Honeywell Evotherm HR92WE teardown

After some fiddling with a soldering iron, I removed all components. Here is my take on the board layout of the Honeywell HR92 unit.

During my quest for the CC1101 signals I did find the CSn, SCLK, SI, SO, GDO0 and GDO2. That makes it possible to do evesdropping on the device. All the wireless setup commands to the CC1101 can be watched and it is possible to relate the commands of this specific unit to the RF commands going out.

Also I have troubles finding a CC1101 board which runs on 868 MHz. So I can also use one HR92 unit and use it’s radio module to send data out. When I keep the reset signal of the Atmel microcontroller active, I can assume I could control the CC1101 from another microcontroller.

Devices in the EvoHome eco system:
HR92 (Digital Thermostatic Head)
HGI (Honeywell HGI interface)
HCF82
DTS92
T87RF
BDR91 (Relais BDR91 RF Module, switches up to 5 amps)

Some very interesting projects are:
https://github.com/ghoti57/evofw3?
https://indalo-tech.onlineweb.shop/SSM-D/p7844707_21129532.aspx
Ebay: nanoCUL USB-stick FTDI CC1101 868MHz FW 1.67 FHEM iobroker CCU / CCU2 CUL 868 + adapter

Talking about the Evofw3, why not just have a look what is needed there. First we need a CC1101 868 MHz board. My new facebook friend Eymert ordered a complete SSM-D (or SSM) module from from Indalo-tech. During that period he also ordered a couple of CC1101 868 MHz boards, probably from Ali. Eymert was so kind to send the units to me at cost price. This probably saves me 5 weeks of time. The CC1101 boards arrived at my door the next day. Thanks again Eymert for that.

I could not find a page describing the pin layout, so I just pixeled it in. Also I added a SMA connector bcos, I don’t know, it should be better? The provided antenna could do the job perfectly, but I need to do some testing to compare the performance between both.

The SSM-D module, which is quite popular, has a atmega32u4 which uses a HW Uart. So I went to Tinytronics (again) to get me one RobotDyn Micro – ATmega32U4 (or maybe I got two).

Now I also need the pin-assignment from controller to radio chip. For some inspiration I went to the Github pages and found the author of the project giving a comment on this subject. To be sure this does not get lost, here is a summary of the comment:
ghoti57 has commented on Mar 18

Firstly - have you looked at the README for the firmware?
Are you using the custom evofw3_avr board definitions?
You cannot build evofw3 with the standard Arduino board definitions.

OK assuming you're doing this....

The reason there is no definite answer is that evofw3 can be made to run on a number of avr platforms connected to a cc1101.
The problem is that many of the off-the-shelf packages make the connections in different ways.

The options in the evofw3_avr board options select one of the combinations I've seen or have had reported.
The options are actually controlled from evofw3_avr:boards.txt
This file specifies the values for GDO0, GDO2 and CCSEL which control xxx_pins.h

The following options are currently supported

Note the code DOES NOT use Arduino pin numbers - these are the avr pin identifiers and these are the values specified in xxx_pins.h

atmega328p
MOSI-B3 MISO-B4 SCK-B5 CSN-B2
nano: GDO0-INT1(D3) GDO2-INT0(D2)
pro: GDO0-INT0(D2) GDO2-INT1(D3)

atmega32u4
MOSI-B2 MISO-B3 SCK-B1
GDO0-TXD1(D3) GDO2-RXD1(D2)
ProMicro: CSN-B6
SHA: CSN-B0

If you've got an off the shelf package then one of these will probably work.
If you're making your own from components then, depending which processor you have, I'd go for the either atmega328p:nano or atmega32u4:ProMicro as they're the most common options.

Note:
atmega328p systems MUST have a 16MHz clock - it won't run on 8MHz.
atmega32u4 systems will run on an 8Mhz system.


So I took a piece of DuPont cable with rainbow colors, and clipped of the connectors at one side and soldered this to the CC1101 board.

Based on the comment from ghoti57 (Peter Price), I have connected everything together. Now hope it will work . ..

After measuring the components I came up with this list: