Serial giving garbled output

I’m working on a custom linux distro for our customer product. I’ve got a gps that works when I plug it into my windows machine but on linux at the same baud rate I’m getting gabled output. I’ve tested it on loopback and it seems to work fine for loopback other than some extra newlines. I had to manually set the pins to

name: uart1_txd.uart1_txd (0x44e10984/0x984 = 0x0040), b NA, t NA
signals: uart1_txd | mmc2_sdwp | NA | i2c1_scl | NA | pr1_uart0_txd_mux1 | NA | gpio0_15

name: uart1_rxd.uart1_rxd (0x44e10980/0x980 = 0x0070), b NA, t NA
signals: uart1_rxd | mmc1_sdwp | NA | i2c1_sda | NA | pr1_uart0_rxd_mux1 | NA | gpio0_14

stty settings
speed 9600 baud; line = 0;
intr = ^C; quit = ^; erase = ^?; kill = ^U; eof = ^D; eol = ;
eol2 = ; swtch = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;

Any Ideas?

When you say that the gps works on your windows box, I assume it has an “com” interface, i.e. an RS-232 interface.
The BBB does not use this specification. it uses a “3.3v ttl”. serial connection.

there are a few differences,
b: the logic. a ‘1’ on RS-232 is minus 3-25 volt. a ‘1’ on BBB is plus 3.3 volt.

Other things that can go wrong:
b: Using the wrong frame. 8 or 7 databits, 1, 1.5 or 2 stop bits
In all these cases a loopback will work, because the machine uses it’s own specs.

c; there are crappy RS-232 - “ttl” converters on the market.

please look up the RS-232 spec, If you don’t know what you are doing you can easily fry the BBB

success, LP

I added a 232PTTL33 converter and now communication to the beaglebone works but communication from it to the computer doesn’t work. The converter definetly is an improvement but not a complete solution has anyone else had good luck with it?

these units powered by the signals on pins 7(RTS), 4(DTR), and 3(TD). These handshake lines can be in either the high or low condition, but must be present to power the converter.

If there is no adequate power, generating the necessary RS-232 voltage levels does not work.

so… are RTS and DTR active?