# Arduino will not recognise USB ports on my Mac running Sierra

I even mucked around in terminal and am hoping it's not a 'terminal" problem because I have no clue what i am doing. If you can explain in plain speak please respond. i have to teach this stuff in 4 days.

This is the message I get when I try to upload a sketch

• LilyPad USB implements a atmega32u4 with built in USB. it doesn't have any FTDI or CH340 chips. so you don't need to install the mentioned driver files. the driver for this board installs with Arduino IDE itself. if you try to reset the board with onboard switch, the ports should vanish and reappear. try this and let me know what happens. – Tirdad Sadri Nejad Sep 21 '18 at 7:23
• Tried pressing the reset button and nothing happened except the built in LED stopped flash and then returned as soon as I let the reset button go. Nothing changed in the ports. Thanks for answering. K – Karen Butler Sep 21 '18 at 8:52
• interestingly the usb ports appear when i plug in an Arduino uno. but not for lilypad. – Karen Butler Sep 21 '18 at 9:12
• I am a teacher who helps teachers to use LilyPad .... you should really call things by their correct names .... Arduino will not recognise USB ports on my Mac should be Arduino IDE will not recognise USB ports on my Mac – jsotola Sep 21 '18 at 19:37

I spoke to a very clever friend who has had similar problems. The answer lay in downloading the FTDI helper package not just the driver. If anyone else is having a similar problem the website is

https://www.ftdichip.com/Drivers/D2XX/MacOSX/D2xxHelper_v2.0.0.pkg

Just in time for Thursday.

Thanks to all who tried to help.

K

The Lillypad uses the ATMega32U4 chip. This is the same as the Arduino Leonardo and the Arduino Micro, and suffers the same basic issue that they both suffer from.

Basically, the USB connection is driven by the main chip, not by an interface chip as in most other Arduino boards. This gives you increased flexibility (e.g., using it as a keyboard or a mouse) and decreased cost (less components on the board), but at the additional cost of certain problems that you have to be prepared to resolve.

Because the main chip runs the USB connection that main chip must be working properly for there to even be a USB connection. With other boards that isn't the case - you can remove the main chip completely and the USB interface chip will still work. So it is perfectly possible to "kill" the board by installing a sketch on it which stops the main chip from functioning. As soon as the main chip stops functioning the USB stops functioning - and if the sketch that is installed never starts working at all then you never see a USB connection.

Sometimes it is possible to get the USB port to appear for a short period (a few seconds) by pressing the reset switch, but you have to time it right (press reset and immediately select the port in the menu, then press upload, and press reset again just before the uploading itself starts).

The sure-fire fix, though, is to erase the entire chip (along with your installed "broken" sketch) and reinstall the bootloader using the IDE's tools. You'll need either a hardware programmer (the USBASP is dirt cheap and easy to get on eBay) or another Arduino using the ArduinoISP sketch bundled with the IDE.

If you're going to do any serious work or teaching with any microcontroller-based system it's always good to have a hardware programmer available to help recover from problems, no matter what platform you're working with. Remember: if there's a way to break it, kids will find it. And do it.

• This is a brand new out of the box lilypad board with no sketches loaded on it at all. The ports do not appear when I plug in and select "tools". This is the third one I have opened and there is nothing that works. I have tried bot USB ports. Nothing. So it isn't broken. It just won't work. – Karen Butler Sep 21 '18 at 9:35
• Hmm... That is most odd. I'd suspect your USB cable. You should also check this answer: arduino.stackexchange.com/a/46122/4143 – Majenko Sep 21 '18 at 9:49
• i checked it. it is beyond my skill set!. Thanks anyway. Three usb cords too! – Karen Butler Sep 21 '18 at 10:43
• try a computer with Linux or Windows – Juraj Sep 21 '18 at 11:00