Supported Hardware Flags and Baud Rate on UARTs

[hrsmjjames]

Hi all,

A cross post from https://www.raspberrypi.org/forums/view ... 2#p1510382 as I'm not sure which area is best to post on.

Essentially:

Please forgive me if I've missed another forum post that already includes this information but I've struggled to find anything definitive.

I have a device that requires us to use a 3.3 TTL interface to it. It states in it's documentation: Baud rate – 9600 Data bytes – 8 Parity – None Stop bits - 1 Handshake – None.

I have successfully communicated with it when I use a FTDI USB to TTL Serial Cable (3.3V) but I would like to use one of the PI's UART outputs to do this.

I've gone through the stages of adding to my boot/config.txt

Code: Select all

enable_uart=1                                                                                                          
dtoverlay=pi3-disable-bt  

and if I run raspi-gpio get 14-15 I get:

Code: Select all

GPIO 14: level=1 fsel=4 alt=0 func=TXD0
GPIO 15: level=1 fsel=4 alt=0 func=RXD0

and ls -l shows

Code: Select all

lrwxrwxrwx 1 root root           7 Jul 30 17:10 serial0 -> ttyAMA0

if I use ssty i see the following:

Code: Select all

stty -F /dev/ttyAMA0
speed 9600 baud; line = 0;
-brkint -imaxbel

If I then try and set 1 stop bit

Code: Select all

stty -F /dev/ttyAMA0 9600 cs8 -parenb -cstopb -crtscts -ixon

and then call ssty again I still get:

Code: Select all

speed 9600 baud; rows 0; columns 0; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; swtch = <undef>; start = ^Q;
stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; discard = ^O; min = 1; time = 0;
-parenb -parodd -cmspar cs8 hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl -ixon -ixoff -iuclc -ixany -imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke -flusho -extproc

I can see the flags set but I still can't communicate with the device, its fine however if i use my FTDI USB TTL Serial Cable.

So, is the above config possible using the on-board UARTS? Is there something else interfering with them that I might have missed?

Thanks

[jamesh]

Please don't cross post, it just spreads information out and make it more difficult for people to find.