HC05 standalone connected but won't send to terminal (Solved by changing OS) - Page 1
Forum section: electronics / general

author: maoterk
author_rank: Newbie
timestamp: February 21, 2019, 01:45:18 pm
content: I have successfully send data to a terminal using the HC05 board but i can't do the same with my circuit that uses the standalone board. The pc recognizes the standalone version i made but nothing turns up in the terminal although i tested with oscilloscope and the TX signal is ok. I have a com configured for the hc05.The microcontroller controlling it is an stm32 so VCC=3.3. I just realized i use s slightly different version of the board. Does it matter?Any ideas please?thanks

author: wrynczuk
author_rank: Newbie
timestamp: February 21, 2019, 08:00:34 pm
content: Have you verified the UART baud rate at which your HC05 is operating? You might have done it for your original setup days ago and got used to the new speed.Orginally HC05 operates at 9600 bps. When switched to the AT command mode it works at 38400 bps. Then using AT commands it can be reconfigured to required speed.

author: maoterk
author_rank: Newbie
timestamp: February 22, 2019, 10:50:17 am
content: It works now, but is taking a lot more time to establish connection compared to the first board i was using. There must be differences in the firmware that is creating these difficulties. I have to delete the hc05 from the pc every time to establish correct connection. That wasn't the case with the first board.thanks for the help though and beware of these cheap boards that have many different connections from board to board.

author: iMo
author_rank: Super Contributor
timestamp: February 22, 2019, 01:50:53 pm
content: The HC-05 goes into a "sleep" after 5 seconds of idle ("idle" means you do not send any data out of your MCU or you do not receive any data from air). That lowers the HC-05 current consumption from around 20mA to 2mA.In order to wake the HC-05 up you have to send a char into the HC-05 via air (from your PC for example).When in sleep the data from the MCU do not propagate out and the data are lost (you do not see incoming data in your terminal).Thus to keep the HC-05 always alive you have either send the data out of you MCU within 5secs period, or, send a char out of your PC within 5secs period.

author: jackthomson41
author_rank: Regular Contributor
timestamp: February 22, 2019, 02:21:59 pm
content: CheckHC-05 pinout, I think there's something wrong with the settings coz it's response time is excellent.If your microcontroller is on 5V then it's better to use a buffer for TX, RX pins i.e. CD4050.Try using capacitor between Vcc & GND, may be the slow response is because of power.

author: colorado.rob
author_rank: Frequent Contributor
timestamp: February 22, 2019, 07:46:27 pm
content: What operating system are you using on the PC? Microsoft recently broke Bluetooth SPP in Windows 10. It now only supports SPP 1.2, and the HC-05 is an SPP 1.1 device.

author: maoterk
author_rank: Newbie
timestamp: February 22, 2019, 08:18:52 pm
content: Yes, i have windows 10. The first board i was using had no issues so there must be a firmware issue.

author: maoterk
author_rank: Newbie
timestamp: February 22, 2019, 11:31:03 pm
content: I still face many connection issues. What could i do to fix this?Would a bluetooth dongle make any difference?

author: colorado.rob
author_rank: Frequent Contributor
timestamp: February 23, 2019, 08:48:28 pm
content: Try another OS. Does it work with Linux? Or Android?

author: iMo
author_rank: Super Contributor
timestamp: February 24, 2019, 10:06:10 am
content: Is that picture above your "standalone board"? Is that schematics the one for your module?Your 100pF cap there is a joke, it has to be at least 10uF tantalum or multilayer ceramic. I've been using 10uF/6V (or 10V) 0805 smd on my breakboards.Also there is a pin on the HC-05 (pin 34 ??) which needs to be pulled to "low" (GND) via a resistor (ie. 1k) AFAIK, the "high" (3.3V) on it initiates the "AT mode", it could be it is floating on your board and creates the mess. Doublecheck.Mind you need at least 3cm (1/4 wavelength) conductor/metal free space around the antenna for optimal antenna operation.I got several HC-05 mounted on my breakboards with below wiring and they all work fine (different baud settings 115k2..1M34, diff access passwords), multiple modules connected to a single PC in parallel operation, under win7 (2 diff PCs).

author: maoterk
author_rank: Newbie
timestamp: February 24, 2019, 11:18:00 am
content: The cap is 100pF for altium. (should stop being lazy)It works perfectly now, i just changed computers (windows 7 from windows 10).As colorado.rob said, there is an issue with window 10 and this particular device.

author: Buriedcode
author_rank: Super Contributor
timestamp: February 24, 2019, 11:45:07 am
content: Quote from: maoterk on February 24, 2019, 11:18:00 amIf you can pair it with your PC but can't get the comm port to open (and therefore, connect to) the bluetooth module:https://www.eevblog.com/forum/projects/bluetooth-hc-05-csr-4-0-windows-10-no-dice/It's a bug in windows 10 that can cause problems when trying to open virtual comm ports from bluetooth modules.edit: just noticed your reply in that thread! sorry, didn't check before I posted :/