I'm using an ESP8266 with Micropython to communicate with a serial terminal using Putty. Using escape sequences like referenced in these questions:
Read ANSI escape from terminal
How do I determine size of ANSI terminal?
List of escape sequences https://vt100.net/docs/vt100-ug/chapter3.html
I am trying to read back an escape sequence that is a reply to find the cursor position.
I can see the response in the terminal, but I need to capture it so I can parse it. I'm familiar with Python, but a complete noob with Micropython and the ESP8266 (ESP01). I'm using the webrepl to upload the code. I saw this and I'm not sure if it's related: https://forum.micropython.org/viewtopic.php?t=5359
I've tried running my code without webrepl connected, but it still didn't work.
What am I doing wrong, how can I capture the response?
Depending on the terminal size, the response should be something like below, the stuff before the ; will not be visible.
^[[45;157R
#import esp
import network
import machine
from machine import UART
uart = UART(0, 115200)
x=uart.write("\033[500;500H\033[6n")
if uart.any():
print(":> ", uart.read())
EDIT: Tried example from this link https://forum.micropython.org/viewtopic.php?t=5359#p30867
No luck with that either (yes, I know it's blocking). Here if I type the letter 'R', it drops out of the loop, but it's not catching the output from the escape sequence.
from machine import UART
import machine
import network
import uos
uos.dupterm(None, 1)
uart = UART(0, 115200)
charbuf = None
uart.write("\033[500;500H\033[6n")
while charbuf != b"R":
if uart.any():
charbuf = uart.read()
uart.write(charbuf)
uos.dupterm(UART(0, 115200), 1)
Solving this was a nightmare, the WebRepl console replication has been the bane of my existence and probably many others. I tried multiple read() methods and they all failed.
uart.read()
sys.stdin.read()
sys.stdin.buffer.read()
Those were in combination of enabling/disabling the console duplication for webrepl.
The incantation that finally worked for me is below. See inline comments for more details.
import machine
import network
#import sys
import uos
from machine import UART
uos.dupterm(None, 1) # Disable console duplication for Webrepl
uart = UART(0, 115200, timeout=100, timeout_char=100) #Instantiate uart, increase timeout for good measure
uart.write("\033[2J\033[1;1f") # Clear screen
uart.write("\033[500;500H\033[6n") # Move cursor to bottom right, send query.
# Wait for uart to collect response. This will block further execution until we get a reply.
while True:
if uart.any() != 0:
break
uos.dupterm(UART(0, 115200), 1) # Re-enable console redirection so print() will work
# Read the uart buffer with response, convert from binary to string, replace ESC character.
# First ^ gets eaten somewhere!
buf = str(uart.read(), 'UTF-8').replace('\x1b', '^^[')
if len(buf) > 0: # If response isn't empty, print buffer
print(buf)
This is the Output:
^[[43;157R
Related
This question came up into my mind when I was thinking about ways of server logging yesterday.
Normally, we open a terminal connected to local computer or remote server, run an executable, and print (printf, cout) some debug/log information in the terminal.
But for those processes/executables/scripts running on the server which are not connected to a terminal, what are the standard input and output?
For example:
Suppose I have a crontab task, running a program on the server many times a day. If I write something like cout << "blablabla" << endl; in the program. What's gonna happen? Where those output will flow into?
Another example I came up and wanted to know is, if I write a CGI program (use C or C++) for let's say a Apache web server, what is the standard input and output of my CGI program ? (According to this C++ CGI tutorial, I guess the standard input and output of the CGI program are in some ways redirected to the Apache server. Because it's using cout to output the html contents, not by return. )
I've read this What is “standard input”? before asking, which told me standard input isn't necessary to be tied to keyboard while standard output isn't necessary to be tied to a terminal/console/screen.
OS is Linux.
The standard input and standard output (and standard error) streams can point to basically any I/O device. This is commonly a terminal, but it can also be a file, a pipe, a network socket, a printer, etc. What exactly those streams direct their I/O to is usually determined by the process that launches your process, be that a shell or a daemon like cron or apache, but a process can redirect those streams itself it it would like.
I'll use Linux as an example, but the concepts are similar on most other OSes. On Linux, the standard input and standard output stream are represented by file descriptors 0 and 1. The macros STDIN_FILENO and STDOUT_FILENO are just for convenience and clarity. A file descriptor is just a number that matches up to some file description that the OS kernel maintains that tells it how to write to that device. That means that from a user-space process's perspective, you write to pretty much anything the same way: write(some_file_descriptor, some_string, some_string_length) (higher-level I/O functions like printf or cout are just wrappers around one or more calls to write). To the process, it doesn't matter what type of device some_file_descriptor represents. The OS kernel will figure that out for you and pass your data to the appropriate device driver.
The standard way to launch a new process is to call fork to duplicate the parent process, and then later to call one of the exec family of functions in the child process to start executing some new program. In between, it will often close the standard streams it inherited from its parent and open new ones to redirect the child process's output somewhere new. For instance, to have the child pipe its output back to the parent, you could do something like this in C++:
int main()
{
// create a pipe for the child process to use for its
// standard output stream
int pipefds[2];
pipe(pipefds);
// spawn a child process that's a copy of this process
pid_t pid = fork();
if (pid == 0)
{
// we're now in the child process
// we won't be reading from this pipe, so close its read end
close(pipefds[0]);
// we won't be reading anything
close(STDIN_FILENO);
// close the stdout stream we inherited from our parent
close(STDOUT_FILENO);
// make stdout's file descriptor refer to the write end of our pipe
dup2(pipefds[1], STDOUT_FILENO);
// we don't need the old file descriptor anymore.
// stdout points to this pipe now
close(pipefds[1]);
// replace this process's code with another program
execlp("ls", "ls", nullptr);
} else {
// we're still in the parent process
// we won't be writing to this pipe, so close its write end
close(pipefds[1]);
// now we can read from the pipe that the
// child is using for its standard output stream
std::string read_from_child;
ssize_t count;
constexpr size_t BUF_SIZE = 100;
char buf[BUF_SIZE];
while((count = read(pipefds[0], buf, BUF_SIZE)) > 0) {
std::cout << "Read " << count << " bytes from child process\n";
read_from_child.append(buf, count);
}
std::cout << "Read output from child:\n" << read_from_child << '\n';
return EXIT_SUCCESS;
}
}
Note: I've omitted error handling for clarity
This example creates a child process and redirects its output to a pipe. The program run in the child process (ls) can treat the standard output stream just as it would if it were referencing a terminal (though ls changes some behaviors if it detects its standard output isn't a terminal).
This sort of redirection can also be done from a terminal. When you run a command you can use the redirection operators to tell your shell to redirect that commands standard streams to some other location than the terminal. For instance, here's a convoluted way to copy a file from one machine to another using an sh-like shell:
gzip < some_file | ssh some_server 'zcat > some_file'
This does the following:
create a pipe
run gzip redirecting its standard input stream to read from "some_file" and redirecting its standard output stream to write to the pipe
run ssh and redirect its standard input stream to read from the pipe
on the server, run zcat with its standard input redirected from the data read from the ssh connection and its standard output redirected to write to "some_file"
I created a small project on ESP32 with nodemcu firmware which communicates with a sim808 module via uart2. My problem is, that the response from uart many times is not easy for interpretation within lua and nodemcu.
Here a short example of my code:
uart.on(2, "data", "\r", function(data)
print("Checking UART: "..data)
if (string.match(data, "RING")) then
print("Someone rings")
elseif (string.match(data, "CLIP:")) then
print("Phone number: "..data) -- shortened, I know that the whole line will appear
elseif (string.match(data, 'NO CARRIER')) then
print("Ring canceled")
else
print("Dont understand")
end
end, 0)
In above case - RING and NO CARRIER inputs are matching correctly and the proper info is given.
I have also many other such searchings which works. But when I look for the phone no (+CLIP:...) the code is ignorig this input, however I see it on the serial console output:
Checking UART:
Dont understand
Checking UART:
+CLIP: "+xxxxxxxxxxx",145,"",0,"",0
Checking UART:
Dont understand
I see also that this specific answer has new line character after and the loop goes again with no chars, maybe that's why the code can't find it, but the build in function uart.on should check every line (\r).
The same issue when I get some bluetooth command, also can't put it to a variable.
I installed ROS melodic version in Ubuntu 18.04.
I'm running a rosbag in the background to mock cameras in messages rostopics.
I set the camera names in rosparams and iterated through it to capture each camera topics.
I'm using message_filter ApproximateTimeSynchronizer to get time synchronized data as mentioned in the official documentation,
http://wiki.ros.org/message_filters
But most of the time the callback function to ApproximateTimeSynchronizer is not being called/is having delay. The code snippet I'm using is given below:
What am I doing wrong here?
def camera_callback(*args):
pass # Other logic comes here
rospy.init_node('my_listener', anonymous=True)
camera_object_data = []
for camera_name in rospy.get_param('/my/cameras'):
camera_object_data.append(message_filters.Subscriber(
'/{}/hd/camera_info'.format(camera_name), CameraInfo))
camera_object_data.append(message_filters.Subscriber(
'/{}/hd/image_color_rect'.format(camera_name), Image))
camera_object_data.append(message_filters.Subscriber(
'/{}/qhd/image_depth_rect'.format(camera_name), Image))
camera_object_data.append(message_filters.Subscriber(
'/{}/qhd/points'.format(camera_name), PointCloud2)
topic_list = [filter_obj for filter_obj in camera_object_data]
ts = message_filters.ApproximateTimeSynchronizer(topic_list, 10, 1, allow_headerless=True)
ts.registerCallback(camera_callback)
rospy.spin()
Looking at your code, it seems correct. There is, however, a trouble with perhaps bad timestamps and ergo this synchronizer as well, see http://wiki.ros.org/message_filters/ApproximateTime for algorithm assumptions.
My recommendation is to write a corresponding node that publishes empty versions of these four msgs all at the same time. If it's still not working in this perfect scenario, there is an issue with the code above. If it is working just fine, then you need to pay attention to the headers.
Given that you have it as a bag file, you can step through the msgs on the command line and observe the timestamps as well. (Can also step within python).
$ rosbag play --pause recorded1.bag # step through msgs by pressing 's'
On time-noisy msgs with small payloads, I've just written a node to listen to all these msgs, and republish them all with the latest time found on any of them (for sync'd logging to csv). Not optimal, but it should reveal where the issue lies.
I'm using LabVIEW and its VISA capabilities to control a Keithley 2635A source meter. Whenever I try to identify the device, it works just fine, both in reading and writing.
viWRITE(*IDN?) /* VISA subVI to send the command to the machine */
viREAD /* VISA subVI to read output */
However, as soon as I set the voltage (or current), it does so. Then I send the command to perform a measurement, but I'm not able to read that data, with the error
VISA: (Hex 0xBFFF0015) Timeout expired before operation completed.
After that, I can not read the *IDN? output either anymore.
The source meter is connected to the PC via a National Instrument GPIB-USB-HS adaptor.
EDIT: I forgot to add, this happens in the VISA Interactive Control program as well.
Ok, apparently the documentation is not very clear. What the smua.measure.X() (where X is the needed parameter) command does is, of course, writing the measurement outcome on a buffer. In order to read that buffer, however, the simple viREAD[] is not sufficient.
So basically the answer was to simply add a print command: this way I have
viWRITE[print(smua.measure.X())];
viREAD[]
And I don't have the error anymore. Not sure why such a command is needed, but that's that. Thank you all for your time answering me.
As #Tom Blodget mentions in the comments, the machine may not have any response to read after you set the voltage. The *IDN? string is both command and query. That is, you will write the command *IDN? and read the result. Some commands do not have any response to read. Here's a quick test to see if you should be reading from the instrument. The following code is in python; I made up the GPIB command to set voltage.
sm = SourceMonitor()
# Prints out IDN
sm.query('*IDN?')
# Prints out current voltage (change this to your actual command)
sm.query('SOUR:VOLT?')
# Set a new voltage
sm.write('SOUR:VOLT 1V')
# Read the new voltage
sm.query('SOUR:VOLT?')
Note that question-marked GPIB commands and the query are used when you expect to get a response from the instrument. The instrument won't give a response for the write command. Query is a combination of write(...) and read(...). If you're using LabView, you may have to write the write and read separately.
If you need verification that the machine received your instruction and acted on it, most instruments have the following common commands:
*OPC? query to see if the operation is complete
SYST:ERR? query to see if any error was generated
Add a question mark ? to the end of the GPIB command used to set the voltage
I want read on stdout to be non-blocking. I was using the newlib-lpc library in WINarm to do this. But even though it is set as non-Blocking, the code stops at read every time and waits for a character to be received.
Here is my read line:
read(fileno(stdout), &inchar, 1);
Here is the code to set stdout to non-blocking using newlib-lpc
blocking=BLOCKING_IO_NO;
ioctl( fileno(stdout), BLOCKING_SETUP, &blocking);
When that didn't work, I decided to forget using the library and do it myself with this line
fcntl(fileno(stdout), F_SETFL,fcntl(fileno(stdout), F_GETFL) |O_NONBLOCK);
But that didn't work either.
Could anyone give me some advice?
Thanks!
edit:
Someone asked if I really meant stdout. Yes, I am resurrecting some old code, and the stdout has been set as the socket for UART communication between my board and the computer.
sp.baud = 115200uL;
sp.length = UART_WORD_LEN_8;
sp.parity = UART_PARITY_NONE;
sp.stop = UART_STOP_BITS_1;
ioctl( fileno(stdout), UART_SETUP, &sp);
irq.FIQ = 0;
irq.pri = (INT_PRIORITY)10;
ioctl( fileno(stdout), INTERRUPT_SETUP, &irq);
edit2: They used stdout this way so that printf works. When it tries to print to stdout, it gets redirected to the UART serial stream.
edit3: The error I get when calling
ioctl( fileno(stdout), BLOCKING_SETUP, &blocking);
is
errno88 function not implemented