hello!!! Finally got my modules from jlcpcb, almost complete, just attiny soldered carefully by me. Programing with arduino ISP, went well (fuses ok), connected RX/TX lines (wires should be direct or crossed ??) Green led on cell module is solid when battery is connected. No communication with controller module.
Unfortunately when I try to reflash is says “avrdude: Device signature = 0x000000 (retrying)”
I’ve managed to upload cell module code correctly, now it boots, blinks green, then blue two times.
Still no communication with controller though. 
After flashing and wiring additionall module I’ve connected debug and receive…
[…]
S:90/1/144=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 =A19D/Q:1
S:90/3/145=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 =F3D2/Q:0
S:80/1/146=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 =3DA4/Q:3
S:80/3/147=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 =6FEB/Q:2
S:90/1/148=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 =50E7/Q:1
S:90/3/149=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 =2A8/Q:0
S:80/1/14A=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 =CCDE/Q:3
S:80/3/14B=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 =9E91/Q:2
S:90/1/14C=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 =31/Q:1
[…]
Both modules don’t blink with green led, one of them blinks 2x blue from time to time.
Looks like you have done well so far. The modules will blink blue when they have no comms for 8 seconds, thats normal.
It also looks like the controller is working and trying to send out messages. Can you loop the TX and RX connections together on the controller. You should see “ignored request” errors in the web pages.
I suspect this is a simple case of the JST cables not being straight through. If you have brought cables from ebay/aliexpress then they are normally crossed over.
Thanks for a prompt response!
yeah, tried with loopback on TX/RX and I can see ignored request errors, so my controller sends messages.
Tried also with v. short cables, twisted, swapped p1/p2 (my jst’s are connected directly 1-1,2-2).
Is there anything more I can check ?
Do any of the green LEDs on the modules flash when the controller transmits?
It could be a short or bad solder joint on the JST connectors or on the attiny.
Try using the burn fuse option on the modules from platform Io.
Yay!!! Works, cell module is detected.
it was actually this one - I don’t know how it happened, but I’ve set wrong
lfuse to -Ulfuse:w:0b11111100:m (copied accidentally from 4.30 with external clock).
Now I do understand why few modules I’ve assembled and flashed don’t react on anything. Is there a way to recover/reset this flag on a module that is not recognised anymore ?
Oh, you didn’t did you!!
Recovery is possible but a pain. You need to attach an external crystal and 2 capacitors to the xtal pins on each tiny841, and reprogram the correct fuses.
yes, I did… 
lucky me.
still have plenty of spare parts to continue. 
everything works as expected till this point beside saving settings (both global and individual cell module) doesn’t work for me, I receive 500 error.
btw. maybe it’s good to add more control app debug to serial output ?
sorry, it just started to save my calibration settings flawlessly.
I’m more than happy with my BMS, going to connect relay board now.
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If you want a glimpse of what’s to come, try the code out of this branch
https://github.com/stuartpittaway/diyBMSv4Code/tree/modulepwmchanges
You will have to reprogram the controller and all the modules!