# HC-05 without software serial? \ **URL:** \ **Category:** Networking, Protocols, and Devices\ **Created:** [March 16, 2018, 11:18pm UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635 "2018-03-16T23:18:48Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![navidivan](https://avatars.discourse-cdn.com/v4/letter/n/ecccb3/32.png) [@navidivan](https://forum.arduino.cc/u/navidivan)\ **Post date:** [March 16, 2018, 11:18pm UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/1 "2018-03-16T23:18:48Z")
Can I get this code transmiting the seconds to a bluetooth terminal? ---
**Author:** ![navidivan](https://avatars.discourse-cdn.com/v4/letter/n/ecccb3/32.png) [@navidivan](https://forum.arduino.cc/u/navidivan)\ **Post date:** [March 16, 2018, 11:24pm UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/2 "2018-03-16T23:24:44Z")
Is it possible to connect a bluetooth module (HC-05) to hardware serial pins (RX TX) of a 3.3 V arduino board? I really want to avoid using SoftwareSerial library, etc. ---
**Author:** ![ieee488](https://avatars.discourse-cdn.com/v4/letter/i/d2c977/32.png) [@ieee488](https://forum.arduino.cc/u/ieee488)\ **Post date:** [March 16, 2018, 11:55pm UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/3 "2018-03-16T23:55:44Z")
If you don't want to use software serial, you need to buy the Mega which has 3 hardware serial. ---
**Author:** ![Coding\_Badly](https://avatars.discourse-cdn.com/v4/letter/c/f14d63/32.png) [@Coding\_Badly](https://forum.arduino.cc/u/Coding_Badly)\ **Post date:** [March 17, 2018, 12:34am UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/4 "2018-03-17T00:34:13Z")
Threads merged. ---
**Author:** ![ieee488](https://avatars.discourse-cdn.com/v4/letter/i/d2c977/32.png) [@ieee488](https://forum.arduino.cc/u/ieee488)\ **Post date:** [March 17, 2018, 1:18am UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/5 "2018-03-17T01:18:13Z")
> navidivan: > Is it possible to connect a bluetooth module (HC-05) to hardware serial pins (RX TX) of a 3.3 V arduino board? I really want to avoid using SoftwareSerial library, etc. the HC-05 is 3.3V. ---
**Author:** ![CrossRoads](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/crossroads/32/214033_2.png) [@CrossRoads](https://forum.arduino.cc/u/CrossRoads)\ **Post date:** [March 17, 2018, 3:19am UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/6 "2018-03-17T03:19:56Z")
"the Mega which has 3 hardware serial." Serial1, Serial2, Serial3, in addition to Serial which is connected to the PC for programming, and is available as a 4th hardware serial otherwise. ---
**Author:** ![Nick\_Pyner](https://avatars.discourse-cdn.com/v4/letter/n/e8c25b/32.png) [@Nick\_Pyner](https://forum.arduino.cc/u/Nick_Pyner)\ **Post date:** [March 17, 2018, 5:33am UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/7 "2018-03-17T05:33:57Z")
> navidivan: > Is it possible to connect a bluetooth module (HC-05) to hardware serial pins (RX TX) of a 3.3 V arduino board? The answer to this question is yes. HC-05 is 3.3v. All Arduinos are OK with 3.3v from HC-05. With a 3.3v Arduino, HC-05 gets 3.3v from Arduino Tx, i.e. what it needs. For the wiring, this simply means that you omit the 1k/2k divider that is good practice to use on a 5v Arduino Tx. I don't know why you are asking about software serial, it would do nothing to solve a problem that you don't have. The question you are not asking, but may be irrelevant anyway, is powering the HC-05 module. You aren't saying what 3.3v Arduino you intend to use, but I understand most have a 5v pin for peripherals as well. I have seen a 3.3v Bluetooth but I believe it was an HC-06. If you don't have any 5v supply, this may suffice. Another choice is to use a bare HC-05 module on 3.3v. Only four pads need be connected, so the soldering job may not be as terrifying as it first appears. ---
**Author:** ![navidivan](https://avatars.discourse-cdn.com/v4/letter/n/ecccb3/32.png) [@navidivan](https://forum.arduino.cc/u/navidivan)\ **Post date:** [March 17, 2018, 5:57pm UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/8 "2018-03-17T17:57:49Z")
> CrossRoads: > "the Mega which has 3 hardware serial." Serial1, Serial2, Serial3, in addition to Serial which is connected to the PC for programming, and is available as a 4th hardware serial otherwise. I am not using a Mega. I am using a TinyTile which uses an intel Currie. The thing is, I don't need to stay connected to the PC. I am running the whole system on batteries. I upload the code, using the usb port, then use the native RX TX pins, which all of the arduino boards have at least one, to connect to HC-05. I should be able to communicate with "Serial", right? Does that seem right? I can not get it to work anyway. What might be the problem with this approach? ---
**Author:** ![navidivan](https://avatars.discourse-cdn.com/v4/letter/n/ecccb3/32.png) [@navidivan](https://forum.arduino.cc/u/navidivan)\ **Post date:** [March 17, 2018, 6:04pm UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/9 "2018-03-17T18:04:27Z")
> Nick\_Pyner: > The answer to this question is yes. > > HC-05 is 3.3v. All Arduinos are OK with 3.3v from HC-05. With a 3.3v Arduino, HC-05 gets 3.3v from Arduino Tx, i.e. what it needs. For the wiring, this simply means that you omit the 1k/2k divider that is good practice to use on a 5v Arduino Tx. > > I don't know why you are asking about software serial, it would do nothing to solve a problem that you don't have. > > The question you are not asking, but may be irrelevant anyway, is powering the HC-05 module. You aren't saying what 3.3v Arduino you intend to use, but I understand most have a 5v pin for peripherals as well. I have seen a 3.3v Bluetooth but I believe it was an HC-06. If you don't have any 5v supply, this may suffice. Another choice is to use a bare HC-05 module on 3.3v. Only four pads need be connected, so the soldering job may not be as terrifying as it first appears. the HC-05 asks for 5V Vin, but the RX-TX works on 3.3 V. I don't think I have a power problem. The HC-05 works fine with my current wiring if I use SoftwareSerial. Now my question is, since I don't need to stay connected to the PC anymore, I was wondering if I can use the hardware RX-TX pins to communicate with HC-05. So I want to upload the code using usb port, detach it, connect HC-05 to RX-TX hardware pins, and use Serial to send recieve data. Does that make sense? It does not work for me. ---
**Author:** ![GolamMostafa](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/golammostafa/32/239011_2.png) [@GolamMostafa](https://forum.arduino.cc/u/GolamMostafa)\ **Post date:** [March 17, 2018, 6:25pm UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/10 "2018-03-17T18:25:41Z")
> the HC-05 is 3.3V. The above circuit is tested for Vcc = 5V. The HC-05 is a 5V Module except that the RX-section of its UART port is not 5V tolerant. A voltage divider circuit brings down the 5V logic of the source Rx-signal down to 3.3V logic. Is it safe to operate HC-05 with Vcc = 3.3V? ---
**Author:** ![navidivan](https://avatars.discourse-cdn.com/v4/letter/n/ecccb3/32.png) [@navidivan](https://forum.arduino.cc/u/navidivan)\ **Post date:** [March 17, 2018, 7:20pm UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/11 "2018-03-17T19:20:24Z")
Hi all This must have been obvious to all of you pros. But I am newbie and it took me a while to figure this out lol. I feel so Stupid and Genius at the same time. The RX TX on the arduino boards should be called via Serial1. Serial is reserved for the usb port. So there is no need to use SoftwareSerial after all. all one needs to do is get RX to TX of Bluetooth (HC-05) and viceversa. Then the code should be: Serial1.begin(9600); Serial1.print("blah blah blah"); etc. ---
**Author:** ![navidivan](https://avatars.discourse-cdn.com/v4/letter/n/ecccb3/32.png) [@navidivan](https://forum.arduino.cc/u/navidivan)\ **Post date:** [March 17, 2018, 7:46pm UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/12 "2018-03-17T19:46:44Z")
How Can I change the Subject line of the thread and add "Solved" to it? ---
**Author:** ![anon94801460](https://avatars.discourse-cdn.com/v4/letter/a/278dde/32.png) [@anon94801460](https://forum.arduino.cc/u/anon94801460)\ **Post date:** [March 17, 2018, 8:06pm UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/13 "2018-03-17T20:06:58Z")
> navidivan: > How Can I change the Subject line of the thread and add "Solved" to it? Use the "modify" option to edit your post (More, lower right) and change the Subject line. ---
**Author:** ![ieee488](https://avatars.discourse-cdn.com/v4/letter/i/d2c977/32.png) [@ieee488](https://forum.arduino.cc/u/ieee488)\ **Post date:** [March 17, 2018, 9:58pm UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/14 "2018-03-17T21:58:24Z")
> navidivan: > Hi all > This must have been obvious to all of you pros. But I am newbie and it took me a while to figure this out lol. I feel so Stupid and Genius at the same time. > > The RX TX on the arduino boards should be called via Serial1. Serial is reserved for the usb port. So there is no need to use SoftwareSerial after all. all one needs to do is get RX to TX of Bluetooth (HC-05) and viceversa. Then the code should be: > > Serial1.begin(9600); > > Serial1.print("blah blah blah"); etc. The one and only hardware serial on the Arduino Uno is **Serial** not **Serial1**. ---
**Author:** ![Nick\_Pyner](https://avatars.discourse-cdn.com/v4/letter/n/e8c25b/32.png) [@Nick\_Pyner](https://forum.arduino.cc/u/Nick_Pyner)\ **Post date:** [March 18, 2018, 12:33am UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/15 "2018-03-18T00:33:48Z")
> GolamMostafa: > The above circuit is tested for Vcc = 5V. > Is it safe to operate HC-05 with Vcc = 3.3V? "Safe" is a relative term, but it can't be a good idea. People have done it, but you have 5v available and the label clearly says 3.6 - 6v, so why would you? Further, you have 50mA available on the 3.3v pin, and I understand that, during pairing at least, bluetooth gets close to demanding that, so why stretch the friendship? HC-0x are not famous for frugality in the power department, but that also be relative. Further information is available in the manuals, but I recall the word around here is that it is optimistic, and only applies to the bare module anyway. ---
**Author:** ![GolamMostafa](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/golammostafa/32/239011_2.png) [@GolamMostafa](https://forum.arduino.cc/u/GolamMostafa)\ **Post date:** [March 18, 2018, 6:54am UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/16 "2018-03-18T06:54:33Z")
> "Safe" is a relative term, but it can't be a good idea. People have done it, but you have 5v available and the label clearly says 3.6 - 6v, so why would you? > These small ( 3 cm long) modules run on 3.3V power with 3.3V signal levels, [(found here)](https://arduino-info.wikispaces.com/BlueTooth-HC05-HC06-Modules-How-To) ---
**Author:** ![Nick\_Pyner](https://avatars.discourse-cdn.com/v4/letter/n/e8c25b/32.png) [@Nick\_Pyner](https://forum.arduino.cc/u/Nick_Pyner)\ **Post date:** [March 18, 2018, 7:49am UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/17 "2018-03-18T07:49:21Z")
That is the bare module alluded to in reply #6. It is usually used on a breakout board. ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [May 6, 2021, 11:09am UTC](https://forum.arduino.cc/t/hc-05-without-software-serial-solved/514635/18 "2021-05-06T11:09:59Z")