Can use 3.0V for USB?

Hi All,

I am modifying a product ( says Product A ) from USB connectoin to Bluetooth.

It is very simple to do a RS232 replacement.

But the output originally is USB, that is a trouble. I need to use a USB (host?) chip to ouput RS232 signal, and one more level shift for my final Bluetooth UART input.

My Bluetooth is 3V. The product A use USB as power, and I measure the VDD and GND is 5V ( when original Prodcut A operating ).

Does that mean I can only use 5V for product A ( so I need a PWM ? if I use battery 3.0V)

Does it possible to use 3V for Product A.

because I think every chip has its own operation range.

but my co-worker just tell me, 3V seems not enough, why say so ? becaues it is not in USB range?

or he is wrong?

Best regards, Boki.

Reply to
Boki
Loading thread data ...

OK....

Not quite sure what you mean by this. There are RS-232 to USB converters, for PCs that can be used to implement a serial port in a PC. I don't see how this would be of much utility to your application though. I don't see how you can say that converting between USB and RS-232 is easy.

There are many differences between RS-232 and USB, besides the voltage levels. First, USB is a single master, multiple slave protocol that utilizes differential transmission with packetized communication and different types of transactions. RS-232 is a point to point, ground referenced communication channel. Even if you solve the electrical differences between the two, the communication protocols are wildly different and so translating between the two would be very difficult.

Yes, the USB specification says that the power and ground supplied by the USB bus is 5Vdc.

If you need a different voltage you can use a regulator, with the type depending on your power requirements. Keep in mind that there are limits to the amount of power you are allowed to draw from a USB bus.

No Idea, since I don't even know what Product A is. If it is a commercial product that is meant to be supplied by 5V it probably won't work with a 3.3V supply.

Good Luck!

Reply to
Noway2

It doesn't make it better if you use more words.

DNA

Reply to
Genome

do they have to be the right ones?

martin

Reply to
martin griffith

Well, as long as you don't tell us, what Product A is, I doubt the last sentence very much. Just because there is the word "serial" USB doesn't mean that it is remotely compareable to a serial RS232 connection.

The first thing I would check: is there a Product B that is available with Bluetooth. Even if it is expensive, you can save yourself weeks and months of work (and learning the basics).

Second, your Product A (gosh, I hate this!) may already have an RS232 on board. Many manufacturers have taken their old RS232 designs and simply slammed a USB-to-serial converter in front of them to "modernise". Check, if there is an FTDI chip close by the USB connector. If not, forget it.

If you device was built to run at 5V, it'll very very likely not run at

3V. Have you ever taken a hair dryer that runs at 120V to country that uses 230V's? Or vice versa?
Reply to
Matthias Melcher

¡¡¢£¢£¨¬¨¬¨¬¨¬¨¬¨¬¨¬¨¬¨¬¨¬¨¬¨¬¨¬¢£¢£ ¡¡¡¡¡¡µ?ç½õ¸òº?ò´õ?¤?÷??¤ò¾?ðÃ? ¡¡¡¡¡¡ ¡¡¡??·¤¤¥?í¥?£¡¼¥ë¤?³¤???¤é¡Û ¡¡
formatting link
?ÚÃË??²ñ°÷ÂçÊ?Ãæ¡?Û¡¡Âþº£¡¢10,000±ß?¥??¥ó¥ÈÃ?¡¡¿·µ¬²ñ°÷ÅÐ?¤?°???Î????ä?ª¤ê¤?¹¡£¡¡ÃË??²ñ°÷¤ÎÊý¤?ÏÆÃÊÌ?ÂÔ?¤?¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡á¾?·¤¯¤?³¥??é¡á¡¡
formatting link
?¸å¤?¹¤°¤?´ÍøÍ??­¤?¹¡£¡¡¡¡¤?¤«¤·¤¿¤é¡Ä¡¡½÷??¤«¤é¤?ª?¤¤¤¬¤¢¤?¤?¤ì¤?»¤ó¡Ä ¡¡¤ª¼ê¿ô¤?¹¤¬¡¢¥?¥ëÇ?®ÉÔÍ??ì¹ç¤?³¤??é¤??ª´?Ã?·¤?¹¡£ ¡¡office_news snipped-for-privacy@yahoo.co.jp

Works for me!...

DNA

Reply to
Genome

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.