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Thread: USB serial dropping data on Teensy 3.2

  1. #1
    Junior Member
    Join Date
    Jun 2020
    Posts
    1

    USB serial dropping data on Teensy 3.2

    Setup:
    Teensy 3.2
    Teensyduino 1.8.12 on Mac OS 10.15.5
    USB Type: "Serial"
    CPU Speed: 72 MHz (though I've tried many others)
    Direct USB cable, no hubs or anything, no other devices plugged in

    I just installed the current Teensyduino after being away for probably a year. I am having all sorts of really basic serial problems, data is just dropping left and right. Here's an example of a complete program I am running right now:

    Code:
    byte count = 0;
    
    void setup() {
      Serial.begin(9600);
      Serial.println("startup!");
      delay(1000);
    }
    
    void loop() {
      Serial.println(count++);
      delay(100);
    }
    On the Serial Monitor, I would expect that I'd see numbers increasing and rolling over at 255. Here's what I see right now after approximately 10 seconds or so of running:

    Code:
    128
    130
    131
    137
    147
    149
    153
    155
    164
    167
    171
    173
    179
    181
    185
    187
    196
    200
    206
    209
    210
    214
    217
    222
    224
    227
    229
    237
    242
    245
    I just ran it on a Teensy 3.6 (180 MHz) and saw the same thing (not identical numbers dropped, but the same phenomenon of dropping most data). Also tried it on an Arduino Pro Mini and it runs exactly as you'd expect, no missed characters.

    Any ideas? Things to look at that might be weird about my system? It's a fresh install and I rebooted recently. The Serial Plotter shows a sawtooth graph that is similarly imperfect. Thanks for any ideas you might have!

    [Update: Also tried it on a Teensy 4.0, with the same results, most data dropped.]

    [Update 2: I swapped USB cables and all of a sudden it seemed like it was working perfectly for a moment so I thought it was solved. Now I can't replicate that even with the new cable. Argh.]
    Last edited by dgsharp; 06-27-2020 at 02:48 AM. Reason: Not solved after all

  2. #2
    Senior Member+ defragster's Avatar
    Join Date
    Feb 2015
    Posts
    11,780
    Works as expected here :: Win 10 IDE 1.8.13 abd TD 1.52 b2

    On T_3.2 both PJRC Teensy SerMon and TyCommander. ( at 96 MHz )

    On T_3.6 both PJRC Teensy SerMon and TyCommander. and IDE SerMon

    Tried both through HUB and Direct front USB port.

  3. #3
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012
    Posts
    22,094
    Any chance I could talk you into testing with the latest beta?

    https://forum.pjrc.com/threads/61570...no-1-53-Beta-3

    I'll admit, this is kind of a long shot, since little has changed on the Teensy 3.x code since 1.52. But major bugs impacting some Macintosh systems were fixed in Arduino 1.8.13 which the Catalina version uses.

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