user18546: I have the esp01 connected the serial port using a usb to ttl serial cable and also using the Arduino UNO as suggested in some tutorials. I can execute AT commands. But loading a sketch from Arduino IDE results in error messages show below. If anyone can help, it would be greatly appreciated. Note the error message: 

serialport_receive_C0: F0 instead of C0

Build options changed, rebuilding all

Sketch uses 219,211 bytes (50%) of program storage space. Maximum is 434,160 bytes.     Global variables use 31,416 bytes (38%) of dynamic memory, leaving 50,504 bytes for local variables. Maximum is 81,920 bytes.
      /Users/syedtariq/Library/Arduino15/packages/esp8266/tools/esptool/0.4.8/esptool -vv -cd ck -cb 115200 -cp /dev/cu.usbmodem14221 -ca 0x00000 -cf /var/folders/hx/m49nxmvn0799w816ct3tgsjm0000gp/T/build10f6b721887f9efd16f05460daf22810.tmp/Blink.ino.bin 
esptool v0.4.8 - (c) 2014 Ch. Klippel <ck@atelier-klippel.de>
setting board to ck
setting baudrate from 115200 to 115200
setting port from /dev/tty.usbserial to /dev/cu.usbmodem14221
setting address from 0x00000000 to 0x00000000
espcomm_upload_file
espcomm_upload_mem
opening port /dev/cu.usbmodem14221 at 115200
tcgetattr
tcsetattr
serial open
opening bootloader
resetting board
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: F0 instead of C0
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: F0 instead of C0
resetting board
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: FF instead of C0
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: F0 instead of C0
resetting board
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: F0 instead of C0
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: F0 instead of C0
warning: espcomm_sync failed
error: espcomm_open failed
error: espcomm_upload_mem failed


user81883: The problem is related to the Arduino Uno, seems that you haven’t bypassed the Arduino board (since you need to program the esp you should communicate directly with it).
To do this you need to wire the reset pin of Arduino to the ground (also the GPIO1 of esp should be connected to the ground in order to go in programming mode).

18546: <p>I have the esp01 connected the serial port using a usb to ttl serial cable and also using the Arduino UNO as suggested in some tutorials. I can execute AT commands. But loading a sketch from Arduino IDE results in error messages show below. If anyone can help, it would be greatly appreciated. Note the error message: </p>

<blockquote>
  <p>serialport_receive_C0: F0 instead of C0</p>
</blockquote>

<pre><code>Build options changed, rebuilding all

Sketch uses 219,211 bytes (50%) of program storage space. Maximum is 434,160 bytes.     Global variables use 31,416 bytes (38%) of dynamic memory, leaving 50,504 bytes for local variables. Maximum is 81,920 bytes.
      /Users/syedtariq/Library/Arduino15/packages/esp8266/tools/esptool/0.4.8/esptool -vv -cd ck -cb 115200 -cp /dev/cu.usbmodem14221 -ca 0x00000 -cf /var/folders/hx/m49nxmvn0799w816ct3tgsjm0000gp/T/build10f6b721887f9efd16f05460daf22810.tmp/Blink.ino.bin 
esptool v0.4.8 - (c) 2014 Ch. Klippel &lt;ck@atelier-klippel.de&gt;
setting board to ck
setting baudrate from 115200 to 115200
setting port from /dev/tty.usbserial to /dev/cu.usbmodem14221
setting address from 0x00000000 to 0x00000000
espcomm_upload_file
espcomm_upload_mem
opening port /dev/cu.usbmodem14221 at 115200
tcgetattr
tcsetattr
serial open
opening bootloader
resetting board
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: F0 instead of C0
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: F0 instead of C0
resetting board
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: FF instead of C0
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: F0 instead of C0
resetting board
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: F0 instead of C0
trying to connect
setting character timeout 0
done
setting character timeout 1
done
espcomm_send_command: sending command header
espcomm_send_command: sending command payload
serialport_receive_C0: F0 instead of C0
warning: espcomm_sync failed
error: espcomm_open failed
error: espcomm_upload_mem failed
</code></pre>
 81883: <p>The problem is related to the Arduino Uno, seems that you haven’t bypassed the Arduino board (since you need to program the esp you should communicate directly with it).
To do this you need to wire the reset pin of Arduino to the ground (also the GPIO1 of esp should be connected to the ground in order to go in programming mode).</p>
