BT BlueSMiRF -v2.11 Zapping lilypad

Development Boards MicroMod
1

Hi (newbie question)

I just perchased a BlueSMiRF -v2.11 gold bluetooth to connect to my lilypad.

In the feature descriptions it indicated
-Do not attach this device directly to a serial port. You will need an RS232 to TTL converter circuit if you need to attach this to a computer.

What do they mean exactly ??

But in the Leah Buechley’s picture of this set up, she seems to have attached directly to the lilypad.

I want to test it , but don’t want to zap my lilypad. I have search the web but haven’t found much.

Any response on this would be great.

Thanks a million

phil

2

Do some research on various types of serial port.

When you connect things that you want to talk over serial, they need to be talking the same type of serial.

The two most common types are “RS-232” and “TTL”.

The “danger” comes when you try to connect different types together. The lilypad and bluesmirf are both TTL devices, so you can connect them together directly.

The warning is saying don’t connect the bluesmirf to a RS-232 serial port. Your homework is to work out why! Report back here by tommorow, minimum of 100 words.

3

[quote/]

The warning is saying don’t connect the bluesmirf to a RS-232 serial port. Your homework is to work out why! Report back here by tommorow, minimum of 100 words.[/quote]

Microcontroller have a serial port called; SCI

Microcontrollers generate logic signal (TTL) to communicate to another chip but do not generate the proper voltage required for connecting to RS-232 devices.

Types of serial :

RS-232: the standard serial communications interface found on all types of equipment such as computers, modems, printers, Microcontrollers.

Voltage range is; logical 0 are from +5v to +15v.

Logical 1 are from -5v to -15v

TTL : Transistor–Transistor Logic (Voltage range =0 and +5)

signal inputs and outputs of electronic equipment may be called “TTL” inputs or outputs, signifying compatibility with the voltage levels used.

So basically, to connect a microcontroller SCI port to a true RS-232 device, I need to convert the TTL voltages of 0 and +5 into voltages between about -10 volts and +10 volts.

Thanks for your help trialex. Now I just need to learn how to do this without burning anything ($$$) ; )

phil

4

Look at the MAX202 or MAX232 chips - they convert TTL to RS232.

5

n1ist:
Look at the MAX202 or MAX232 chips - they convert TTL to RS232.

Thanks for the advice n1ist.

But if you look closely in in trialex’s reply :

The lilypad and bluesmirf are both TTL devices, so you can connect them together directly.

So i did connect them together and everything seems to work fine except that I seem to have a problem uploading my sketches to the lilypad.

If your interested here is my new post in the arduino forum:

http://www.arduino.cc/cgi-bin/yabb2/YaB … 697702/0#0

Thanks a lot for your help

because of you guys i’m learning a lot

phil