MMA8451 clone accelerometer query

[fiddylamar-svg]

Hey there :)

I've ordered an actual MMA8451 breakout board, but I've also got a clone as seen in the eBay link:

https://www.ebay.co.uk/itm/235972939165

I tried cabling the clone up to a Pico in the same way you would the actual MMA8451, and it didn't work.

I'm new to the whole Pico thing but if someone can tell me why the clone didn't work that would help my curiosity while I wait for the real board to come in.

Here is the boot and error log from my previous attempts:

2025/08/06 18:08:19 Info: Flash JEDEC ID recognized as Winbond W25Q16JV-IQ/JQ, capacity 2097152 bytes
2025/08/06 18:08:19 Info: SFDP basic parameters table found, capacity entry found [4:7]{ ff ff ff 00 }, 2097152 bytes
2025/08/06 18:08:19 Info: Flash file system mounted; 131072 bytes allocated to 2 files
2025/08/06 18:08:19 Debug: File "config.json" opened for read, 32561 us
2025/08/06 18:08:19 Config: Config file loaded OK; parsed JSON memory usage: 5,328 bytes
2025/08/06 18:08:19 Info: I2C0 bus reset OK, 0 clocks sent
2025/08/06 18:08:19 Config: I2C0 configured on SDA=GP20, SCL=GP21; speed: 400000; DMA channels: TX 0, RX 1
2025/08/06 18:08:19 Error: MMA8451Q: WHO_AM_I read request failed
2025/08/06 18:08:19 Error: MMA8451Q: Error reading CTRL_REG1 (setting STANDBY mode)
2025/08/06 18:08:19 Error: MMA8451Q: CTRL_REG1 write failed
2025/08/06 18:08:19 Error: MMA8451Q: CTRL_REG2 write failed
2025/08/06 18:08:19 Error: MMA8451Q: CTRL_REG3 write failed
2025/08/06 18:08:19 Error: MMA8451Q: CTRL_REG4 write failed
2025/08/06 18:08:19 Error: MMA8451Q: CTRL_REG5 write failed
2025/08/06 18:08:19 Error: MMA8451Q: XYZ_DATA_CFG write failed
2025/08/06 18:08:19 Error: MMA8451Q: Error reading CTRL_REG1 (setting ACTIVE mode)
2025/08/06 18:08:19 Error: MMA8451Q device initialization failed; I2C0 address 0x1D, interrupt GP0, dynamic range +/- 2g
2025/08/06 18:08:19 Config: Open Pinball Device HID configured
2025/08/06 18:08:19 Config: USB CDC console enabled, output buffer size 8192, history size 256
2025/08/06 18:08:19 Info: Flash struct 'mma8451q.acc' not found (flash storage status code -1); using defaults
2025/08/06 18:08:19 Config: Nudge input configured on MMA8451Q; nudge x = device +X, y = +Y, z = +Z
2025/08/06 18:08:19 Info: Kb LED 01

Thanks for checking my query out, best wishes to you :)

[mjrgh]

If you've already double-checked the wiring, and you're sure that everything's right, you probably just have a bad part. Do you have any other equipment that can test an I2C device independently, such as a Bus Pirate board? That would let check for sure if it's the accelerometer chip that's the problem.

[fiddylamar-svg]

Thanks for the reply, I do believe it was wired correctly but I don't mind trying again :) I'll look into a Bus Pirate board and obviously try the official breakout when it arrives.

I'll try again, and I might upload my config. though it is essentially copy and pasted from the GitHub accelerometer page and edited as instructed, I'm sure I could have got it wrong somehow.

[fiddylamar-svg]

Hello again!

I received the actual accelerometer today. I soldered the headers and connected it up- still not working but at least the log says that the pico recognizes the board.

After booting up, the nudge tab doesn't show any readings whatsoever. I have tested the gpio pins on the pico, they all work.

2025/08/08 12:56:30 Info: Flash JEDEC ID recognized as Winbond W25Q16JV-IQ/JQ, capacity 2097152 bytes
2025/08/08 12:56:30 Info: SFDP basic parameters table found, capacity entry found [4:7]{ ff ff ff 00 }, 2097152 bytes
2025/08/08 12:56:30 Info: Flash file system mounted; 131072 bytes allocated to 2 files
2025/08/08 12:56:30 Debug: File "config.json" opened for read, 32570 us
2025/08/08 12:56:30 Config: Config file loaded OK; parsed JSON memory usage: 5,328 bytes
2025/08/08 12:56:30 Info: I2C0 bus reset OK, 0 clocks sent
2025/08/08 12:56:30 Config: I2C0 configured on SDA=GP20, SCL=GP21; speed: 400000; DMA channels: TX 0, RX 1
2025/08/08 12:56:30 Info: MMA8451Q: WHO_AM_I (reg 0x0F)=0x1A (OK)
2025/08/08 12:56:30 Config: MMA8451Q device initialization OK; I2C0 address 0x1D, interrupt GP0, dynamic range +/- 2g
2025/08/08 12:56:30 Config: Open Pinball Device HID configured
2025/08/08 12:56:30 Config: USB CDC console enabled, output buffer size 8192, history size 256
2025/08/08 12:56:30 Info: Flash struct 'mma8451q.acc' not found (flash storage status code -1); using defaults
2025/08/08 12:56:30 Config: Nudge input configured on MMA8451Q; nudge x = device +X, y = +Y, z = +Z
2025/08/08 12:56:30 Info: Kb LED 01

I've attached my config json and a picture of my wiring just in case. It's possible that my soldering might be bad but hey ... I have a spare MMA8451Q just in case.

Thank you for your support with this, the project (a briefcase digital pinball) will be massively improved with accelerometer nudge :)

[fiddylamar-svg]

myconfig.json

Here's the json, hopefully!

[mjrgh]

The log looks good as far as the I2C connection goes. Try firing up a console connection (with a terminal program like PuTTY, connecting to the COM port shown on the overview page of the Config Tool) and type mma8451q to view the low-level device status.

[fiddylamar-svg]

I used putty as suggested, I'm assuming that nothing is happening with the mma6451q, with all the readings being 0?

[fiddylamar-svg]

Here's my soldering btw... I think the connections are fine but Im worried I burnt through the traces or something.

[mjrgh]

By the way, regarding the "clone", I didn't notice that that doesn't actually claim to be an MMA8451Q, but rather 8452, so that might explain the problem. The name sounds so close but it could be a completely different register set. I'd never expect any I2C device to work with a given piece of software unless it's exactly the same device the software is designed for - this is one of those cases where close isn't usually good enough.

[fiddylamar-svg]

Yeah on this ebay listing it's listed as 8452 but I actually got the same board from aliexpress and it was listed as 8451. However on both boards, they are marked as 845X

However I'm not that dissapointed that the "clone" didnt work, i knew it was a long shot and it didn't cost much.

[mjrgh]

The soldering is probably fine - PCB traces are usually pretty robust.

One thing you might try is removing the interrupt: line from the config, in case the INT1 connection is the problem. The I2C connection seems to be working, but the software apparently isn't even trying to read anything, which makes me think it's not getting interrupt signals (since that's what triggers reads when operating in interrupt mode).

You can also try manually reading the XYZ registers, from the console:

i2c0 --rx $1D $01 6

That'll read the six bytes of the XYZ registers, so we can see if those are reading back as all zeroes every time. Normally those will be fluctuating as the device picks up small vibrations.

[fiddylamar-svg]

Once again, thankyou for response. Hopefully we'll figure out what the issue is.

Removing the interrupt line from the config.json does not fix the issue and produces the following log:

2025/08/08 20:12:29 Info: Flash JEDEC ID recognized as Winbond W25Q16JV-IQ/JQ, capacity 2097152 bytes
2025/08/08 20:12:29 Info: SFDP basic parameters table found, capacity entry found [4:7]{ ff ff ff 00 }, 2097152 bytes
2025/08/08 20:12:29 Info: Flash file system mounted; 131072 bytes allocated to 2 files
2025/08/08 20:12:29 Debug: File "config.json" opened for read, 32570 us
2025/08/08 20:12:29 Config: Config file loaded OK; parsed JSON memory usage: 5,328 bytes
2025/08/08 20:12:29 Info: I2C0 bus reset OK, 0 clocks sent
2025/08/08 20:12:29 Config: I2C0 configured on SDA=GP20, SCL=GP21; speed: 400000; DMA channels: TX 0, RX 1
2025/08/08 20:12:29 Error: mma8451q: invalid interrupt GPIO port
2025/08/08 20:12:29 Config: Open Pinball Device HID configured
2025/08/08 20:12:29 Config: USB CDC console enabled, output buffer size 8192, history size 256
2025/08/08 20:12:29 Error: nudge.source: no matching device for "mma8451q"
2025/08/08 20:12:29 Info: Flash struct 'null.acc' not found (flash storage status code -1); using defaults
2025/08/08 20:12:29 Config: Nudge input configured on Null Device; nudge x = device +X, y = +Y, z = +Z
2025/08/08 20:12:29 Info: Kb LED 01

Testing for bytes using i2c0 --rx $1D $01 6 returned fluctuating byte readings:

So I presume that's a good sign that the device is somewhat functional?

[mjrgh]

2025/08/08 20:12:29 Error: mma8451q: invalid interrupt GPIO port

Did you just delete the interrupt: line entirely? DON'T change it to "-1" or anything like that - you have to actually delete it.

[fiddylamar-svg]

Yes, this is what code looked like after removing the interrupt line::

mma8451q: {
   i2c: 0,        // which I2C unit you're using - 0 if you connected the device to I2C0 pins, 1 for I2C1 pins
   addr: 0x1D,    // the chip's I2C address - 0x1C if you connected "A" (SA0) to GND, 0x1D if you connected it to 3V3 OUT or left it unconnected
   gRange: 2,     // the "g" range to select - 2 selects +/- 2g, which is the most sensitive setting, and usually the best for virtual pinball
},

This is the log that occurs on boot:

[mjrgh]

Oops, I took a quick look at the interrupt: parsing and caught a bug in the code. I'm attaching a patch with a fix for that.

MMA8451Q-Intr-fix.zip

[fiddylamar-svg]

Thankyou for helping me through this!

Is it possible to donate a kofi or something like that?

[mjrgh]

From your ad hoc register reading, it does look like the chip is producing readings, so I continue to suspect the INT1 connection. Double-check that you have the breadboard wire connected to the INT1 pin (not INT2). And in any case, the poll-mode test (using the firmware update) will also help test that proposition.

[fiddylamar-svg]

I am certain that the INT1 pin has always been connected to the Interrupt pin on the Pico (assigned to GPIO 0). I am looking at the connections and it is still the case.

[fiddylamar-svg]

OK I think I figured out the problem, I'm getting readings now :)

I changed the interrupt from GPIO 0 to GPIO 1. I did this because I noticed the GPIO 0 was making a signal in the Buttons tab, even when nothing was connected to it. (see below)

I also pushed down on the pins in the breadboard , not sure if that helped.

I think this is resolved, still not sure why GPIO 0 is triggering but I can look into that.

Thank you for your help with this!

[mjrgh]

Good catch on GP0! I don't know what would be causing that noise problem either. It might be worth re-flowing the solder on the Pico header pin at GP0, in case it's a bad solder joint. (Just hit it with the soldering iron long enough to melt the solder. You can also add a little bit more solder if it looks too thin there.) It's also possible that the breadboard or the jumper wire is flaky at that location - those little pre-built dupont wires sometimes have loose crimps at one end or the other, so jiggling them can change the behavior. It can be maddeningly difficult to track down flaky connections like that, since just touching the setup can flip it between working and non-working, or it can just change seemingly spontaneously, because of ambient vibration. If you suspect something like that you can always swap the wire for a new one.

[fiddylamar-svg]

Yeah, I'll have a look at that pin.

Thanks once again and if there's anyway I can donate to you please let me know, I really appreciated this help!