Max232 level shifter

[achourwissem]

Posted on July 05, 2013 at 12:02

hello

i have usb <-> R232 converter and i want to make it receive correct characters from stm32f4 board , so which capacitors i have to use with max232 to realise this ? and thnx :)

[Tesla DeLorean]

Posted on July 05, 2013 at 16:50

What does the part documentation tell you about the voltages and capacitors?

[achourwissem]

Posted on July 05, 2013 at 17:43

i posted in other forum and many answered that u can control output voltage by changing the value of capacitors . so if it's wrong , can u propose for me a solution ?

[msfassarella]

Posted on July 05, 2013 at 19:56

You can use anyone between 100nF ~ 1uF. It can be changed with the distance and the amount the noise of enviroment. Only be carefull, MAX232 need a voltage supply of 4.5V to 5.5V and most stm32 boards are using 3.3V regulator. Maybe will be better use a MAX3232 that support a voltage supply of  3V to  5.5V.

[achourwissem]

Posted on July 05, 2013 at 20:03

thnx so did u tried before that marge of capacitors values 100nF ~ 1uF with max232 to interface  stm32f4 and and pc via usb <-> r232 adapter ?

[achourwissem]

Posted on July 05, 2013 at 20:09

Because generally they meant by it the level +/-12v for the rs232 <-> r232 cable

[Tesla DeLorean]

Posted on July 05, 2013 at 21:12

The MAX3232 w/0.1uF parts at 3.3V is much more likely to have outputs closer to +/-6V, which would meet EIA/TIA-232-F and EIA/TIA-562

http://pdfserv.maximintegrated.com/en/ds/MAX3222-MAX3241.pdf

If you read the documentation you'd be able to do the design work yourself, rather than ask questions that demonstrate you haven't.

[achourwissem]

Posted on July 05, 2013 at 21:51

thank you clive i hope it will work :)