Capture ANSI escape sequence response using Micropython ESP8266

Question

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)

score 1 · Answer 1 · answered Apr 06 '21 at 01:14

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

Capture ANSI escape sequence response using Micropython ESP8266

1 Answers1