How hard is it to implement a 1984 "simple" hardware communication protocol?
-
I never mentioned computers. In fact, computers just complicate this because MIDI over USB can't do MIDI pass through devices
To err is human. Fortune favors the monsters.
"hard" "music" this is site where posts usually have some bearing to computers/IT industry. So it is the "this is about computers" presumption that governs. When it`s not about computers express mention should be made that isn`t not about computers. When you use the word "hard" and start talking about music you move things in a totally different registry. That`s not something that can be made tacitly. The word "hardware" has one very clear meaning on this site, different from the one it might have on a music industry site. Is CP now suddenly a "rock and roll" website? that`s what it begins to look like if you neglect what I said above.
-
MIDI is a two wire serial protocol. It's a UART with a 5 pin DIN on the end. Literally I should be able to simply type Serial1.begin(31250); // MIDI baud rate And start talking to it. I've been through A USB host controller an ESP32 S2 an ESP32 S3 a MIDI breakout none of the hardware is giving me *anything* from MIDI, neither USB nor standard. I'm getting *another* MIDI breakout today. I hope the old one was defective. If that doesn't work I'm hardwiring a raw 5 pin DIN to an optocoupler and doing the whole elephanting thing from scratch. Nothing like waiting on hardware in order to code something you're pretty sure won't work.
To err is human. Fortune favors the monsters.
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.
-
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.
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.
-
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.
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.
-
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.
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.
-
MIDI is a two wire serial protocol. It's a UART with a 5 pin DIN on the end. Literally I should be able to simply type Serial1.begin(31250); // MIDI baud rate And start talking to it. I've been through A USB host controller an ESP32 S2 an ESP32 S3 a MIDI breakout none of the hardware is giving me *anything* from MIDI, neither USB nor standard. I'm getting *another* MIDI breakout today. I hope the old one was defective. If that doesn't work I'm hardwiring a raw 5 pin DIN to an optocoupler and doing the whole elephanting thing from scratch. Nothing like waiting on hardware in order to code something you're pretty sure won't work.
To err is human. Fortune favors the monsters.
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.
-
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.
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.
-
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.
-
5 pin DIN is a puzzlement, especially as XLRs are more robust, easier to connect and more prevalent in performance situations.
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.
-
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.
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.
-
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.
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.
-
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.
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.
-
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.
Well, all I can say is that the spec. I'm looking at does say UART!
-
Well, all I can say is that the spec. I'm looking at does say UART!
Well, fair enough
To err is human. Fortune favors the monsters.
-
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.
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.
-
MIDI is a two wire serial protocol. It's a UART with a 5 pin DIN on the end. Literally I should be able to simply type Serial1.begin(31250); // MIDI baud rate And start talking to it. I've been through A USB host controller an ESP32 S2 an ESP32 S3 a MIDI breakout none of the hardware is giving me *anything* from MIDI, neither USB nor standard. I'm getting *another* MIDI breakout today. I hope the old one was defective. If that doesn't work I'm hardwiring a raw 5 pin DIN to an optocoupler and doing the whole elephanting thing from scratch. Nothing like waiting on hardware in order to code something you're pretty sure won't work.
To err is human. Fortune favors the monsters.
Assuming you haven't already figured it out, if using a MIDI specific breakout board, are all the pins wired (with appropriate resistors), as show in https://www.midi.org/specifications-old/item/midi-din-electrical-specification ? It also notes that pin 2 must be grounded only on the transmitter (which may or may not make a difference, if the breakout was made for a receiver).
-
Assuming you haven't already figured it out, if using a MIDI specific breakout board, are all the pins wired (with appropriate resistors), as show in https://www.midi.org/specifications-old/item/midi-din-electrical-specification ? It also notes that pin 2 must be grounded only on the transmitter (which may or may not make a difference, if the breakout was made for a receiver).
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.
