PPP: Add burst of AT commands to lock autobaudrate on begin#12314
PPP: Add burst of AT commands to lock autobaudrate on begin#12314gonzabrusco wants to merge 1 commit intoespressif:masterfrom
Conversation
👋 Hello gonzabrusco, we appreciate your contribution to this project! 📘 Please review the project's Contributions Guide for key guidelines on code, documentation, testing, and more. 🖊️ Please also make sure you have read and signed the Contributor License Agreement for this project. Click to see more instructions ...
Review and merge process you can expect ...
|
Memory usage test (comparing PR against master branch)The table below shows the summary of memory usage change (decrease - increase) in bytes and percentage for each target.
Click to expand the detailed deltas report [usage change in BYTES]
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Test Results 90 files 90 suites 35m 28s ⏱️ Results for commit 57fe36d. |
| // Send burst of AT to lock auto baurate on modem | ||
| for (int i = 0; i < 50; i++) { | ||
| esp_modem_at(_dce, "AT", NULL, 10); | ||
| } |
There was a problem hiding this comment.
IMO this should be only enabled if an argument of the constructor is set. @me-no-dev What do you think ?
There was a problem hiding this comment.
@lucasssvaz Just to add a data point: sending a short burst of "AT" commands is safe and has no side effects on modems that do not rely on autobaud.
In practice, this acts as a no-op for fixed-baud devices while greatly improving initialization reliability for autobaud-based modems, so I don’t think it needs to be gated behind an additional constructor option.
|
Hi, just an afterthought. In my implementation, the modem reset is handled externally and not delegated to PPP.begin(). In the current begin() code path, when a reset pin is configured, the module is reset and the code waits only 100 ms before attempting to synchronize. Even with the added AT burst introduced in this PR, this delay is likely insufficient. According to the SIM7000 datasheet, the minimum boot time after reset is approximately 4.5 seconds. I believe the code should wait longer before attempting to communicate with the modem in order to avoid premature sync failures. If you agree with this approach, I can add a longer delay after issuing the reset command in this same PR. 
|
2 participants
Description of Change
This Pull Request improves the robustness of PPPClass::begin() when used with cellular modems that boot in autobaud mode, such as SIMCom modules.
After a power-on reset, these modems often require multiple "AT\r" commands before they can lock onto the host UART baud rate. The current implementation attempts to synchronize immediately using esp_modem_sync(), which may fail if the modem is still determining the baud rate, leading to unnecessary retries and mode switching.
This change introduces a short burst of "AT\r" commands before calling esp_modem_sync(), allowing the modem to reliably lock the baud rate first. In practice, this significantly improves synchronization reliability without affecting modems that do not use autobaud.
Test Scenarios
I tested this change on a custom ESP32-based board equipped with a SIM7070 modem. Using a logic analyzer on the UART interface, I verified that the added AT command burst improves baud-rate locking and results in a more reliable initialization sequence.