2020-05-19 17:26:00, 修改于2020-05-20 15:54:09
Objective and Rationale
This is the author's second article about the ESP8266 integrated circuit, a relatively new chip comprising a full-featured 32-bit RISC |¨¬C and also a built-in 802.11 b/g/n Wi-Fi circuit. The first article described using the Arduino IDE to program the ESP8266, and contains some important background information that will not be repeated here. If you haven't read it, please do.
There is no shortage of information on the Web about the 8266; in fact, there may be too much...of the wrong type. The developers of the IC, Espressif, have apparently chosen to not only outsource manufacturing, but also to avoid being directly involved in the line of ESP modules that utilize the ESP8266 chip. Instead, they offer information and support services via a forum for those along with the patience and persistence to search the maze. Adding to the confusion is the existence of another forum that, despite being named esp8266.com, doesn't seem to be operated by Espressif. In addition, there is a plethora of resellers, video bloggers, and writers that also offer information that runs the gamut from good to confusing to totally wrong.
ESP modules are available from a variety of sources, and the firmware contained in the ESP8266 chips on the modules is almost always outdated and often of questionable origin. The firmware "updates" and tools that are available from these same sources are also sometimes suspect. Consequently, it is the aim of this article to document a procedure for downloading the latest available firmware directly from Espressif and installing it on an ESP8266 using the flash tool provided by Espressif.
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In order to update the firmware on any ESP8266, it is necessary to have it properly powered and connected to a PC. In addition, a means of resetting the IC and putting it in the download mode must be provided. The schematic diagram and photograph below show the recommended setup; note that the wire colors in the schematic correspond to the wire colors in the photograph. As you see, it is based on an ESP-01 module, but the same connections will work with other modules so long as the same ESP8266 I/Os are used as shown in the schematic diagram. For additional details, see this article.
Editor's note: A more reliable flashing circuit is available here, and should be utilised instead of the circuit described in this article.
PuTTY Terminal Program
Once the hardware setup is complete, the next step is to power up the ESP8266 and attempt to communicate with it. A simple terminal program is required and the following procedure takes advantage of PuTTY, a free program available here. You can use another terminal program, but you will have to make allowances for any differences between it and PuTTY.
Open PuTTY, and click the Serial radio button. Enter the COM port number (which must be less than 10) and the baud rate (which will most likely be 115200 or 9600.)
In the small Saved Sessions window, enter ESP8266, and click the Save button. The PuTTY window should be similar to the picture below.
Click the Open button, as well as a PuTTY terminal session window should open.
Enable Caps Lock on your PC, and type AT, but don't press Enter. You should see AT in the PuTTY terminal window. If you don't, you may have selected the wrong COM port or the wrong baud rate. Close PuTTY and start again at the top of this section. The permissible baud rates are: 9600, 19200, 38400, 74880, 115200, 230400, 460800, and 921600; try each one in turn until you find the one that works.
When you see AT in the PuTTY terminal window, while holding the Ctrl key down, press the M key followed by the J key. Release the Ctrl key. You should see OK in the PuTTY terminal window as shown in the picture below.