Dimming an RGB lightstrip using a Tiny2040 (Pi Pico)

 This is just a simple experimental project to try out Pimoroni's Tiny2040 for the first time.

In order to dim LEDs we have to use PWM; change the duty cycle of a square wave. The 2040 chip handles this and so this program is really simple, it just sets up PWM on one pin and handles two inputs, one for brighter, one for dimmer. 

The harder part was controlling 12v LED strip using a 3.3v output. I've used a small transistor to amplify to 5V and then a mosfet to step that up to 12v. A 7805 gives us a 5v supply to power the microcontroller and to use in the amplification circuit.

It would be possible to generate three square waves with independent duty cycles, and thus have smooth colour changing with the RGB LEDs.

PicoTerm, terminal application for Raspberry Pi Pico, supported escape codes and user-definable characters

PicoTerm is an application for the Pi Pico which provides a serial terminal with VGA output and USB keyboard input.

It was developed for the RC2014 and therefore is configured for that computer; eg 115,200 baud and the RC2014 logo at startup. However, if you'd like a custom version, please get in touch.

The Pico has resources that allow for a 640*480 output with a character mode, or 320x240 with full  32,000 colour.

I've recently added support for uploading user-defined character data. I've made this page in order to document the escape codes currently supported, along with information about the new UD character functionality.

Here is the list of supported escape codes, followed by the information about defining characters.

• \ESC[?25l | Cursor invisible
• \ESC[?25h | Cursor visible
• \ESC[H | Move to 0-0
• \ESC[s | Save the cursor position
• \ESC[u | Move cursor to previously saved position
• \ESC[-Row-;-Col-H | Move to -Row-,-Col-
• \ESC[0K | Clear from cursor to the end of the line
• \ESC[1K | Clear from the beginning of the current line to the cursor
• \ESC[2K | Clear the whole line
• \ESC[2J | Clear the screen and move the cursor to 0-0
• \ESC[-n-A | Move the cursor up -n- lines
• \ESC[-n-B | Move the cursor down -n- lines
• \ESC[-n-C | Move the cursor forward -n- characters
• \ESC[-n-D | Move the cursor backward -n- characters
• \ESC[0m | normal text (should also set foreground & background colours to normal)
• \ESC[7m | reverse text
• \ESC[0J | clear screen from cursor
• \ESC[1J | clear screen to cursor
• \ESC[3J | same as \ESC[2J
• \ESC[nS | scroll whole page up by n rows (default 1 if n missing)

40 col colour only: (sequence is ignored, no effect in 80 col b/w)

• \ESC[38;5-n-m | Set foreground colour to -n- (0-255)
• \ESC[48;5;-n-m | Set background colour to -n- (0-255)
• \ESC[38;2;r;g;bm | Set foreground colour to r/g/b (values 0-255, scaled by picoterm to 0-31 to give 32,000 colours)
• \ESC[48;2;r;g;bm | Set background colour to r/g/b (values 0-255, scaled by picoterm to 0-31 to give 32,000 colours)

80-col textmode version only: (from version 1.1)

• \ESC[1L | Insert line at cursor position, scrolling down from the cursor's row
• \ESC[1M | Delete line at cursor position, scrolling up to the cursor's row

User-definable characters

C/PM (which is widely used on the RC2014) uses 7-bit ascii characters, which means that there are 128 characters (128-255 inclusive) unused and available for defining by the user. In the case of the colourmode  version of Picoterm, the character data is simply stored as pixel data (foreground colour/background colour, 8 bytes per character) and drawn to the screen when needed, which means that the 'reverse graphics' doesn't rely on those reverse characters being defined, and therefore works on the default fixed characters and any that you define.

Note that this functionality is present in picoterm colour v0.2.0 onwards, which is available here.

• \ESC[?-n-U | followed by 8 bytes, which will be inserted into the user-defined character space for character n (n can be 128-255 inclusive)

When displaying custom characters, the current foreground and background colours apply, these being reversed if reversed graphics is on.

Here is the simple basic program used in the screenshot above to display pacman: (yes, it's possible to use a loop to define the four characters, but beware of MS Basic's tendency to add a space when using STR$. It's expanded here for readability.)

10 PRINT CHR$(27);"[?128U";

20 FOR C=1TO8

30 READ A

40 PRINT CHR$(A);

50 NEXT C

60 PRINT CHR$(27);"[?129U";

70 FOR C=1TO8

80 READ A

90 PRINT CHR$(A);

100 NEXT C

110 PRINT CHR$(27);"[?130U";

120 FOR C=1TO8

130 READ A

140 PRINT CHR$(A);

150 NEXT C

160 PRINT CHR$(27);"[?131U";

170 FOR C=1TO8

180 READ A

190 PRINT CHR$(A);

200 NEXT C

205 PRINT CHR$(27);"[38;5;11m";

210 PRINT CHR$(128);CHR$(129)

220 PRINT CHR$(130);CHR$(131)

230 END

1000 DATA 15,63,127,127,255,252,224,252

1010 DATA 0,192, 224,224,128,0,0,0

1020 DATA 255,127,127,63,15,0,0,0 

1030 DATA 128,224,224,192,0,0,0,0

Inconsistent results with Integrity

 Running the existing release alongside a potential new release is a great sanity check to make sure that any new changes haven't had any undesirable effects on the results.

Today this happened (the new Integrity Pro and existing release are showing different results):

It was a head scratcher and I had to sort the sitemap tables and carefully compare them to find the differences.

The reason is that I'd put some A/B testing in place, there are a bunch of pages with differences and A or B in the querystring. It's in an area of the site I'd normally ignore for reasons, but didn't today.

Therefore, the list of pages may feature both the A version and the B version (because the url of the page is the unique key for Integrity). So those pages may be duplicated in the results, or maybe not, and that's a matter of chance. 

Ignoring querystrings fixed the problem, and now gives consistent results every time. (Querystrings aren't used for any other reason on this site, so it's fine to ignore them).

Electronic Dice with the Pi Pico

This was my first project with the Pi Pico. It's a 'Hello World' for hardware/software.

The real reason for two buttons is that I already had the box drilled and fitted with the two buttons for a different project. It made sense to switch the power using an arcade button, because it's automatically switched off when you let go of it. The second button grounds the 'run' of the Pico, which means that it performs the shuffle and display once more. In reality, just the one power button would do, because letting go of that and pressing it again does the same thing as the 'run again' button.

I wrote the software in Micropython because this was my introduction to the Pico. More recent projects use C which suits me much better.

* That should probably be electronic die, because one die is shuffled and displayed. The pico has enough pins to shuffle and display 3 dice, and probably many more with a bit of logic to decode the binary numbers 0-6 (3 GPIO pins) to 7 LEDs.

'Not allowed to load local resource' error with Safari

 If, after archiving a site in 'browsable' / 'processed' form using WebArch or Website Watchman, parts of the page aren't visible, it may be because of Safari's security restrictions.

If a page uses a js file and that file has been properly saved locally, the browser may still not allow access to that file.  Open up your browser's console and check:

Here you can see my browser isn't allowing access to mmenudom.js, even though that file exists in the same folder as the index.html file. 

The answer is simple, from the Developer menu, select 'Disable Local File Restrictions'. 

I should add that this restriction exists for a reason, and that you shouldn't leave it disabled permanently.

Terminal software for the Raspberry Pi Pico

 I am very proud to have been involved in this hardware / software project with Spencer, creator of the RC2014.

The Pi Pico is a powerful microcontroller, it runs at 133 Mhz by default but can be overclocked to 400Mhz. It has two cores and eight state machines. The state machines have their own assembly language and can independently manage i/o or dma tasks.

It is capable of buffering and generating a video signal, VGA or DVI. Using the TinyUSB library it's capable of receiving USB input.

With these features, it's the perfect candidate for this task. With a few supporting components and the software/firmware installed, it's acting as a serial terminal with USB keyboard input and VGA output. 

The RC2014 is a retro-style computer running a Z80 at up to 7.372Mhz. It does require you to use some kind of terminal for input and output. Usually this is a terminal program running on a modern computer and that's where this new module comes in. It allows the computer to be used standalone, as seen here with CP/M running on the RC2014. It communicates with the computer using UART serial via two of the Pico's GPIO pins and the Rx and Tx lines on the RC2014 bus. It receives keyboard input via the micro USB socket on the Pico (with an OTG adaptor. NB TinyUSB on the pico seems to work with some keyboards and not others.)

The project required custom software to be written for the Pico in C. 

The video output is taken care of by libraries, although the example code certainly did take a while to understand. That part of Textmode PicoTerm largely draws on the text mode example code. 

The USB handling uses TinyUSB. The Pico must act as a host (with the keyboard connected via an OTG adaptor). 

That leaves the terminal functionality. You need to maintain a buffer to store the characters (because the video functionality makes callbacks, requesting the data for each scanline as it's generated). Scrolling is an important  feature of a terminal, so I created a structure to store the character codes for each row of characters, and an array of pointers to those rows. So scrolling is a matter of shuffling 30 pointers rather than 2400 characters. 

One of the Pico's cores can handle the scanline generation for the video while the other listens for characters sent from the computer and from the keyboard, buffers and handles those. [update - with the textmode Picoterm, polling was fine and works without dropped characters. With the newer colourmode PicoTerm, because of the increased load of putting characters on the screen, it was necessary to implement interrupts on Rx to receive and buffer each incoming character].

As well as just feeding characters to the screen and scrolling when necessary, it's also important to parse and handle certain escape sequences.  These codes can position the cursor on the screen or change the attributes (eg reverse characters). The full list of sequences that we've implemented so far are here on the module's documentation page.

• RC2014 Pi Pico VGA Terminal

Submitting page changes to Bing Webmaster Tools / IndexNow

IndexNow was recently brought to my attention. It seems that Bing are trying to gain some ground on Google by promoting IndexNow for fast indexing as well as a 'one-stop-shop' - submit once to Bing and 'participating search engines' (which I assume won't ever include Google). Read more

With a well-established and open 'XML sitemap' schema, naturally Microsoft have decided to invent their own xml format and submission protocol. To be fair it's very simple, it is no more than a list of urls and doesn't include the last modified and priority fields, which may not have had any effect anyway. 

To submit your xml to Bing can't be done by web upload or ftp, but by http POST request. I guess the idea is that content management systems can submit page(s) as soon as they're edited or created, which is a terrific idea. 

It's very easy for Scrutiny / Integrity to generate this XML and make the POST request. It's a simpler variation on what these apps do already with sitemap XML files. 

This functionality will appear on Scrutiny 10.4.6 (Scrutiny isn't always the first to get a new feature, it happens that the user who has been helping me with this with is a Scrutiny user). Here's the relevant part of the updated manual:

Exporting and submitting XML for Bing Webmaster Tools / IndexNow

IndexNow is designed to allow faster indexing of your page updates by multiple search engines. 

From version 10.4.6, Scrutiny can generate the xml in the correct format, split into batches of 500 if necessary, and submit them to Bing for IndexNow.

In Preferences > Sitemap, the options for saving locally and ftp'ing have been altered slightly to read 'transfer' rather than ftp, and these options apply to both traditional XML Sitemaps and the Bing Webmaster Tools XML format.

Bing Webmaster Tools require a http POST request, which contains an API key. To use this feature you'll need to enter your key in this box in Preferences. Here's where to find your key:

As before, you'll need to scan your site and go to Sitemap results. Examine the list to make sure that it contains the pages that you expect. This time the last modified and priority are irrelevant (The Bing format only allows for a list of urls).

Find "Bing Webmaster XML" in the Export button above the Sitemap table, or use File > Export > Bing Webmaster XML.

"Leveraging tools like Scrutiny and Bing's IndexNow can significantly improve a website's visibility by ensuring that search engines quickly recognize and index important updates. Staying ahead in SEO means not just optimizing content but also optimizing how it's discovered." - Maria Harutyunyan, CEO of professional SEO company Loopex Digital