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Boe Bot Wireless with RF (USB - TTL converter) — Parallax Forums

Boe Bot Wireless with RF (USB - TTL converter)

AmitBholeAmitBhole Posts: 3
edited 2009-08-10 07:12 in Robotics
Hi All,
I have a Boe Bot with USB output (Version J). (Not RS232) and its working fine with USB cable. Now, I want to transfer data from PC (Laptop) to Boe Bot Servo Motors using RF Transmitter (27980) and Receiver (27981), I have both of these. I understand that I need to use USB to TTL converter for RF transmitter and TTL to USB converter for RF receiver. My question is how can I make / buy these converters/adapters ?
At this point of time, I am not willing to send any data from BoeBot to PC .. So I am not installing any Tx on BoeBot and hence no Rx on PC. However I am open to any suggestions, as I may go for it.
Please let me know if any of this information is not sufficient to answer my question.
I appreciate your help.
Thanks
Amit

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2009-07-12 23:40
    The Parallax USB2SER adapter would work for the PC end although you'd have to have a +5V supply for the transmitter.

    www.parallax.com/StoreSearchResults/tabid/768/txtSearch/usb2ser/List/0/SortField/4/ProductID/32/Default.aspx

    FTDI (who makes the USB to serial adapter chips for Parallax and others) makes several USB to serial adapters that provide a small amount of +5V that can be used for the transmitter.

    www.ftdichip.com/Products/EvaluationKits/TTL-232R-WE.htm

    You don't need a USB to TTL adapter on the Stamp end. Just connect the receiver to a Stamp I/O pin. Put a 220 Ohm resistor in series with the I/O pin to protect the Stamp and receiver from programming errors that might set the I/O pin to the opposite state from the receiver and damage the I/O pin.

    Use a SERIN statement with the I/O pin number you're using for the receiver. Read the Manual for the SERIN statement for details. Also look at the receiver and transmitter documentation and sample programs.
  • AmitBholeAmitBhole Posts: 3
    edited 2009-07-13 00:03
    Mike,
    Thanks for very quick and exact solution response. That is what I was looking for.
    Oh, yeah you are right for TTL to USB converter, i don't need that.
    So I need to spend another 20$ .. Thats fine..

    Gr8! .. next weekend will be fun working on these ..

    Thanks again.
    Amit
  • Mike GreenMike Green Posts: 23,101
    edited 2009-07-13 00:30
    I may have given you bad advice. The USB2SER adapter (and the FTDI adapter) produce true serial polarity with the idle state of the data being +5V. The transmitter and receiver idle at 0V (ground). This is called inverted mode. There's no problem on the Stamp end because the SERIN statement can use either option (and the sample programs do this properly). On the PC end, you will need to configure the COM port for inverted mode or add an inverter of some kind between the USB to serial adapter and the transmitter.

    For an inverter, you can use a switching transistor like the 2N2222A or equivalent, connect the emitter to ground, connect the base through a 1K resistor to the Stamp I/O pin and connect the collector through a 4.7K resistor to +5V (Vdd). The collector also gets connected to the transmitter data pin. When the Stamp I/O pin is high, the transistor will conduct and make the transmitter data pin low. When the Stamp I/O pin is low, the transistor will be off and the 4.7K resistor will make the transmitter data pin high.
  • AmitBholeAmitBhole Posts: 3
    edited 2009-07-13 00:44
    So you are saying that I will need an additional logic inverter (using transistor) / USB port setting.. but in any case, I will still need that adaptor, correct? (and I have already placed an order!) .. This information will definitely help. I think I will make an inverter using the transistor.. and will also try to invert logic at COM port .. anyway all this is for learning .. everything helps !
  • ultimateremedyultimateremedy Posts: 29
    edited 2009-07-23 14:08
    Hi

    Can I use Parallax 433 MHz RF Transmitter connected with Parallax USB to Serial (RS-232) Adapter which is connected with BASIC Stamp 1 Serial Adapter to transmit signal from My PC?

    in short

    PC>USB2Serial>BS1 Serial Adopter > transmitter

    Thanks

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    An hour's contemplation is better than a year's adoration.
  • Mike GreenMike Green Posts: 23,101
    edited 2009-07-23 14:52
    You could use the transmit side of a BS1 Serial Adapter to provide an inverted logic signal. You would need a 4.7K to 10K pullup to +5V
  • ultimateremedyultimateremedy Posts: 29
    edited 2009-07-24 12:31
    Mike thank you for your prompt reply. Can you please provide more details how i should connect them. as last night I tried but couldn't send data.
    I connected usb2serial with bS1 adopter and transmitter. BS1 adopter (GND (Vss), PC0, PC1). Connected Transmitter's Vss to BS1. give 5v from battery and Data with (BS1 Adapter's PC0) and tried to transmit using hyper terminal.

    and it didn't work [noparse]:([/noparse]. Now your golden suggestions.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    An hour's contemplation is better than a year's adoration.
  • Mike GreenMike Green Posts: 23,101
    edited 2009-07-24 14:08
    Everything has to have Vss (ground) connected together. You didn't mention a pullup. You have to have that (4.7K between PCI and +5V). PCI to transmit data.
  • ultimateremedyultimateremedy Posts: 29
    edited 2009-07-27 12:58
    thank Mike. I'll run it today.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    An hour's contemplation is better than a year's adoration.
  • ultimateremedyultimateremedy Posts: 29
    edited 2009-08-03 13:32
    Hi

    well i tried it but it didn't work. I'm attaching Image of my PDB. I'm trying to transmit (via BS1 serial TTL) to Transmitter (Tx) which is connected with 2N2222A with 4.7K and 10K resistor. and receiving output with Rx (placed on the same board) connected with BS2-Pin 2.

    Please suggest what I'm doing wrong.

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    An hour's contemplation is better than a year's adoration.
    PDB-I.JPG
    1280 x 960 - 153K
  • ultimateremedyultimateremedy Posts: 29
    edited 2009-08-10 07:12
    any comment???

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    An hour's contemplation is better than a year's adoration.
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