MatriX build questions

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I am working on the axes PCB, and in the BOM D1 (BAT54) is greyed out (like all the other BAT54 in the BOM) and has a note “Do not fit for MatirX”. But in the actual build guide paragraph 2.6. says otherwise. Do i need it or not?

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I think I am just in front of you for building a MatriX, I think the build guide is out of sync with the current BOM.
I am NOT fitting any BAT54 in the MatriX - none are listed on the BOM - also NOTE that the NOT FITTED part would have been a BAT54S double diode, not the BAT54,235 single diode used elsewhere.
If push comes to shove then it’s easier to retrofit than remove 😃

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latigid on
thanks for the detailed explanation
Mechie
thanks, i will move on then 😉

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The 0V lines are “star wired” back to the main power inlet to try to direct the current flow.* BAT54S diodes shouldn’t be required but if you notice data transmission not working well, a diode should be installed. This is configured as an antiparallel Schottky pair that should connect the 0V lines but keep the voltage within a defined range.

I think it should work with or without them, also probably just bridging the pads would do. There are a few options in any case.

*Of course according to Veritasium the current is induced outside the wires anyway.

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When i want to test the core board communication with the SEQ V4+, i get one green “BLM1 CONN” info on the MatriX display. But it toggles then between CONN and DISC state every 5 seconds. Is this ok in this early stage?
I am not quite sure if i set up the SEQ right, i managed to set BLM_scalar (is this the right one?) to the IN4 port, but i could not find where i set the out port. And the SEQ tells me: Port IN4 (found).
I have just one cable connected from the MatriX to the SEQ - BLM/OUT4 connector.
I did not do a FW upgrade on the SEQ in a while, is this mandatory to do first?
Thanks

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@Enginerd_0x12F - yes, it should be good if both devices listed the other as “seen”, then you have send and receive connectivity in both directions. Some MIDI cables don’t have all 5 pins, so this test makes a lot of sense, also to test your MatriX core.

Regarding the connects/disconnects: there is an inbuilt 5-second reconnection handler, so this might be the reason you see reconnects.

It’s not at all necessary to do right now, but i’d recommend to upgrade SEQ v4+ to the newest version listed on the MatriX page - this implements a bugfix in MatriX CC mode for SEQ v4+:
https://www.midiphy.com/en/matrix/

You can also test the other port (BLM2 on MatriX) and test with a LoopA, if you have it available 🙂.

But i think it looks good - enjoy the rest of the build and have a good weekend!
Best regards,
Peter

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Hawkeye wow, thanks for the fast reply!

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I am trying the first tests of the Matrix with my Loopa.
Peter writes: “… make sure you upgrade to the newest LoopA firmware revision first and also make sure that the MatriX is enabled in LoopAs setup screen.”
Updated Loopa to V2.09 B3, but in setup screen, I cannot find any option to enable MatriX. What did I wrong?
BR
Robert

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Hi Robert - it should be enabled by default, if you plug in a standard MIDI cable (all 5 pins need to be wired) into LoopA’s BLM port and into MatriX BLM 1, you should see a “Connected” message in the MatriX hardware test screen (when no micro SD card is inserted).

Best regards,
Peter

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Hi Peter,
does not work.
To check, if LoopA’s BLM output is working at all, does it send actively any signals to the MatriX, that I could measure with a sope or LED?
BR
Robert

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Hi Robert,

Silly question but are MatriX’s optocoupler chips installed? Also, is your MIDI cable fitting in properly? With the case top in, most plastic-molded cables won’t fit. You need to shave off a bit of the plastic there.

You can also test connectivity from SEQ v4+. You need to set up the so-called “BLM SCALAR” port -> IN4 from the MIDI menu. The message will change to (FOUND) when it locates a BLM device.

I don’t know myself, but I think both SEQ and LoopA should “ping” a few MIDI bytes quite regularly.

Best,
Andy

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@Robert MatriX will initiate the bidirectional communications, it will try sending a SysEx handshake on both of its BLM ports every 5 seconds.
LoopA will listen and answer to these requests but will not initiate communications on OUT4/BLM on its own.

You should see packets arriving from MatriX on IN4 on LoopAs MIDI monitor screen - if you see nothing here, either the IN circuit on LoopA (i.e. optocoupler as Andy wrote), the MIDI cable or the connector may have a problem.

Here’s the pinout of the BLM port/cable, if you want to attach a scope and see if MatriX is really sending the init handshakes:
https://forum.midiphy.com/d/7-loopa-blm-splitter-cable-schematic

If MatriX sends the package and LoopA responds, you could check the input optocoupler on MatriX with the scope, to see first if the data arrives and then if the optocoupler passes it on to the microcontroller.

Best regards,
Peter

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Thanks to that information, I could see that MatriX correctly sends out some heartbeat to the MIDI cable.

I opened my beloved LoopA and I could track this signal to pins 2 and 3 of the opto coupler. Pin 6 should reflect the corresponding signal but keeps always on 5V. I already changed the opto coupler.
I cannot see any mistake here, mysterious. Do you have any idea?

Is the front led labeled “BLM” hard wired to this signal?

BR
Robert

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Hi Robert,
Could you check that the signal makes it back to port PD2 on the Waveshare board?

Could it be that the diode D7 has incorrect polarity or your pull-up/pull-down resistors are not correct?

Best,
Andy

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Thanks Andy. The components on LoopA seem ok. When I put some current into the LED of the opto coupler, it does switch.

Now I assume, that the MatriX does not deliver correct power. Measuring both LED lines from the MatriX shows that both signals do have same phase and minimal differences. These differences were enough to drive my test LED, but not an opto coupler.
Do you have a snippet about the MIDI LED driver part of the Matrix? I guess, the anode is driven by a GPIO port of the waveshare and cathode grounded?

BR
Robert

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Hi Robert,

Sure thing:

Best,
Andy

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220 Ohm?
Shame on me, I confused the resistor values between boards. I was not aware, that each board starts with R1 again. After replacing 20 resistors, I have now the BLM connection established.
Thank you for your immediate help!

BR
Robert

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No problem at all! Good luck with any remaining steps!

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So, moment of truth has come, but with very frustrating result. MCU is booting, test screen o.k. but neo boards do behave very strange. Can I test the boards separately? When I connect them individually, each bord shows other obscure led lighting: sometimes only a few were lit, sometimes all of them (except the last board, which never showed up yet) are weakly glowing, one time I managed to light them all, so I guess @ it is not based on a broken chain or weak power supply. Same when I change the power cables from board to board. Then I noticed the MCU is getting to hot. Could not touch it any more whortly after turning it on. So I decided to stop further testing…

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Sure, you can plug one board in at a time. Heating up can be attributed to reverse power or short circuits, so check

PSU polarity (must be center-positive). Also, what PSU are you using?
Series diodes on each board
Cable harness: was it wired properly? Do check that the connection is really solid. An intermittent contact here can make things very weird.
Voltage regulator orientation
IC orientation

Measure resistance across any 100nF capacitor to see if you short-circuit the +5V supply anywhere.
Do you have a wirescanner board? Please check the cables for shorts and missing contacts.

If you post some photos, I might be able to spot something amiss.