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I'm replying here because your new comments are in moderation.
This site is about programming, whether it's computers, or MCUs. In this case it's an MCU which acts as a MIDI controller.
It is not a PC. It is little different than the circuitry you find in today's MIDI controllers. I am coding the firmware as well as building the hardware - they're both part of the very same project, so it is within the scope of CP.
I have a substantial reputation for coding IoT here, and most folks in the lounge know me, so I didn't think it necessary to elaborate on all the details of what I was doing. This is simply part of the project.
Edit: I should add, the lounge is for general commentary on the life of the people that post here. Lots of people post things that aren't code related. In fact that's probably 80% of the stuff here, if you count Wordle and such.
To err is human. Fortune favors the monsters.
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What happens if you connect the midi out directly with the midi in (loopback or however one call this)?
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I don't send MIDI out with this device yet, so I can't check that.
I did however, connect the keyboard to the computer successfully using MIDI DINs to USB so I know the keyboard is good.
I think I have narrowed it down in this case to a hardware problem. I think my previous problems were software, but as it usually goes with the most vexing troubleshooting, I was probably dealing with issues on multiple fronts.
I have a replacement piece of hardware coming today and we'll see how that goes. It's even simpler than the module I currently have, and should eliminate some variables from the equation if nothing else. It's also smaller and not one of those insipid Arduino shields I hate so much.
To err is human. Fortune favors the monsters.
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Quote: connect the keyboard to the computer successfully using MIDI DINs to USB
Ok, but also that sounds strange for me. What I thought is, that MIDI is 5mA current loop...
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MIDI to USB cable[^]
There's no loop. It doesn't work like token ring if that's what you're saying. It's basically a simple UART with a 5 pin DIN. The *only* weird thing about it, is MIDI INs are always optocoupled (or otherwise physically decoupled) from the rest of the circuit to prevent ground loops (i think) - otherwise it's a simple 2 wire UART interface (not RS232, as there are no control lines, just TX and RX) - MIDI only uses like 2 or 3 of the five pins . i say maybe 2 because MIDI ins and outs require two separate lines. It is not full duplex at least not over one cable.
I hope all that made sense, and answered whatever you were wondering about. I wasn't entirely clear on what you're talking about to be honest. 
To err is human. Fortune favors the monsters.
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Thank you for your explanations! The only expirience I have with MIDI is to connect my drums to the sound mixer  
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The "current loop" is an old standard (originally used for teletypes I believe), it is still used in many industrial apps, as it's good for noise rejection. Instead of using voltage (such as +/-12V) to communicate, it uses a 20mA on, 4mA off signal. The receiver has a resistor that the current flows through, so it can monitor the current by measuring the voltage. The 4mA off state is used so that no current indicates a broken wire. The standard is also used for sending analog values from sensors. Sorry for the rambling mansplainage.
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Ah, thanks for the explanation. MIDI is just simple UART. In fact, care is taken to avoid ground loops that can transfer noise or hum from one piece of equipment to the next, which means by the standard, MIDI In ports are always optocoupled (or equivalent). They aren't in a ring, either. The cables are half-duplex UART meaning one cable carries either RX or TX depending if it's an In or Out port it's plugged into. Weirdly, they use 5 pin DIN to connect. My guess is the physically large connector is good for stage equipment for a number of reasons.
To err is human. Fortune favors the monsters.
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5 pin DIN is a puzzlement, especially as XLRs are more robust, easier to connect and more prevalent in performance situations.
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I know why they didn't use XLR. XLR is already used for microphones. They don't want to make it so you can insert cables into slots that can damage equipment. You wouldn't want to run MIDI into an XLR with phantom power for example. You might blow up your synth. Remember this stuff is made for musicians who may not be very technical otherwise.
To err is human. Fortune favors the monsters.
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Yeabut mic connectors are 3-pin. MIDI uses 5 pins. XLR connectors are also used for DMX (lighting) cables. Other XLR pincounts are available (obvs), plus colour-coding rings. A stage set-up for a big performance will have hundreds of assorted XLR cables, I just reckon someone missed a trick when creating the MIDI standard.
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I'm looking at the spec. and I don't see TX and RX. It's either MIDI IN or MIDI OUT, so the connection is unidirectional, and it uses a balanced pair at 5V.
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You won't see it in the spec, as the spec doesn't actually say it's a UART. In practice it is. The data line is either your TX line or your RX line depending if it's In or Out (each cable deals with only one of them)
It operates at 31250 baud. In any case I got it working. I had my TX and RX lines crossed like I said.
To err is human. Fortune favors the monsters.
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Well, all I can say is that the spec. I'm looking at does say UART!
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Well, fair enough
To err is human. Fortune favors the monsters.
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It sounds super frustrating, but also irritatingly fascinating. I wonder if there are any books on the subject from the era.
Will you write an article about all of this when you get it all figured out? I would love to read that.
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I fully intend to. I'm a little ways away from it now though. I have big plans.
To err is human. Fortune favors the monsters.
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Doesn't MIDI come in 5v and 3.3v? You might need a level shifter. E.g. ESP32 is 3.3v and won't appreciate 5v input.
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My module has a level shifter and can operate at either. I found the problem eventually. My TX and RX lines were crossed because I was confused about the orientation: I thought TX was labeled like "I go to the TX pin" rather than "I am the TX pin" - don't know where my head was at.
To err is human. Fortune favors the monsters.
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Hardware pins are always labeled from the perspective of the chip they are attached to. If a pin says TX, it means *this chip* right here transmits on this pin, and if you want to communicate between two chips, you connect one's TX to the other's RX.
I know you know all this, HTCW, so just for the benefit of someone else who might not...
Any hardware you find that doesn't follow this convention should be shunned and the designer publicly shamed in the town square -- but I think it's pretty rare overall.
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I did build my own MIDI card for the IBM PC ISA bus in the 80's. The main difference between MIDI and RS232 serial comms is the baud rate needed. I used a 2MHz crystal for the MIDI. RS232 uses 1.8something MHz crystal. The reason is that the baud rate needed for MIDI is not possible otherwise.
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Ah, yeah, because it's not divisible, I get you. In this it's not a problem, as the timing completely configurable via this little ESP32 MCU. They're little beasts.
To err is human. Fortune favors the monsters.
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The breakout works fine. I've tested it with a loop between TX and RX. No lag.
To err is human. Fortune favors the monsters.
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Insignificant attempt to throw we hear ? (8)
Life should not be a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming “Wow! What a Ride!" - Hunter S Thompson - RIP
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