Flashing the HM-10 firmware on a JDY-08

In my previous post I looked into the JDY-08 trying to put it to some use. I actually got it working but the default firmware is very crippled and (for me most importantly) lacks any power saving features. I managed to write the official HM-10 firmware to it, although that's as far as I've come... The device didn't do much afterwards.

Warning: this will most likely brick your JDY-08. I'm documenting it here just in case someone comes along and manages to get it to work anyway.

Connecting

So here's the connection table. See my previous post for how to solder them. Also see the forum thread with much more detailed instructions.

Of course also connect VCC and GND and use a level shifter (the JDY-08 is not 5V tolerant).

Getting the tools ready

So the next step is getting the tools ready. Upload the Arduino sketch to your Arduino (I've used an UNO) and download the CCLoader software for your OS. I've used Linux for which I compiled it manually, as there was no Linux binary provided and I would rather check and compile the source code myself instead of downloading and running a binary blob from the internet.

The command accepts 3 arguments, with device code being 0 for the Uno (ATmega328) and 1 for the Leonardo (ATmega32u4):

$ ./ccloader <serial port> <firmware.bin> <device code>

This is the first output I got:

$ ./ccloader /dev/ttyACM0 HMSoft.bin 0
Comport open:
Device  : Default (e.g. UNO)

Baud:115200 data:8 parity:none stopbit:1 DTR:off RTS:off
File open success!
Block total: 496
Enable transmission...
Request sent already! Waiting for respond...

It turns out it is necessary to connect a 10µF capacitor between the GND and reset pins. This took me a while to figure out. CCLoader opens a new serial connection which causes the UNO to restart, probably missing the first few bytes it sends.

So, my next try:

$ ./ccloader /dev/ttyACM0 HMSoft.bin 0
Comport open:
Device  : Default (e.g. UNO)

Baud:115200 data:8 parity:none stopbit:1 DTR:off RTS:off
File open success!
Block total: 496
Enable transmission...
Request sent already! Waiting for respond...
No chip detected!
Program successfully!
File closed!
Comport closed!

If you have read my previous post, you may know the P22 pin was broken. Well, I scratched open some of the blue surface to get to the trace leading away from it. Now I knew the Arduino was actually working as a CCLoader device, I actually tried holding a jumper wire on it... this required a pretty steady hand.

$ ./ccloader /dev/ttyACM0 HMSoft.bin 0
Comport open:
Device  : Default (e.g. UNO)

Baud:115200 data:8 parity:none stopbit:1 DTR:off RTS:off
File open success!
Block total: 496
Enable transmission...
Request sent already! Waiting for respond...
Begin programming...
1  2  3  4  5  6  7  8  9  10  11  [...snip...]  494  495  496  Program successfully!
File closed!
Comport closed!

Finally, a successful upload! This whole process took 1½ minute, uploading all the blocks. Due to a bug in ccloader there was not much output during the upload (it wouldn't flush stdout). But it looks like it did the job.

Unfortunately, I can't get it to work. The device doesn't show up in the nRF Toolbox and I can't get serial to work. I tried basically every baud rate on both pins P02/P03 and P16/P17 (the latter ones being the UART pins according to the HM-10 datasheet.

Maybe someone else gets a bit closer? For now, I've given up on the device. It's practically bricked and while it's cheap, it costs me too much effort to get it to work.