Shop OBEX P1 Docs P2 Docs Learn Events
Propeller chip/other microcontrollers — Parallax Forums

Propeller chip/other microcontrollers

Adam BrooksAdam Brooks Posts: 5
edited 2010-04-30 15:27 in Propeller 1
Hello,
I am currently working on a new design for a prosthetic hand and am looking for a good microcontroller. I need to be able to read analog signals thermal and pressure sensors on the device as well as provide 4-8 PWMs simultaneously. Would this be the best microcontroller to use considering the different COGs and is it possible to work with you guys to develop a smaller form factor board after the first prototype is tested.

Thanks,
Adam Brooks

Comments

  • LeonLeon Posts: 7,620
    edited 2010-04-30 03:02
    How many sensors and analogue signals? Does it need to perform stuff like inverse kinematics?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Leon Heller
    Amateur radio callsign: G1HSM

    Post Edited (Leon) : 4/30/2010 3:08:05 AM GMT
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2010-04-30 03:03
    The Propeller does not have any A/D conversion really but it is a really great micro that I would recommend to almost anyone. However you will need an external A/D to suit. Have a look at my thread and on-line doc as I am doing a very small form factor module with 12-bit A/D and D/A that might be good for you to prototype with.

    http://forums.parallax.com/showthread.php?p=901459

    BTW, welcome to the Propeller forum

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    *Peter*
  • KyeKye Posts: 2,200
    edited 2010-04-30 03:04
    If you don't mind learning how to you the propeller chip you'll find its more than able to do what you just asked above.

    Please post more of the project details and other forum members should be able to help out.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Nyamekye,
  • mctriviamctrivia Posts: 3,772
    edited 2010-04-30 03:06
    you can easily do a sigma delta AD converter on the prop using a few passive extra components costing about $0.006 total in quantities of 5000. Only disadvantage is it takes 2 pins per input.

    8PWM + 8 Analog would still leave 4 pins free.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Lots of propeller based products in stock at affordable prices.

    propmodule.com will be closed May 1-10th. Orders made in that time will be shipped on the 11th.
  • Mike GreenMike Green Posts: 23,101
    edited 2010-04-30 03:09
    There's an object in the Object Exchange that can provide as many PWM outputs as you want using a single cog. The ADC function is documented in the application note (AN001 - www.parallax.com/tabid/832/Default.aspx).

    The built-in ADC function uses one of the two identical counters in each cog, so you'd have to devote one cog for each pair of ADCs with the cog's processor doing some of the work. Each ADC channel also requires two I/O pins, two resistors, and two capacitors mounted close to the processor's I/O pins. Look at the SpinStamp pictures to get an idea of how small you could package the Propeller along with its crystal, EEPROM and voltage regulator. It all fits on a 24-pin DIP module. www.parallax.com/StoreSearchResults/tabid/768/List/0/SortField/4/ProductID/448/Default.aspx?txtSearch=spin+stamp

    There's also the PropStick which uses a 40-pin DIP module which brings out all the I/O pins and includes a USB programming interface that can be used for ordinary serial communications as well. www.parallax.com/StoreSearchResults/tabid/768/txtSearch/propstick/List/0/SortField/4/ProductID/411/Default.aspx

    Post Edited (Mike Green) : 4/30/2010 3:14:12 AM GMT
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-04-30 03:18
    You can always use a cheap analog multiplexer if you're low on available pins for the sigma-delta A-D. A 74HC4051 8:1 multiplexer is less than twenty cents in quantity and can give you 8 analog inputs using five Prop pins. Two such multiplexers yield 16 analog inputs using six pins, plus one inverter. This latter configuration, in fact, is being used in the upcoming S2 robot for its 16 analog input channels.

    -Phil
  • Adam BrooksAdam Brooks Posts: 5
    edited 2010-04-30 03:18
    no real inverse kinematics just need it to run the major actuators I am creating and carry out thermal sensing and maybe stretch for position of the joints. Maximum I need to read 8 thermal sensors sampling as fast as possible and optionally 4 stretch sensors. Also need to generate/ have IO capability for 8 boost converters I am building as well as 8 additional pulse widths/pins. So i guess what I am looking for is the ability to "read" minimum 8 thermal sensors and maximum 12 total sensors. Also i will need output capabilities for 16 devices. I like how there is parallel so that it could handle other stuff is there anything out there for bluetooth/wifi.

    Thanks,
    Adam Brooks
  • mctriviamctrivia Posts: 3,772
    edited 2010-04-30 03:20
    May I offer you a risk free guarantee(well almost). I am so sure that you will like the prop and find it useful that if you order one from me I will let you return it within 6 months(as long as in good working order) for full refund. All you have to pay is the shipping back to me. Please note you should make your order before 2PM CST to be guaranteed I will get it shipped before my vacation.

    I have a propplug in stock also. if you need it just add $15 worth of blank pcbs and write me a note that you want the adapter.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Lots of propeller based products in stock at affordable prices.

    propmodule.com will be closed May 1-10th. Orders made in that time will be shipped on the 11th.
  • mctriviamctrivia Posts: 3,772
    edited 2010-04-30 03:23
    there are many wifi and bluetooth modules available. there is also a usb driver(believe still in works) that will let you use cheap $2 usb bluetooth modules once done. I can't recommend any because I have not played with RF devices since school.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Lots of propeller based products in stock at affordable prices.

    propmodule.com will be closed May 1-10th. Orders made in that time will be shipped on the 11th.
  • Mike GreenMike Green Posts: 23,101
    edited 2010-04-30 03:24
    You're probably going to want to use an external ADC, maybe a pair of 8-channel devices. With fast SPI devices, you'd need 4 I/O pins per device (so you could read them in parallel). With 16 outputs, that's 24 I/O pins. That would leave you with 4 completely uncommitted I/O pins plus the 4 that have other uses during initialization (28-31)
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2010-04-30 03:27
    Sensor acquisition normally requires some stable and precise conversion which the Prop's sigma-delta solution is not. But if it is OK then good. What resolution do you need and what is the sampling rate going to be? Also, what type of actuators are you looking at? One of the modules mentioned at the end of the PUPPY document is actually a quad half-bridge and each driver can operate up to 100kHz (or more) while sinking/sourcing 5 or so amps at up to 30V.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    *Peter*
  • TubularTubular Posts: 4,717
    edited 2010-04-30 05:50
    Mike Green said...
    You're probably going to want to use an external ADC, maybe a pair of 8-channel devices. With fast SPI devices, you'd need 4 I/O pins per device (so you could read them in parallel). With 16 outputs, that's 24 I/O pins. That would leave you with 4 completely uncommitted I/O pins plus the 4 that have other uses during initialization (28-31)

    Some ADC objects (such as MCP3208_fast) tie the DI and DO together, so its really 3 pins per 8ch ADC. With some effort it should be possible to common up the CS's, perhaps even the clocks, to get down to 4 pins for 16 channels at 50kHz.

    I only mention this in case the OP is tight on pins...
  • pjvpjv Posts: 1,903
    edited 2010-04-30 15:27
    Hi All;

    Depending on accuracy requirements and sensor configuration, then writing your own assembler ADC and not using the internal counters, you can get a nice 12 bit Sigma Delta to work very well with only a single pin, and the software is simpler than serial communications to a external device..... none required!

    Cheers,

    Peter (pjv)
Sign In or Register to comment.