Timeline for MIDI out waveforms very different between two devices
Current License: CC BY-SA 3.0
11 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Dec 4, 2016 at 2:27 | comment | added | Dan | Got it working tonight. The trick was using that optocoupler input circuit. Both waveforms look the same on the scope now. Thanks for all of your help! | |
| Dec 4, 2016 at 2:27 | vote | accept | Dan | ||
| Dec 2, 2016 at 21:55 | comment | added | CL. | Apparently, they use different output circuits. | |
| Dec 2, 2016 at 20:31 | comment | added | Dan | Just curious, any guess as to why the Axiom49 works with my "MIDI input circuit" and shows such a nice square wave on the scope but the Korg SQ-1 does not work with my input circuit and shows a very non-digital looking wave on the scope? Sorry if I'm asking stupid questions or if you've already answered this above -- I'm not very experienced with EE stuff but I'm very eager to learn more about it. | |
| Dec 2, 2016 at 19:43 | comment | added | CL. | The MIDI interface itself does not use a specific voltage; the output/input circuits convert between 5 V logic and the 5 mA current loop. The official circuit can be improved by making Rd 1kΩ and adding a bypass capacitor (see the PC900 datsheet). | |
| Dec 2, 2016 at 19:00 | comment | added | Dan | Also, I see what you mean about it not being RS-232 now. RS-232 is 12VDC serial communication, whereas the Arduino TX/RX pins use 5VDC serial communication. Thanks for pointing that out. | |
| Dec 2, 2016 at 18:51 | comment | added | Dan | I bought a PC900 optocoupler last night to build the official input circuit as provided by the original MIDI specification: Official MIDI input circuit. I'm going to try this tonight. | |
| Dec 2, 2016 at 16:08 | comment | added | CL. | The RX pin would not work with RS-232 signals. | |
| Dec 2, 2016 at 15:42 | comment | added | Dan | I'll try measuring a resistor across pins 4 and 5 tonight when I get home from work. I'm curious though -- my Arduino MIDI IN circuit is reading the Axiom49 device just fine as a 31.25k baud RS-232 signal (I'm assuming that's what I'm reading when I'm using the RX pin on the Arduino with the baud rate set to 31250). | |
| Dec 2, 2016 at 8:06 | history | edited | CL. | CC BY-SA 3.0 |
added 35 characters in body
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| Dec 2, 2016 at 8:01 | history | answered | CL. | CC BY-SA 3.0 |
