Tilt #1

July 8, 2025

I want to add a tilt feature. Not because it's needed, but because I like to practice my mojo with a limit. I've got a bunch of tilt mechanisms, but they all need refurbishing, and I've had enough of that for a while; so I says to myself...

Why not build an electronic tilt mechanism?

As usual, this was a stupid idea - not only was it not easy, it was not fun, and it's not even done.

To start with I needed an accelerometer. I selected the ADXL345 chip, on a board often labelled GY-291 (mine isn't).

Here's a picture of it with a JST 8 pin connector attached instead of the usual headers.

❗ So the first part of the cautionary tale is voltage. Some vendors will advertise 5 volt operation, but that's a little tricky as they often mean 5 volt supply, not 5 volt inputs. Some units have voltage-shifting devices fitted to them so they can work on 3.3 or 5 volts, but most don't. Mine will run from 5 but needs 3.3 inputs (which is pretty common) so I shall use a 3V3 microcontroller to save all that level-changing nonsense.

Moving on, we sort out Chip Select and I2C mode, so we can talk to the chip - not so hard, except it never seemed to work.

I hooked the accelerometer up to this beast, loaded some popular code, and got errors galore™️ and an occasional something-that-looked-promising. As it happens, the something-that-looked-promisings were just more errors.

I loaded some I2C diagnostic software, and the ESP32 could find the ADXL345 right enough, it just couldn't talk to it. Many hours of fiddling did not help. I went to bed.

The next day I had a look in my microcontroller box and found that while I had plenty of microcontrollers, I didn't want to solder them up because I'd not be able to reuse them easily. I decided to test a Raspberry Pi 2040 chip on a RP2040-Zero board, even though the software I was using was not tested on it. Why? They are cheap, and small, and fast, and have enough I/O for the job.

❗ So what pins does it use for I2C communication? The doco shows that the chip could use any of 23 pins to do the job. Much searching found a comment in a forum. https://forum.arduino.cc/t/issues-with-i2c-communication-on-waveshare-rp2040-zero/1235882 so I thought I'd give that a go rather than trawling through the library.

A quick wave of the soldering iron and...

Connections

JST8	Colour	ADXL345	Description of signal/use	RP2040	2040	Location
JST	JST	Board	ADXL345	Board	Chip	(USB up)

1	Black	GND	Ground	GND	GND	2 from top LHS
2	Red	VCC	Supply Voltage 3-5V	3V3	3V3	3 from top LHS
3	White	CS	Chip Select	3V3	3V3	3 from top LHS
4	Yellow	INT1	Interrupt 1 Output	nc
5	Orange	INT2	Interrupt 2 Output	nc
6	Green	SD0	Serial Data Output (SPI 4-Wire)	-	-
			or I2C Address Select	GND	GND	2 from top LHS
7	Blue	SDA	Serial Data I2C	4	GP4	5 from top RHS
			or Serial Data Input (SPI 4-WIRE)	-	-
			or Serial Data Input and Output (SPI 3-Wire)	-	-
8	Violet	SCL	Serial Communications Clock	5	GP5	6 from top RHS

⭐Tested and worked first time!

❗ Counterfeit electronics from China strikes again! That ESP32 is more like an ESP0.32; probably a marginal chip that was binned, "reclaimed" by an entrepreneur, and sold to me as working. Lot of that going on. I buy lots of microcontrolers from China, including the working RP2040-Zero.

You pays your money and you takes your chances.

What Library to use?

I found these libraries the good old search engine way:

Library	Contributor	URL
ADXL345_WE.h	Wolfgang Ewald	wolles-elektronikkiste.de/en/adxl345-the-universal-accelerometer-part-1
		github.com/wollewald/ADXL345_WE
Adafruit_ADXL345_U.h	Adafruit	github.com/adafruit/Adafruit_ADXL345
ADXL345.h	Seeed Studio	www.seeedstudio.com
Luis Llamas	Luis Llamas	www.luisllamas.es/en/arduino-adxl345-accelerometer/

Examination

I had a gander at them all, poked around the header files, and a look at available doco, and did some actual testing:

Library	Contributor	Testing	Can Use
ADXL345_WE.h	Wolfgang Ewald	Works, has many examples inc. interrupt code	yes
Adafruit_ADXL345_U.h	Adafruit	Works, very abstracted	yes
ADXL345.h	Seeed Studio	No data returned	⚠️no
Luis Llamas	Luis Llamas	No data returned	⚠️no

⚠️ My testing is not your testing - my modules, chips, libraries all impact on my testing. If it does not work for me, it may still be perfect for you.

Pros and Cons of the two working (for me) libraries

Library	Pro	Con
Wolfgang Ewald	Many examples
	Interrupt examples
	Closer to hardware
		Not as commonly used

Adafruit	Abstracted
	Common
		Abstracted
		Mysterious
		1 example

You might note that Abstracted is a pro and a con. It's great for ease of code, but not for fault-finding.

I decided to go with Ewald Wolfgang's library, and see where that takes me.

Update

@Homepin, and @Railways gave me some great feedback, and I this is my reasoning for not just fitting a standard tilt bob.

I have some mechanical tilt mechanisms. I don't want to clean up the mechanical tilt mechanisms. Maybe in a year or so I'll be able to face them... I'm all brasso'ed out.
There's this thing that happens where harmonic motion increases the tilt bob's swing, so that several gentle nudges result in a tilt, I want to eliminate that "feature".
My old Fish Tales liked to tilt multiple times because the bob-hook did a shimmy, a figure 8 instead of swinging back and forward. I want to remove that "feature" as well.
It's self-levelling - so I don't need to adjust it if I change the angle of the machine. I don't know if that's actually a thing, but hey, it sounds good.
It's small and does the job of the bob, the rolling ball-in-a-cage thing (I bet that's got a name), and the slams - so I don't need to fit any of them, although I don't need them, it's nice to have.
Someone wasn't thinking and mounted something on the playfield that would bump into where the bob should go...
Price, my <<sophisticates electronics>> is running at $6

If the cabinet had a tilt mech fitted, would I bother - no

If I had a clean and tidy tilt mech would I bother - no