USB Host Capacitance Advice

[lemmings]

Hey everyone, I'm making a teensy synth that I want to be able to play with my m-audio mini usb-only keyboard--and plug directly into the teensy synth without any computer or USB-DIN/Serial converter. I've decided to use a Seeeduino (SAM21 mcu with USB host capability) as a usb host board instead of the Arduino USB host board (cheaper, smaller). The PJRC guide suggested using at least a 120uF capacitor just to account for the sudden current draw that occurs when plugging in a USB device that will be powered from the same source as the teensy. Does where I place the 120uF especially matter? Should I place it right in front of the Seeduino VIN or near the Teensy VIN, or does either work? Also, is there a reason the guide suggests only a 100uF capacitor if not using a power supply? USB Host Shield Library, For Connecting Other USB Devices

I'm only planning on using small low power mini keyboards with this project, so I am not worrying too much about needing a power supply, I think the standard 500mA should be fine to run everything. I've attached some screenshots of my schematic if that helps. Also I am using a PowerMUX board and voltage regulator for the optional use of a power supply, the power mux board limits current to 2.0A max. Thank you!

 

[UHF]

Hello, you know that Teensy 4.0 and 4.1 already have USB Host capability? You would be better off with a 4.1, as the host pins have a proper 0.1" pitch plus power management. You can set USB type in Arduino IDE to compile with Serial+MIDI and it's mostly done for you. I use an Arturia Minilab on 3.6 and 4.1 and never had any problems.

Teensy4.1 pinout

 

[lemmings]

Hello, you know that Teensy 4.0 and 4.1 already have USB Host capability? You would be better off with a 4.1, as the host pins have a proper 0.1" pitch plus power management. You can set USB type in Arduino IDE to compile with Serial+MIDI and it's mostly done for you. I use an Arturia Minilab on 3.6 and 4.1 and never had any problems.

Teensy4.1 pinout

Thanks UHF, yes you're right. I decided to just go with the Teensy 4.1 afterall, and yes the power management is nice to have taken care of onboard like that. I was also a little concerned about availability of the Teensy 4.1 and extra cost (the teensy 4.0 plus seeduino is still cheaper than a teensy 4.1 ), but looks like other distributors carry the 4.1 if the PJRC store is out of stock when I need them.