• Progress

    Monday, November 4, 2013

    11/4/2013— Updates

    We just got in the redesigned version of the boards, check it out! 

    (More pictures)


    We’ll be making another version before manufacturing with some additional routing changes. We’ll send out an update with all the changes as soon as we’re done testing all the new units.

    We’ve also solved the lead time issue with manufacturing that we mentioned in our last backer update. This means we’re on track to ship in February.

    There’s now a dedicated status page for Tessel and all its modules up on tessel.io/status. Check it out and see what we’re working on! Tweet this.


    GPRS (2G)

    We’re waiting to get the PCBs back from our fab house so we can assemble and test the module. The interesting challenge for GPRS is that the peak current draw is 2A during transmissions (USB 2.0 only gives us 500mA). We hope to get around this with careful power conversion and really big capacitors. 

    In this first round of PCBs we’re hoping to test several things:

    • Actual current draw of the SIM900 GPRS module
    • The logic level translator chip. The SIM900 is a 3.0v device instead of the 3.3v that Tessel outputs. So in order to properly talk to the SIM900 we have to step our signals down.
    • Different antenna options
    • Different power conversion and power input options

    Here’s what the schematic looks like to test all that (click for larger version):



    We’ve had a prototype working for a while now, but it was only able to read RFID cards at a distance of about half an inch (1 cm), which was too small for our liking. Over course of the last few days, we’ve gotten its range up to around 3 inches (8 cm), and are happy to report that the module is basically done at this point. Look for a blog post about the debugging and tuning process next week.


    We’ve nearly decided between using the BlueGiga chipset versus Panasonic; we’re leaning towards the Bluegiga. The BlueGiga module has been verified to be detectable by BLE devices and we’re working on getting reliable communications between Tessel and the module.


    We’re still getting some more samples in, but it looks like we’ll be using the VC0706 as our main signal processing chip. This means the camera will be able to give back compressed JPEGs for snapshot.

    As always, thanks for reading! We’re always available on twitter.com/technicalhumanshttps://www.facebook.com/technicallyamachine, or team@technical.io

    Jia, Kelsey, Tim, Eric, and Jon

    #tessel #technical machine #modules #schematic #testing #jialiya huang #gprs #2g #sim #rfid #camera #bluetooth #update

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