Onewire search fails for devices with different bit 0 (IEC-83) #298
Description
Answers checklist.
- I have read the component documentation ESP-IDF Components and the issue is not addressed there.
- I am using target and esp-idf version as defined in component's idf_component.yml
- I have searched the issue tracker for a similar issue and not found any related issue.
Which component are you using? If you choose Other, provide details in More Information.
onewire_bus
ESP-IDF version.
5.1.2
Development Kit.
ESP32-S3-DevKitC
Used Component version.
1.0.1
More Information.
onewire_device_iter_get_next() fails if the discrepancy occurs on bit 0. For multiple devices of the same family, this does not happen, but in my case I have a DS2408 and a MAX31820(same as ds18B20). At the beginning of the search (line69), last_zero is set to 0, but this is also used to test for the last device detected (line 111). So, it there is a real discrepancy at bit 0, the search takes the '1' direction, and then terminates thinking it has discovered all devices. The App Note referenced sets last_zero = 0, but uses bit_id = 1 as the start condition -- this implementation uses rom_bit_index which starts at 0.
This project is also for the esp32 and uses a bit_id that starts at 1: https://github.com/SuperHouse/esp-open-rtos/blob/master/extras/onewire/onewire.c I have not verified it works, but I am going to implement something similar. It is probably as simple as starting rom_bit_index at 1, and then dealing with all the -1s necessary to fix rom_bit_mask and rom_byte_index etc.