LDDS75 with optional DS1820 -- not working

End Devices (Nodes) Dragino
1

Did anybody get the LDDS75 with optional DS1820 to work?

My setup:
Hardware version:LSN50 RS-485-UART-I2C V1.3
LDDS75 LoRaWAN Distance Sensor
Image Version: v1.1.4

I’m not able to get the DS1820 sensor to work with a LDDS75 running newest firmware.
I tried two DS1820 sensors, and yes I’m using a pullup resistor on its data-line.

According to manual it should work:
DS18B20 Temperature sensorThis is optional, user can connect external DS18B20 sensor to the +3.3v, 1-wire and GND pin. and this field will report temperature.
Section 2.3.4 in https://www.dragino.com/downloads/downloads/LoRa_End_Node/LDDS75/LoRaWAN_LDDS75_User%20Manual_v1.4.pdf

2

I double checked my two DS18B20:
Their address starts with 0x28 , so they are DS18B20 (and not a DS1820 or DS18S20))
…and they work fine when hooked to an Arduino using the same 5k pull-up resistor.

Reviewing the AT command manual also revealed nothing which could help …

Below the received data from TTN V3 , the two bytes which should contain temperature are 0x00

image

3

What did Dragino advise when you asked them/their forum?

4

Dragino sent response today.
Starting to work on issue with David (Dragino) .
Will post again once we have finalized results.

1 Like
5

Lots of alleged ds sensors (most of those on the hobby market, vs a true distributor) are fakes or test fails. They tend to work a bit but do things like respond more slowly than speccd. If you look around I think someone wrote a guide and either Arduino sketch or pi python thing that tries to identify actual real/fake types by their specific quirks of behavior.

A scope might help you see what’s going on with the node firmware’s attempts, but my guess is you need to either get a genuine sensor of the supported model or modify the firmware to work with what you have the way your Arduino test does.

Much of the accuracy issues in temperature sensing come not from the sensor itself, but from either the hosting electronics heating the sensor above ambient, or from the challenge if truly sampling environment conditions in one little epoxy blob that may see different airflow, radiant heating, etc than whatever you really want to know the temperature of. Room temperature sensing turns out to be hard.

6

Yes lots of fake ones, who supplies the real DS18B20 (Dallas Semiconductor now Maxim)?

Four of them (Fake ones) in one glass of water the spread is more than 1 degree C
image

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The DS18B20 sensor does not even get power at this point (when hooked up as directed in LDDS75 manual V1.4).

As I posted earlier : Working with Dragino support on this issue. Once we have a solution I’ll post it.

8

The problem has been found.

The LDDS75 comes in various hardware versions.
The DS1820 feature is supported starting with hardware version V1.3 (released Nov 2020)
The unit I purchased end of Jan 2021 was unfortunately V1.2 which will not work with a DS1820.
The current user manual (1.4) does currently not point this issue out.

To verify the hardware version you must look at the main board silk screen underneath the LoRa-card.
(The hardware version reported via AT-commands will not show you the correct version, but report V1.3 despite the board being V1.2)

hardwareversion1.2

2 Likes
9

Thanks for sharing the details - hopefully no one else will get caught out at a later date!