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Aaron Turner edited this page Apr 29, 2015 · 2 revisions

Next Generation TeensyDSC: v2.0

So I'm already starting to think a next generation TeensyDSC should look like. v0.5 was effectively a proof-of-concept showing that I could actually design and deliver a simple wireless DSC adapter. v2.0 should take what I've learned and take it to the next level. I hope to bring some of these ideas to the v0.5 hardware with updated software.

What worked

  1. Using the RN-XV wireless module was generally a success. It's relatively easy to use, low power, has strong enough signal and most importantly an AP mode but has a few small issues:
    • Footprint is a bit large for it's feature set.
    • Cost. At $35/ea, it's probably one of the most expensive WiFi modules out there
    • No advanced features like multiple serial ports or TCP server sockets
    • No imbeded processor makes it pretty dumb, but also easy to use
  2. Using the Teensy 3.1 has been awesome. Easy to work with and it's 5V tolerance makes interfacing with the encoders easy. I haven't seen a better solution come out.
  3. Supporting both 12V and USB power was a good idea, but I may switch to only USB to reduce costs (few components and less PCB space). Also, a lot of astro gear is moving to USB and USB power packs are cheap.

What can be improved

  1. Not having a simple "mode" switch is going to make my life difficult to add additional features like web based configuration.
  2. Missing a lot of advanced features that would be nice:
    • No serial ports
    • No support for camera
    • Accuracy with SkySafari could be improved because SF isn't that smart
  3. Need some way of benchmarking the encoders and ensuring I'm not over running the Teensy. What resolution encoders are really supported?
    • Should I use the built-in quadrature decoding feature of the Teensy 3.1?
    • Do we need a dedicated chip like an Avagto HCTL-2032-SC or LSI LFLS7266R1-S? These are expensive though... about $10/ea (LSI is available from US Digital)
    • US Digital sells some other single channel options like the LS7366R which is a single channel with SPI interface
  4. Need to re-layout configuration information stored in Flash on the Teensy. Should be a single versioned struct.
  5. Need to re-think how config is "saved". Make it more seemless to the user even if multiple processors/chips are involved.
  6. Annoying that every time I want to reprogram the Teensy, I need to take it out of the enclosure to get at the mini-USB port

Hardware changes

  1. Switch the WiFi module
    • The RN-XV which I currently use is $35/ea and doesn't have the greatest feature set
    • The ESP8266 is the cheapest @ < $5/ea
      • Has a growing developer community behind it, but seems a little unstable.
      • Unsure of it's true capabilities which are likely to improve over time
    • The Blugiga wf121 has the best featureset but is $30/ea
      • Would really need to find a convincing argument for the Bluegiga's extra serial ports/tcp server support.
  2. Add a GPS module. $15 for a Ublox Neo-6M w/ ant off ebay.
    • Makes it easy to determine current time & location for advanced DSC features
  3. Add a mode switch:
    • Config Mode (web server)
    • DSC Mode
    • Serial port bridge?
  4. Consider using the Teensy 3.1 hardware encoder support on dedicated pins
    • In theory should provide better support then using interrupts?
    • Already has a library available
  5. Break out the D-/D+ pins on the Teensy to the external USB port so you don't need to open the case to reprogram it.
  6. Add a "hold down" button of some sort to make it easier to do a manual alignment
  7. Shutter/focus control ala Nexus
  8. Intelliscope encoder support Looks like I can get a loaner Intelliscope from the SJAA. There's enough information out there that it should be pretty doable and the components required aren't that expensive.

Software Improvements

  1. A SkyCommander mode. We wouldn't need a fancy UI or extensive database, since you'd still need something like SkySafari for finding objects, but instead of sending encoder values, we'd send RA/Dec values like SkyCommander. We would then do the 2-3 star alignment and use Taki's code for compensating for mount errors. Would be really nice to have a specific mode for colleting the necessary info for calculating the Z1, Z2, Z3 error values. Would require:
    • GPS for position & current time ($15)
    • Mode switch
    • UI could be done via HTTP instead of LCD??
  2. Easier config. The serial monitor method is a PITA. Really should be a webserver. Things like the ESP8266 and Bluegiga support running the webserver in the WiFi module.
  3. Easy "reset to factory defaults". Needs to reset the WiFi module as well.
  4. Easier configuration of the WiFi settings. SSID and passphrase at least.
  5. Support joining an existing WiFi network. Would almost certainly require a LCD to show the IP address.
  6. SkyFi web page emulation. Would make it easier to intergrate with SkySafari. No idea what SkyFi web page looks like though. Need to ask around to borrow one.

Open questions

  1. Dew heater
    • Big increase in costs (PCB & components)
      • Really should be a daughterboard
      • Could be done via ribbon cable or direct plugin
    • Requires a lot of pins and probably a LCD display, buttons, etc
      • May make the most sense of using a Teensy LC for the brains and control it over serial. Will need a more robust power supply then the DSC features, so put the +12V converter here.
  2. Add an optional serial port (TTL & Serial) only option. Would be cheaper then the Nexus-S and would skip all the other features. Would run the serial port to the Teensy and just copy bytes between the port and WiFi. Select the port and port options (speed, etc) via the web config
  3. LCD
    • Really not sure about this. Probably only necessary for a dew heater or some other non-DSC solution.
  4. Factory reset button
    • TeensyDSC is a DIY solution, so reprogramming over USB is always an option so not sure this is necessary.
  5. Goto support
    • Limited user base
    • StellarCat support or roll my own stepper motor daughterboard?
      • StellarCat seems to require some kind of serial pass through thingy???
      • I probably could contact them and find out what is actually necessary.
      • Gen3 StellarCat is USB???
    • Seems like a large upfront investment for me. Would require someone with a scope and stepper motors to be involved.
  6. Dave Ek ASCOM support. Would need to know what his ASCOM protocol looks like. I'm guessing it's probably just his published protocol??? No idea really. Would be a nice enhancement though, since it would open up compatibility a lot.
  7. Equatorial Platform Driver. One (or two???) stepper motors. Just need and easy means of adjusting the speed. Honestly, not really sure this "fits" in this project or really should be a separate project. Could probably be done via a TeensyLC.
  8. Built in battery power?
    • Might be easier then I think and would allow for a more unified solution
    • Really depends on total features, Amp draw and finding a suitable enclosure
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