Snow White

Just sharing a couple of photos.

The first is my new prototype Pi with a discrete level shifter used to drive the URF I2C at 5V, while using 3.3V over the RPi I2C interface.  The type of MOSFET is not critical as long as its Vgs is much less than 3.3V – many use the BSS138 or 2N7000 – I just used a couple from my stash which fit breadboards better.  The next step is yet another PCB for Phoebe*:

Discrete I2C level shifter

Discrete I2C level shifter

The second is Zoe who I’m in the process of upgrading to the latest Raspian Jessie Lite – this is a start-from-scratch ‘update’ so I’ll blog the step next.

Zoe litening

Zoe litening

Zoe’s upgrade has so far gone pretty smoothly except for one minor glitch with updating to the new networking interface model and not having a GUI.  The one thing that’s made it a lot easier is that I’ve not had to dismantle her at all.  Also, in the past I’ve used a 10-port powered USB hub for WiFi, keyboard and mouse, but here I have a 2-port USB hub attached to Zoe’s OTG USB connector.  In all, that’s made the upgrade process much less painful than I was expecting.


*Nope, this URF won’t work with Phoebe – even with the level shifter, when I updated the I2C baudrate to 400kbps, the simple test program blocked, just like Phoebe’s own URF does on 3.3V. I also ran Zoe at 100kbps by mistake during her litening transformation, and that proved 100kbps is not fast enough to empty the IMU FIFO as fast as it is being filled.

 

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