Custom Teensy - Schematic Review

[vitormhenrique]

Hello Everyone!

How are you guys and gals?!

I'm working on a custom teensy for few projects, Ideally I wanted a drop in replacement for my current microcontroller that has the same footprint of a arduino mkr zero, but with more processing power and few extra capabilities.

I have designed few very simple boards in the past, but never something as complex as this, so any help is appreciated.

The main difference are the following:
- DYNAMIXEL TTL connectors provide and a shared half-duplex data bus (74LVC buffers).
- Dedicated vertical JST-SH connectors expose one 3.3 V I2C port (stemma / qwiic) and one 3.3 V UART port.
- Higher-ish voltage input though a MPM3610 buck module to 5V, and TLV75733P to 3.3V
- Added small ws2812b led (i find it very useful to have different colors for different status when running robots etc...)

Main page image attached with full schematic as well.

 

[PaulStoffregen]

Looked at this for a few minutes, mostly at the power supply part. Seems like it ought to work. TPS2116 power mux looks like a nice solution for 2 different power inputs.

 

[vitormhenrique]

Thanks very much Paul! no idea if I’ll be able to route this madness.
but I’ll share the files on github after it is finished!

 

[BillFM]

arduino mkr zero shows 14-pin connectors as female. Is this new project supposed to be compatible? I see male pins.

Will an expansion board be placed on top of pcb or underneath pcb? If on top, there will be interference with J8 and J9 unless there is a massive cut-out in expansion board to accommodate J8/J9 or, the 14-pin headers are extra long. DYNAMIXEL connectors are pretty tall. Not sure if there's enough real-estate to rotate J8/J9 90-degrees and use 90-degree connectors such that wires exit parallel to pcb.

Like the idea of WS2812b LED.

 

[vitormhenrique]

I should have said "arduino mkr zero like" board.
Important for me is the form size, mounting holes. I actually remove the female headers on mine and put male at the bottom. It most definitely will not be compatible with "normal shields" as I expose MAIN_VCC over the headers and that is a way higher voltage than the normal arduino uses.
I though about the parallel connectors, but there is no space I believe. But again, I'm a newbie on making dense pcb's like this.

WS2812b led and qwiic connectors are so good, I have a decent collection of sensors, IMU's and other stuff from "sparkfun" and "adafruit" and it makes testing different things much faster.

Maybe @Paul can copy this on a future teensy.

 

[vitormhenrique]

Quick update if someone is interested.
I ended up going on a different route, was not sure I was up for the challenge of routing that board.
Decided building it on top of the MicroMod module, could not keep the same footprint, but got close enough that with some minor changes i can get it working on my robot.
With the advantage that in the future if a faster teensy is available I can even upgrade! awesome. I was also able to fit better reverse polarity protection, proper solder jump for choosing output on TTL ports.
@Paul on future boards, if you want to give it a try the WS2812E-1313 led works fine on 3.3V supply and logic.

 

[vitormhenrique]

Another cool update, ported my firmware to teensy, using freertos-teensy from tsandmann, got all i2c and serial devices working and ran a quick benchmark comparing my previous MCU, teensy is insane, seriously.

Metric	Teensy MicroMod​	OpenRB-150​	Result
MCU	IMXRT1062, 600 MHz​	SAMD21G18A, 48 MHz​	Teensy clock is 12.5× higher
Control loop	108 us mean​	838 us mean​	Teensy 7.8× faster
Controller/gait step	5 us mean​	330 us mean​	Teensy about 66× faster
DXL task, idle	10 us mean​	35 us mean​	Teensy 3.5× faster
RC task	2 us mean​	203 us mean​	Teensy about 100× faster
Health task	4 us mean​	10 us mean​	Teensy 2.5× faster