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Commit9d82ebe

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Add example for using ESP.rebootIntoUartDownloadMode() (#7897)
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/*
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Example of Booting into UART Download using `ESP.rebootIntoUartDownloadMode()`
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Two methods are presented for starting UART Boot Mode.
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1) From `loop()` call the function `proxyEspSync()`, which peeks for a SLIP
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frame marker. Then when present, look for an esptool ESP_SYNC packet on
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the Serial port.
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2) A simple hotkey of 'D'.
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After either of these, `ESP.rebootIntoUartDownloadMode()` is called to place
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the ESP8266 into UART Flash program mode.
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For a quick test to confirm the ESP8266 is responding to esptool.py,
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use this command:
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esptool.py --chip esp8266 --before no_reset --after soft_reset flash_id
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Note with these methods a hard reset is not done, and the esptool.py may not
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detect and report the correct Crystal frequency for the ESP Module. If you
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need that info, it needs to be gathered after a Power-On or Hard Reset.
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*/
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#include<Arduino.h>
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#include<ESP8266WiFi.h>
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////////////////////////////////////////////////////////////////////////////////
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//
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// Check Serial Receive for ESP_SYNC slip packet from esptool.py
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//
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// If you are already using Serial input for command input, the character '\xC0'
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// is not available. We must reserve its use for the SLIP Frame Marker. I am not
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// sure which languages if any, would pose a problem. For the non-English
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// languages check your character set values to be sure it is not an issue. If
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// it is an issue, you will not be able to use this method as presented. The
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// '\xC0' character is defined by the SLIP protocol and cannot be changed.
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// If your needs require it, you can add logic to loop() for setting and
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// clearing uartDownloadEnable. For example, you could add a push button to a
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// GPIO pin and monitor for a 5-second press. Then, set uartDownloadEnable to
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// true. In addition to that, you could also define a time-to-live for that
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// state and clear it after it elapses.
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//
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// Change this to false if you do not want ESP_SYNC monitor always on.
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bool uartDownloadEnable =true;
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// Buffer size to receive an ESP_SYNC packet into, larger than the expected
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// ESP_SYNC packet length.
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constexprsize_t pktBufSz =64;
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// Enough time to receive 115 bytes at 115200bps.
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// More than enough to finish receiving an ESP_SYNC packet.
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constexprsize_tkSyncTimeoutMs =10;
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// The SLIP Frame end character, which is also used to start a frame.
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constexprchar slipFrameMarker ='\xC0';
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// General packet format:
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// <0xC0><cmd><payload length><32 bit cksum><payload data ...><0xC0>
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// Slip packet for ESP_SYNC, minus the frame markers ('\xC0') captured from
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// esptool using the `--trace` option.
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constchar syncPkt[] PROGMEM =
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"\x00\x08\x24\x00\x00\x00\x00\x00\x07\x07\x12\x20"
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"UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU";
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constexprsize_t syncPktSz =sizeof(syncPkt) -1;// Don't compare zero terminator char
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//
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// Use the discovery of an ESP_SYNC packet, to trigger calling UART Download
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// Mode. At entry we expect the Serial FIFO to start with the byte following
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// the slipFrameMarker.
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//
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voidproxyEspSync() {
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if (!uartDownloadEnable) {
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return;
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}
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byte buf[pktBufSz];
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// If it is an ESP_SYNC packet, it will not take long for readBytesUntil() to
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// complete.
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Serial.setTimeout(kSyncTimeoutMs);
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int len = Serial.readBytesUntil(slipFrameMarker, buf, pktBufSz);
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// To avoid a false trigger, only start UART Download Mode when we get an
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// exact match to the captured esptool ESP_SYNC packet.
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if (syncPktSz == len &&0 ==memcmp_P(buf, syncPkt, len)) {
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ESP.rebootIntoUartDownloadMode();
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// Does not return
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}
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// Assume RX FIFO data is garbled and flush all RX data.
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while (0 <= Serial.read()) {}// Clear FIFO
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// If your Serial requirements need a specific timeout value, you would
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// restore those here.
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}
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//
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////////////////////////////////////////////////////////////////////////////////
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voidpreinit() {
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// (no C++ in function)
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// disable wifi
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ESP8266WiFiClass::preinitWiFiOff();
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}
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voidsetup() {
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// For `proxyEspSync()` to work, the Serial.begin() speed needs to be
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// 115200bps. This is the data rate used by esptool.py. It expects the Boot
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// ROM to use its "auto-baud" feature to match up. Since `proxyEspSync()` is
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// acting as a proxy we must use 115200.
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//
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// If on the Arduino IDE Tools menu you use "Upload Speeds" above 115200, it
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// will work. When esptool.py is run with the `--baud BAUD` option specified
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// above 115200, initial communication with the ESP8266 is done at 115200bps.
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// Once esptool.py has synchronize with the ESP8266 and downloaded a short
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// stub, then both devices shift their UART speeds to the command line value.
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Serial.begin(115200);
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Serial.println(F(
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"\r\n\r\n"
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"Boot UART Download Demo - initialization started.\r\n"
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"\r\n"
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"For a quick test to see the UART Download work,\r\n"
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"stop your serial terminal APP and run:\r\n"
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" esptool.py --chip esp8266 --before no_reset --after soft_reset flash_id\r\n"));
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// ...
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}
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voidcmdLoop(Print& oStream,int key) {
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switch (key) {
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case'e':
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oStream.println(F("Enable monitor for detecting ESP_SYNC from esptool.py"));
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uartDownloadEnable =true;
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break;
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case'D':
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// This option would be prone to false triggering. It is here for DEMO
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// purposes and debugging.
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oStream.println(F("Boot into UART download mode ..."));
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oStream.flush();
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ESP.rebootIntoUartDownloadMode();
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break;
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case'R':
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oStream.println(F("Restart ..."));
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oStream.flush();
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ESP.restart();
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break;
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// ...
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case'?':
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oStream.println(F("\r\nHot key help:"));
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if (!uartDownloadEnable) {
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oStream.println(F(" e - Enable monitor for detecting ESP_SYNC from esptool.py"));
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}
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oStream.println(F(" D - Boot into UART download mode"));
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oStream.println(F(" R - Restart"));
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oStream.println(F(" ? - This help message\r\n"));
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break;
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default:
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break;
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}
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oStream.println();
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}
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voidloop() {
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// In this example, we can have Serial data from a user keystroke for our
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// command loop or the esptool trying to SYNC up for flashing. If the
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// character matches the Slip Frame Marker (the 1st byte of the SYNC packet),
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// we intercept it and call our ESP_SYNC proxy to complete the verification
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// and reboot into the UART Downloader. Otherwise, process the keystroke as
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// normal.
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if (0 < Serial.available()) {
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int keyPress = Serial.read();
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if (slipFrameMarker == keyPress) {
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proxyEspSync();
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}else {
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cmdLoop(Serial, keyPress);
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}
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}
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// ...
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}

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