Programming through HC-05 bluetooth

Wireless & IoT
1

Hi, Everyone!

I’m having trouble sending sketches through HC-05 bluetooth adapters. One of them is connected to a Sparkfun Thing Dev ESP8266 Wifi board, and the other is connected to an Arduino Pro Mini. I could really use some help determining what’s wrong with my setup or if I have defective adapters.

First off, both the Pro Mini and Thing Dev take sketches just fine over a USB to Serial FTDI adapter. It’s only when I try to go wireless that I have trouble.

Starting with the Pro Mini connection, I’ve narrowed the problem on this one to a STATE/RST/GRN pin issue. I can get the sketch to load if I manually press the reset button on the Pro Mini as soon as the sketch starts to upload over bluetooth, so I know the TX and RX are working. But the HC-05 doesn’t seem to pulse anything to trigger the reset automatically. It’s set for AT+Polar=1,0. Changing that to =1,1 doesn’t make a difference. I tried a 10uF capacitor wired in series between STATE and RST/GRN, but that also changed nothing. Any other ideas?

Connections are:

TX to RX

Rx to TX

STATE to GRN

VCC to 5+ from power supply

GND to GND

I doubt this helps, but the vague error I get is:

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x00

Now, the Sparkfun Thing Dev (ESP 8266 Wifi board) connected to another HC-05 returns a different error:

esptool v0.4.9 - (c) 2014 Ch. Klippel <ck@atelier-klippel.de>

  • setting board to nodemcu*
  • setting baudrate from 115200 to 115200*
  • setting port from /dev/tty.usbserial to /dev/cu.TCloudThing-DevB*
  • setting address from 0x00000000 to 0x00000000*
  • espcomm_upload_file*
  • espcomm_upload_mem*
    opening port /dev/cu.TCloudThing-DevB at 115200
  • tcgetattr*
  • tcsetattr*
  • serial open*
    opening bootloader
    resetting board
    trying to connect
  • espcomm_send_command: sending command header*
  • espcomm_send_command: sending command payload*
    warning: espcomm_sync failed
    error: espcomm_open failed
    error: espcomm_upload_mem failed
    error: espcomm_upload_mem failed

And as soon as the upload fails, the HC-05 resets the Thing Dev. I’m not sure if it’s supposed to reset at that point or earlier? I found that it doesn’t reset at all if I disconnect the STATE pin, so at least I know it’s doing something here. Also, manually pushing a reset button doesn’t allow the signal to go through like it does with the Pro Mni above. This leads me to believe that the problem lies with the comm lines RX and TX between the Thing Dev and the HC-05. I have this HC-05 set to at+uart=115200,0,0. 115200, I believe is the standard baud rate for the Thing Dev. And at+polar=1,0

Connections are:

RX to TX

TX to RX

STATE to RST

GND to GND

VCC to VIN

Any ideas on what to try next would be much appreciated.

2

Well, after far too many hours of struggle, I figured out what was wrong with the Pro Mini connection. It was actually due to two issues.

  1. The HC-05 adapter I was using with the Arduino had a defective STATE pin.

  2. I skipped the GRN pin on the end of the Pro Mini, and instead connected the STATE pin of a working HC-05 to the RST pin with a capacitor. The capacitor is definitely necessary, though I’m not sure if the 10uF capacity is significant. That’s just the size I had sitting around. The GRN pin would only reset if I manually pulled it high and then low in alternating fashion–very strange. Perhaps that’s due to some kind of auto-reset circuit.

Anyway, now I can reliably upload sketches over bluetooth to my Pro Mini. Yay.

I gave up on adding a bluetooth serial connection to the Sparkfun Thing Dev. Further reading led me to conclude that the reset function on that board works differently than the Pro Mini?..possibly requiring some connection to PIO0, but Sparkfun has no helpful documentation on it. I’ll table it until somebody here with more experience chimes in.