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19718: drivers/dht: busy wait reimplementation r=benpicco a=hugueslarrive ### Contribution description In PR #19674, I also provided quick and dirty fixes to restore functionality on esp8266 and enable operation on AVR. While reviewing PR #18591, it became apparent to me that this driver needed a refresh, particularly its migration to ztimer. The cause of the malfunction on esp8266 was that since the default switch to ztimer as the backend for xtimer, XTIMER_BACKOFF was no longer taken into account. Therefore, the correction I provided in PR #19674 simply made explicit what was previously done implicitly with xtimer and now needs to be done explicitly with ztimer (spinning instead of sleeping). Moreover, it was unnecessarily complex to measure the pulse duration in a busy-wait implementation, which required 2 calls to ztimer_now() and 32-bit operations expensive on 8-bit architecture. Instead, it is sufficient to read the state of the bus at the threshold moment. Finally, in practice, it is possible to reduce the read interval (down to less than 0.5s for DHT22) by "harassing" the DHT with start signals until it responds. This re-implementation brings the following improvements: - Many backports from `@maribu's` IRQ based implementation (#18591): - Use of ztimer - Use of errno.h - Use of a dht_data structure to pass arguments, to facilitate integration - Adaptation of the bit parsing technique to parse bits into the data array - Reintroduction of DHT11/DHT22 differentiation. - Separation of `dht_read()` steps into functions for better readability and the ability to share certain functions among different implementations - Sensor presence check in `dht_init()` - ~~Automatic adjustment to a minimum data hold time~~ - Default input mode changed to open drain (a pull-up resistor should be placed close to the output if necessary but not close to the input) - AVR support without platform-specific handling by avoiding ztimer_spin() and using the overflow of an 8-bit variable as a pre-timeout to minimize time-consuming ztimer_now() calls Regarding the changes in the start signal sequence and the removal of the `_reset()` function:  ~~In the previous implementation, there was an unnecessary spike at the beginning of the signal sequence, corresponding to START_HIGH_TIME. This spike has been removed in the re-implementation, as it is unnecessary. Instead, the MCU now simply pulls the signal low for START_LOW_TIME and then releases the bus, which is sufficient for initiating communication with the DHT sensor.~~ Actually, it is necessary to raise the bus level; otherwise, the _wait_for_level() called immediately after to check the response of the DHT may read the port before the signal level is raised, resulting in a false positive. Additionally, the previous implementation had an issue where the MCU switched back to output mode and went high immediately after reading the 40 bits of data. However, the DHT sensor was still transmitting 2 or 3 additional bytes of '0' at that point, causing a conflict. This issue has been resolved in the re-implementation:  ~~Regarding the optimization for AVR, I have performed measurements of `_wait_for_level()` until timeout (85 loops):~~ ~~- on esp8266-esp-12x: 264 µs, which is 3.11 µs per loop~~ ~~- on nucleo-f303k8: 319 µs, which is 3.75 µs per loop~~ ~~- on arduino-nano: 3608 µs, which is 42.45 µs per loop~~ ~~Duration measurements on the Arduino Nano:~~ 19737: dist/tools/openocd: start debug-server in background and wait r=benpicco a=fabian18 19746: buildsystem: Always expose CPU_RAM_BASE & SIZE flags r=benpicco a=Teufelchen1 ### Contribution description Hello 🐧 This moves the definition of `CPU_RAM_BASE/SIZE` from being only available in certain situation to be always available. Reason for change is to simplify common code in the cpu folder. In cooperation with `@benpicco` ### Testing procedure Passing CI ### Issues/PRs references First usage will be in the PMP driver. Although there is more code in RIOT that could be refactored to use these defines instead of hacks / hardcoded values. Co-authored-by: Hugues Larrive <hlarrive@pm.me> Co-authored-by: Fabian Hüßler <fabian.huessler@ml-pa.com> Co-authored-by: Teufelchen1 <bennet.blischke@outlook.com> |
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| bootloaders | ||
| core | ||
| cpu | ||
| dist | ||
| doc | ||
| drivers | ||
| examples | ||
| fuzzing | ||
| kconfigs | ||
| makefiles | ||
| pkg | ||
| sys | ||
| tests | ||
| .bandit | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .murdock | ||
| .murdock.yml | ||
| bors.toml | ||
| CITATION.cff | ||
| CODE_OF_CONDUCT.md | ||
| CODEOWNERS | ||
| CODING_CONVENTIONS_C++.md | ||
| CODING_CONVENTIONS.md | ||
| CONTRIBUTING.md | ||
| doc.txt | ||
| Kconfig | ||
| LICENSE | ||
| LOSTANDFOUND.md | ||
| MAINTAINING.md | ||
| Makefile | ||
| Makefile.base | ||
| Makefile.dep | ||
| Makefile.features | ||
| Makefile.include | ||
| README.md | ||
| release-notes.txt | ||
| SECURITY.md | ||
| SUBSYSTEMS.md | ||
| uncrustify-riot.cfg | ||
| Vagrantfile | ||
The friendly Operating System for IoT!
RIOT is a real-time multi-threading operating system that supports a range of devices that are typically found in the Internet of Things (IoT): 8-bit, 16-bit and 32-bit microcontrollers.
RIOT is based on the following design principles: energy-efficiency, real-time capabilities, small memory footprint, modularity, and uniform API access, independent of the underlying hardware (this API offers partial POSIX compliance).
RIOT is developed by an international open source community which is independent of specific vendors (e.g. similarly to the Linux community). RIOT is licensed with LGPLv2.1, a copyleft license which fosters indirect business models around the free open-source software platform provided by RIOT, e.g. it is possible to link closed-source code with the LGPL code.
FEATURES
RIOT provides features including, but not limited to:
- a preemptive, tickless scheduler with priorities
- flexible memory management
- high resolution, long-term timers
- MTD abstraction layer
- File System integration
- support 200+ boards based on AVR, MSP430, ESP8266, ESP32, RISC-V, ARM7 and ARM Cortex-M
- the native port allows to run RIOT as-is on Linux and BSD. Multiple instances of RIOT running on a single machine can also be interconnected via a simple virtual Ethernet bridge or via a simulated IEEE 802.15.4 network (ZEP)
- IPv6
- 6LoWPAN (RFC4944, RFC6282, and RFC6775)
- UDP
- RPL (storing mode, P2P mode)
- CoAP
- OTA updates via SUIT
- MQTT
- USB (device mode)
- Display / Touchscreen support
- CCN-Lite
- LoRaWAN
- UWB
- Bluetooth (BLE) via NimBLE
GETTING RIOT
The most convenient way to get RIOT is to clone it via Git
$ git clone https://github.com/RIOT-OS/RIOT
this will ensure that you get all the newest features and bug fixes with the caveat of an ever changing work environment.
If you prefer things more stable, you can download the source code of one of our quarter annual releases via Github as ZIP file or tarball. You can also checkout a release in a cloned Git repository using
$ git pull --tags
$ git checkout <YYYY.MM>
For more details on our release cycle, check our documentation.
GETTING STARTED
- You want to start the RIOT? Just follow our quickstart guide or try this tutorial. For specific toolchain installation, follow instructions in the getting started page.
- The RIOT API itself can be built from the code using doxygen. The latest version of the documentation is uploaded daily to doc.riot-os.org.
FORUM
Do you have a question, want to discuss a new feature, or just want to present your latest project using RIOT? Come over to our forum and post to your hearts content.
CONTRIBUTE
To contribute something to RIOT, please refer to our contributing document.
MAILING LISTS
- RIOT commits: commits@riot-os.org
- Github notifications: notifications@riot-os.org
LICENSE
- Most of the code developed by the RIOT community is licensed under the GNU Lesser General Public License (LGPL) version 2.1 as published by the Free Software Foundation.
- Some external sources, especially files developed by SICS are published under a separate license.
All code files contain licensing information.
For more information, see the RIOT website: