To use it, burn `adio.ino` to your Xiao or Arduino using the Arduino software. Work out what serial port is used (on linux it is normally `/dev/ttyACM0` or `/dev/ttyUSB0`). Then call the MATLAB class like so (Xiao can use pin 0–10, arduino requires pin 2–13):
```matlab
s = arduinoIOPort('/dev/ttyACM0',10,0); %parameters: port, end pin, start pin
s.pinMode(2,'output');
s.pinMode(6,'output');
s.timedTTL(2,5); %send a 5ms TTL on pin 2
s.digitalWrite(6,1); %write pin 6 HIGH
s.digitalWrite(6,0); %write pin 6 LOW
clear s; % close the serial port
```
Currently I only use the arduino/seeduino for single TTL commands, I do want to update to enable strobed 8-10bit words (for which I normally use Display++ or a LabJack, but the Xiao/Arduino is just as capable).
---
### Author:  [@stevevanhooser](https://psychtoolbox.discourse.group/u/stevevanhooser)
#### Post date: [April 5, 2021, 12:13pm UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/4 "2021-04-05T12:13:41Z")
Thanks Ian! This is wonderful and now I see your opticka library for the first time. Great stuff there.
Best
Steve
---
### Author:  [@oroymd](https://psychtoolbox.discourse.group/u/oroymd)
#### Post date: [October 7, 2022, 1:26pm UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/5 "2022-10-07T13:26:56Z")
Hi,
Thanks for this code. Everything works well except I’m having a problem with digitalRead. I can digitalWrite on Outputs but when I try to digitalRead on Inputs I get “NaN”. The pinMode of the pin is correctly set to ‘input’.
Any idea?
---
### Author:  [@Ian-Max-Andolina](https://psychtoolbox.discourse.group/u/Ian-Max-Andolina)
#### Post date: [October 10, 2022, 9:32am UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/6 "2022-10-10T09:32:11Z")
I’m stuck out of the lab and it is hard for me to test for a week or so. What code and what board exactly are you using? One thing to try is to use the original Legacy arduino package:
> **[Legacy MATLAB and Simulink Support for Arduino](https://www.mathworks.com/matlabcentral/fileexchange/32374-legacy-matlab-and-simulink-support-for-arduino)**
>
> MATLAB class and Simulink blocks for communicating with an Arduino microcontroller board
It is really easy to install and test (uses the older `serial` command, I modified it to use IOPort…), see if you can use digitalRead there?
---
### Author:  [@oroymd](https://psychtoolbox.discourse.group/u/oroymd)
#### Post date: [October 10, 2022, 11:23am UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/7 "2022-10-10T11:23:04Z")
Yes, sorry I couldn’t find a way to edit my previous post. I already tested it with both the Legacy and current Matlab versions of Arduino support and both work. It’s just the adaptation with the IOPort that doesn’t.
I am using an Arduino Uno with a simple switch on digital pin 2. On the the current/legacy Matlab versions, when I press the switch it reads “1”, otherwise “0”, which is expected.
```auto
s = arduinoIOPort('/dev/cu.usbmodem101',13,2)
s.pinMode(2, 'input');
s.digitalRead(2); % I also tried digitalRead(s, 2);
```
Thanks!
---
### Author:  [@Ian-Max-Andolina](https://psychtoolbox.discourse.group/u/Ian-Max-Andolina)
#### Post date: [October 10, 2022, 2:05pm UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/8 "2022-10-10T14:05:40Z")
Hm, looking at the `arduinoIOPort.digitalRead()` code and I can see one potential problem, I’ll rummage around to find an uno to test…
---
### Author:  [@oroymd](https://psychtoolbox.discourse.group/u/oroymd)
#### Post date: [October 10, 2022, 2:16pm UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/9 "2022-10-10T14:16:48Z")
> [@Ian-Max-Andolina](#):
>
> m, looking at the `arduinoIOPort.digitalRead()` code and I can see one potential problem, I’ll rummage around to find an uno to test…
Thank you, much appreciated!
---
### Author:  [@Ian-Max-Andolina](https://psychtoolbox.discourse.group/u/Ian-Max-Andolina)
#### Post date: [October 10, 2022, 4:37pm UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/10 "2022-10-10T16:37:54Z")
I think the problem is a non-blocking mode typo, try this as the code for `function val=digitalRead(a, pin)`, I also added a bit more error checking:
```matlab
if a.isDemo; return; end
[n, ~, err] = IOPort('Write',a.conn,uint8([49 97+pin]),2);
if n ~= 2; warning(['digitalRead send command went wrong?']); end
[val, ~, err] = IOPort('Read',a.conn, 1, 3);
if isempty(val)
if ~isempty(err);
warning(['arduinoIOPort.digitalRead() failed:' err]);
else
warning('arduinoIOPort.digitalRead() empty');
end
val = NaN;
else
val = str2double(char(val(1)));
end
```
The important bit is `IOPort('Read',a.conn, 1, 3)` which blocks [1] until 3 characters are available, IIRC the read data should be the value itself then a 13[CR] and 10[LF] so 3 bytes in total, but untested and this is from memory, see if it works…
---
### Author:  [@oroymd](https://psychtoolbox.discourse.group/u/oroymd)
#### Post date: [October 11, 2022, 7:55am UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/11 "2022-10-11T07:55:15Z")
It still returns NaN. The `IOPort('Read',a.conn, 1, 3)` part returns an empty matrix.
---
### Author:  [@Ian-Max-Andolina](https://psychtoolbox.discourse.group/u/Ian-Max-Andolina)
#### Post date: [October 15, 2022, 11:43pm UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/12 "2022-10-15T23:43:45Z")
Hm, I just tested with an Uno clone and a Seeeduino Xiao and I do get data back, and it is 3 bytes for digitalRead (`[data CR NL]`). I noticed the first read of the Uno sometimes is delayed, so perhaps you are hitting the IOPort timeout? I’ve tweaked the code a bit for both `adio.ino` and `arduinoIOPort.m`. You can use configure to change the timeouts, e.g. `IOPort('ConfigureSerialPort', conn, 'ReadTimeout=1.5')`, I added a function to wrap this with `arduinoIOPort.m` too: `a.configure('ReadTimeout=1.5')`.
>
>
What happens if you try to use the Serial Monitor in the Arduino IDE directly? You can send commands and read the reply (make sure baud = 115200). So the ascii command to set e.g. pin 4 to input is **`0e0`** , then a digital read is: **`1e`** — in this command-response language the first byte is the command (a number), the second byte is the pin (a letter), the third byte is optional data. To test, you can send **`99`** which should return `0`, or **`X3`** to return the same number, e.g. `3` in this case. This is the “raw” connection so we can exclude any MATLAB issue…
---
### Author:  [@oroymd](https://psychtoolbox.discourse.group/u/oroymd)
#### Post date: [October 16, 2022, 10:07am UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/13 "2022-10-16T10:07:45Z")
Wow, thanks! It does work now. Maybe it’s the USB A-\>C converter I use that added a delay so that the timeout became an issue? What kind of hub are you using?
Thanks again BTW, great work!
---
### Author:  [@Ian-Max-Andolina](https://psychtoolbox.discourse.group/u/Ian-Max-Andolina)
#### Post date: [October 17, 2022, 4:17am UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/14 "2022-10-17T04:17:13Z")
Something is still a bit strange with your setup. The default IOPort timeout is 1 second, and normally you should never hit that timeout; for me the time to open the device is ~13ms and the first digitalRead around 3ms (my arduinoManager is just a wrapper around arduinoIOPort):
```auto
>> a=arduinoManager('board','Xiao');
--->arduinoManager: Ports available: /dev/ttyS0
--->arduinoManager: Ports available: /dev/ttyACM0
>> a.open
===> All possible serial ports: /dev/ttyACM0 /dev/ttyS0
===> Your specified port /dev/ttyACM0 is present
===> Your specified port /dev/ttyACM0 is available
===> It took 0.013 secs to establish response: 0...
===> Basic Analog and Digital I/O (adio.ino) sketch detected !
===> Arduino successfully connected to port: /dev/ttyACM0!
>> tic;val=a.digitalRead(4);disp(['Value was: ' num2str(val)]);toc
Value was: 1
Elapsed time is 0.003512 seconds.
```
In this case I am using a USB3 hub built-in to my Dell monitor. According to LabJack engineers, command-response times are better for USB-2 devices when using a hub, but we are talking about a few ms either way, not a second…
---
### Author:  [@oroymd](https://psychtoolbox.discourse.group/u/oroymd)
#### Post date: [October 17, 2022, 10:52am UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/15 "2022-10-17T10:52:38Z")
Here is what I get with a Teensy4.1. There is quite a variability in the digitalRead. Even more so at the begining of the reading sequence.
```auto
===> All possible serial ports: /dev/cu.Bluetooth-Incoming-Port /dev/cu.usbmodem124098601 /dev/tty.Bluetooth-Incoming-Port /dev/tty.usbmodem124098601
===> Your specified port /dev/cu.usbmodem124098601 is present
===> Your specified port /dev/cu.usbmodem124098601 is available
===> It took 0.016 secs to establish response: 0...
===> Basic Analog and Digital I/O (adio.ino) sketch detected !
===> Arduino successfully connected to port: /dev/cu.usbmodem124098601!
>> tic;val=s.digitalRead(2);disp(['Value was: ' num2str(val)]);toc
Value was: 0
Elapsed time is 0.011491 seconds.
>> tic;val=s.digitalRead(2);disp(['Value was: ' num2str(val)]);toc
Value was: 0
Elapsed time is 0.002888 seconds.
>> tic;val=s.digitalRead(2);disp(['Value was: ' num2str(val)]);toc
Value was: 0
Elapsed time is 0.010729 seconds.
>> tic;val=s.digitalRead(2);disp(['Value was: ' num2str(val)]);toc
Value was: 0
Elapsed time is 0.005121 seconds.
```
For 10000 iterations of digitalRead:
```auto
b = [];
pause(1)
for i = 1:10000
tic;
s.digitalRead(2);
b(i) = toc;
end
>> mean(b)
ans =
0.001013402959300
```
However, digitalWrite is way faster:
```auto
a = [];
pause(1)
for i = 1:10000
tic;
s.digitalWrite(14,mod(i,2));
a(i) = toc;
end
>> sum(a)
ans =
0.432772365000000
>> mean(a)
ans =
4.327723649999997e-05
```
Even then, though, the first writes of the sequence are orders of magnitude slower (ie, the first write is 6.074 ms).
> **[untitled2](https://ibb.co/xqkPgmz)**
>
> Image untitled2 hosted in ImgBB
With an Arduino Uno:
```auto
===> All possible serial ports: /dev/cu.Bluetooth-Incoming-Port /dev/cu.usbmodem101 /dev/tty.Bluetooth-Incoming-Port /dev/tty.usbmodem101
===> Your specified port /dev/cu.usbmodem101 is present
===> Your specified port /dev/cu.usbmodem101 is available
===> It took 0.531 secs to establish response: 0...
===> Basic Analog and Digital I/O (adio.ino) sketch detected !
===> Arduino successfully connected to port: /dev/cu.usbmodem101!
```
For 10000 iterations of digitalRead, we can see there is indeed, a problem.
```auto
b = [];
pause(1)
for i = 1:10000
tic;
s.digitalRead(2);
b(i) = toc;
end
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
Warning: arduinoIOPort.digitalRead() was empty
> In arduinoIOPort/digitalRead (line 237)
>> sum(b)
ans =
8.888205034199996e+02
```
(cannot post the plot, limited by the forum)
However, digitalWrite is still way faster:
```auto
>> a = [];
pause(1)
for i = 1:10000
tic;
s.digitalWrite(3,mod(i,2));
a(i) = toc;
end
>> mean(a)
ans =
2.542173692000001e-04
```
Although, it is not pretty either.
> **[untitled4](https://ibb.co/4KjQ6hM)**
>
> Image untitled4 hosted in ImgBB
This is with the original USB-B to USB-A long cable provided with Arduino Uno with the USB-A to C adapter so, this might be a cause.
Of note, these tests are conducted on my own personnal machine (MacBook Pro M1 Max 2021) and not the one I plan to use for the experiment. So, it runs Matlab through Rosetta. The timings are thus, of course, not too good nor reliable. Nevertheless, the question of why the digitalReads are so inconsistent remains. Maybe there is something wrong with my Uno since the Teensy reading are so much better. However, the reason why the first readings of the sequence are slow eludes me. It is as if the digitalRead should be initialized or something.
---
### Author:  [@Ian-Max-Andolina](https://psychtoolbox.discourse.group/u/Ian-Max-Andolina)
#### Post date: [October 18, 2022, 12:44am UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/16 "2022-10-18T00:44:21Z")
Hm, testing using Ubuntu 22.04 on my Uno (actually it is a chinese clone of a genuine arduino) I get a digitalRead mean of 4.1ms ( ±0.001 SE) and my Seeeduino Xiao as 0.62ms ( ±0.0006 SE):
The Xiao at least has pretty low variance. The Uno is slightly bimodal, and ~4ms would not be so acceptable in a tight display loop. Neither show any increased variance over time. I think your M1 laptop is most of this problem, and on something native it would work more reliably.
As a workaround you can “warm up” the board by doing some digital reads in a loop before any experiment. I tend to do this with all my PTB functions, making sure MATLAB has everything in memory etc.
---
### Author:  [@oroymd](https://psychtoolbox.discourse.group/u/oroymd)
#### Post date: [October 19, 2022, 6:56pm UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/17 "2022-10-19T18:56:04Z")
> [@Ian-Max-Andolina](#):
>
> I think your M1 laptop is most of this problem, and on something native it would work more reliably.
Yeah, most probably. I’m waiting for our new PC to arrive so I can test it on Ubuntu. Thanks for the help!
---
### Author:  [@NaHan](https://psychtoolbox.discourse.group/u/NaHan)
#### Post date: [December 14, 2022, 12:46pm UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/18 "2022-12-14T12:46:29Z")
hi lan-
Thanks for this code.Everything works well except，but when I use a PTB drawing loop，the Risetime change from 70 µs to 0.7 s（when iii \>1757). Do you have any idea about this problem ?
Best!
-NAHAN
> [win, winRect] = Screen(‘OpenWindow’, 2,[],[],32);
> ifi = Screen(‘GetFlipInterval’, win);
> arduino\_u = arduinoIOPort(‘COM9’); %parameters: port, end pin, start pin
> vblTS = Screen(‘Flip’,win);
> timelist = [];
>
> for iii=1:1800
> Screen(‘FillRect’,win, [255 128 0],winRect);
> tic
> arduino\_u.digitalWrite(13,1);
> tt2=toc;
> vblTS = Screen(‘Flip’,win,vblTS+ifi \* 0.5);
> Screen(‘FillRect’,win, [0 0 255],winRect);
> tic
> arduino\_u.digitalWrite(13,0);
> tt4=toc;
> vblTS = Screen(‘Flip’,win,vblTS+ifi \* 0.5);
> timelist=[timelist;tt2 tt4];
> end
---
### Author:  [@NaHan](https://psychtoolbox.discourse.group/u/NaHan)
#### Post date: [December 14, 2022, 12:48pm UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/19 "2022-12-14T12:48:09Z")
---
### Author:  [@Ian-Max-Andolina](https://psychtoolbox.discourse.group/u/Ian-Max-Andolina)
#### Post date: [December 17, 2022, 7:49am UTC](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781/20 "2022-12-17T07:49:47Z")
I can’t reproduce your problem, I tested to 3000 frames using your code at a 60Hz framerate, using Ubuntu 22.04 and PTB 3.0.18 with a Seeeduino Xiao:
My oscilloscope shows a really nice square wave @ 33ms period time confirming the digitial write.
[Next page](https://psychtoolbox.discourse.group/t/serial-port-interface-code-a-performance-comparison/3781.md?page=2)