ckanext-scheming is a CKAN extension for customizing dataset, group and organization metadata forms, validation rules and display templates.

With ckanext-scheming 3.0 CKAN dataset metadata forms may now be split across multiple pages using start_form_page.

Example ckanext-scheming schema:

- start_form_page:
    title: Detailed Info
    description:
      These fields improve search and give users important links

  field_name: tag_string
  label: Tags

Each start_form_page block marks a field at the beginning of a new page of fields. All following fields without a new start_form_page block will appear on the same page. This lets us maintain compatibility with existing schemas and makes it easy to reassign pages over time without affecting how metadata appears in the API.

We crank up the bit rate for a widescreen character LCD video experience using our new 512K flash.

Based on the encoder we developed for our Bad Apple on 32K EEPROM video but with our clock running 25x faster, we test the limits of our LCD character display.

In this video we replace our clock’s 4011 CMOS Quad-NAND gate IC with a TTL equivalent and discuss compatibility between different logic families.

We connect an HD44780-powered LCD character display to the circuit and play a simple text animation from the program ROM.

We build a larger address register and use it to test an SST39SF040 512k flash chip.

This is part two of a two-part series. Read part one here.

In this post we use Python to encode the full Bad Apple video (3m39s) into 32 kilobytes. Our playback hardware has no CPU so our video “compression” is limited to the features of our HD44780-powered LCD display.

We create an illusion of a full bitmap display by carefully juggling 8 CGRAM characters across the 8 x 4 video area and lean on LCD display persistence.

This is part one of a two-part series. Read part two here.

This post covers how we interface a 32K EEPROM, a clock and an address register to a 20 x 4 LCD character display module and use it to play a video. We “decompress” the video by expanding our 8-bit data stream to 9 bits for playback in hardware. There is no CPU or microcontroller involved.

We complete our clock module by adding a halt signal and test it with our address register. Now our (future) programs won’t have to run forever.

We add a reset circuit to our clock module that resets our address register to “0” on power-on and when a button is pressed.

We add three more 74LS163’s to our counter to make a 16-bit address register for our homebrew CPU project.

We connect our clock circuit to a 74LS163 synchronous binary counter and see how to count, reset and load values into the counter.

We add a potentiometer and a single-step button to our clock circuit.

In this video we create a clock circuit with a 555 timer in astable mode, and use it to blink a green LED.

This video introduces the first milestone for our homebrew CPU project.

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• Excalidraw

This youtube tutorial covers interfacing with an LCD2004 20x4 LCD Character Display module with an HD44780 controller using only switches and simple components on a breadboard.

ckanext-scheming 2.1 now support Datasets with repeating subfields and repeating text fields. Repeating subfieds support custom snippets and validation just like regular fields.

This work is inspired by the excellent ckanext-composite extension and replaces ckanext-repeating repeating_text fields.

You must be using CKAN 2.8 or later and a custom IPackageController plugin to index datasets with repeating subfields.

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