CODEWITHSUNDEEP
serial-portbeagleboard
Zhani Baramidze
Zhani Baramidze

Reputation: 1497

max232n with beaglebone serial

I have USB 2.0 to Serial Adapter LogiLink, which gives rs232 voltage, so I use max232n chip to get 5v, then I connected it to beagleboard J1 header and set up minicom correctly but during booting I get strange characters (like http://pastebin.com/KtCQG6jK) What can be the problem? for max232n I use power source from beaglebone, its supposed to be 5v but its 0.4v, can it be the problem? is it necessary to have DC power source to make it work

Upvotes: 0

Views: 666

Answers (1)

sawdust
sawdust

Reputation: 17067

The hardware documentation for the BeagleBone Black states that

UART0 access via 6 pin 3.3V TTL Header.

and

Expansion Header Usage

There are several precautions that need to me [sic] taken when working with the expansion headers to prevent damage to the board.

ALL VOLTAGE LEVELS ARE 3.3V MAX.

"3.3V TTL" means that the UART's TxD and RxD signals are logic levels of 0 to 3.3 Volts (and not the proper RS-232 levels).
You have and are trying to connect a MAX232N converter, which is for 5V TTL.
Instead you need to be using a 3.3V converter, such as a MAX3232, to match the logic levels used on the BeagleBone Black.

Also double check that you have the baud rate, char size, parity and stop bits correct on the PC side. 115200 8N1 is typical on these embedded devices.

Note that the MAX3232 (and similar chips) should be supplied with 3.3V for Vcc when using 3.3V logic (i.e. it can work with either TTL or CMOS). Supplying 5V to a MAX3232 would be the same as using a MAX232.

Upvotes: 1

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