste_via_clearance: 0.1
    EP_num_paste_pads: 1 # [2, 2]
    EP_paste_coverage: 0.75
    grid: [1, 1]
    paste_avoid_via: False

And the resulting footprint:

Edit: Add related issue

[codeclimate]

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[tolot27]

I recommend checking for duplicates and in case of (consecutive) numbers for gaps. If such occurs, a warning is the minimum.

[rnd2]

I recommend checking for duplicates and in case of (consecutive) numbers for gaps. If such occurs, a warning is the minimum.

That sounds like a good idea. Probably a warning is the best approach, as there might be some packages which reuse pin numbers.

[poeschlr]

Using an array to get the pin numbers into the array function feels a bit non pythonic. My guess is that it must work with generator functions. I will get back to you when i am not as tired as today. (If it takes more than a few weeks then ping me.)

[rnd2]

Use this as an entry point for custom pin-number generator functions

[rnd2]

When you say generator functions I believe you don't just mean to use a python generator (i.e. yield), but actually define pin-number generator functions for the most common uses cases and use the total pin number as the function's input.

And I guess these functions can be plugged to callable(self.increment) (see comment).

Does this sound right?

[rnd2]

With the latest changes, the definiton for DMR4000 will be:

Texas_X2SON-4-1EP_1.1x1.4mm_P0.5mm_EP0.8x0.6mm:
  device_type: 'X2SON'
  library: Package_SON
  manufacturer: 'Texas'
  #part_number: 'mpn'
  size_source: 'http://www.ti.com/lit/ds/symlink/drv5032.pdf#page=28'
  ipc_class: 'qfn' #'qfn' | 'qfn_pull_back'
  #ipc_density: 'least' #overwrite global value for this device. (if used, pad values are closer to TI's suggested fp)

  body_size_x:
    minimum: 1.05
    maximum: 1.15
  body_size_y:
    minimum: 1.35
    maximum: 1.45
  overall_height:
    maximum: 0.4

  lead_width:
    minimum: 0.17
    maximum: 0.27
  lead_len:
    minimum: 0.15
    maximum: 0.25

  EP_size_x:
    nominal: 0.8
    tolerance: 0.05
  EP_size_y:
    nominal: 0.6
    tolerance: 0.05
  # EP_paste_coverage: 0.65
  EP_num_paste_pads: 1 #[2, 2]
  EP_pin_number: 5

  pitch: 0.5
  num_pins_x: 2
  num_pins_y: 0
  #include_suffix_in_3dpath: 'False'
  #include_pad_size: 'fp_name_only' # 'both' | 'none' (default)

###### Custom pad numbering #####
  pad_numbers:
    generator: 'ccw_dual'
    axis: 'x'
###############################

  thermal_vias:
    count: 1
    drill: 0.2
    # min_annular_ring: 0.15
    paste_via_clearance: 0.1
    EP_num_paste_pads: 1 # [2, 2]
    EP_paste_coverage: 0.75
    grid: [1, 1]
    paste_avoid_via: False

[poeschlr]

@pointhi this looks good to me have you any input?

[pointhi]

@poeschlr I'm okay with this

[rnd2]

@pointhi When you merge this I will make a PR for the definition neeeded for KiCad/kicad-footprints#1553.

[poeschlr]

As @pointhi gave the ok i assume i am ok with merging this. Thanks