SerialPort on Raspberry Pi

> On 14-01-2016, at 5:51 AM, Jon Hylands <[hidden email]> wrote:
>
>
> Hi everyone,
>
> I'm trying to use the SerialPort class on my Raspberry pi 2, to access the UART on the pi.
>
> I've successfully accessed the port from python, using pyserial. On the pi, the port name is '/dev/ttyAMA0’.

The only thing I can offer is that Scratch finds a serial port as /dev/ttyAMA0 as well, implying that on at least one Pi it finds the same port that python does. I don’t think I have any devices that I could even try to connect to. Any suggestions for things that might be around the office?

I do faintly recall some discussions about Pi serial stuff and having to use the rasp-config utility but that was a long time ago and I don’t seem to have any emails referring to it.


tim
--
tim Rowledge; [hidden email]; http://www.rowledge.org/tim
Strange OpCodes: EOS: Erase Operating System

On Mon, Jan 18, 2016 at 7:38 AM, tim Rowledge <[hidden email]> wrote:
Maybe you could just loop back...
http://unix.stackexchange.com/questions/117037/how-to-send-data-to-a-serial-port-and-see-any-answer

On Mon, Jan 18, 2016 at 8:35 AM, Ben Coman <[hidden email]> wrote:
Whoops, sent too soon - just a potential problem...
http://unix.stackexchange.com/questions/42964/unexpected-results-testing-serial-loopback-using-echo-and-cat

Loopback with SoCat
http://myrobotlab.org/content/serial-terminal-loopbacks-linux

Hardware loopback
http://serial-lines.blogspot.com.au/2011/04/for-this-post-were-going-to-send-some.html

Toubleshooting...
http://www.ee.ryerson.ca/~phiscock/papers/serial.pdf

cheers -ben

Hi Jon,

it used to work exactly like this.

I have two methods from March 2015 to control a servo controller via RS232C. One is:
initSystem
    (self serialPortName: '/dev/ttyAMA0') ifNil: [0 halt "can't init serial port"].
    self getErrors
which calls:
serialPortName: aString
    "return nil if opening failed"
    ^serial openPort: aString
and in initialize I do:
initialize
    "super uses two SerialPorts, so no super initialize here"
    serial := SerialPort new.
    serial baudRate: 115200.
    serialCommand := serial.

No access to my Pi's I just copied this from a backup of the Squeak 4.5 image with the old VM which I have on my laptop. I haven't used this software since last October (youngest method stamp). So maybe one of the raspbian updates broke it or the new VM or image need different incantations. I didn't use sudo but missing access rights can also cause problems.

Cheers,

Herbert

So maybe you try on 4.5 and the old VM.

You don't need a device to test it - Serial doesn't require a second device if all you're doing is sending bytes.

The issue I'm having is when I try and open the port - that part is failing.

Tim, not sure if you have Scratch set up to access the underlying Squeak code, but if you do:

| serialPort |

serialPort := SerialPort new.

serialPort baudrate: 115200.

serialPort openPort: '/dev/ttyAMA0'.

serialPort inspect

the port instance variable in serialPort will be nil if it failed, and something else if it didn't fail.

Thanks,

Jon

On Sun, Jan 17, 2016 at 6:38 PM, tim Rowledge <[hidden email]> wrote:

> On 14-01-2016, at 5:51 AM, Jon Hylands <[hidden email]> wrote:
>
>
> Hi everyone,
>
> I'm trying to use the SerialPort class on my Raspberry pi 2, to access the UART on the pi.
>
> I've successfully accessed the port from python, using pyserial. On the pi, the port name is '/dev/ttyAMA0’.

The only thing I can offer is that Scratch finds a serial port as /dev/ttyAMA0 as well, implying that on at least one Pi it finds the same port that python does. I don’t think I have any devices that I could even try to connect to. Any suggestions for things that might be around the office?

I do faintly recall some discussions about Pi serial stuff and having to use the rasp-config utility but that was a long time ago and I don’t seem to have any emails referring to it.


tim
--
tim Rowledge; [hidden email]; http://www.rowledge.org/tim
Strange OpCodes: EOS: Erase Operating System

It’s probably well worth comparing platforms/unix/plugins/SerialPlugin/sqUnixSerial.c & platforms/unix/plugins/ScratchPlugin/unixSerialPort2Ops.c

tim
--
tim Rowledge; [hidden email]; http://www.rowledge.org/tim
Ornerythologists study bad tempered birds