Bluetooth options

You're probably right. I did find this page, which made me a little concerned, but he did say that relatively low resistor values gave a decent square wave.

Very interesting, but I think you are just being blinded by science. I’m sure nobody uses anything but simple resistors, and I don’t use anything at all.

I use logic chips anytime high speed signals are involved. Such as 74HC4050 for 5V to 3.3V. 74HC125 for 3.3V back to 5V, mainly on MISO signal, so the 3.3V device is not exposed to 5V from other devices, and also so the 3.3V device is totally kicked off the SPI bus when it is not selected, and cannot drag the level down (with clamp diodes or something) for the 5V devices.

Nick_Pyner:
I’m sure everybody else uses 1k/2k resistors, so, no.

Ok, good point. And if the board is a 5v board, why convert anything to 3.3v. You did say it was a good idea. If it isn’t necessary, why do it at all? Have you ordered one of these Banggood boards? I’m still waiting on mine.

Hoping this thread is still about HC-0x.........

These are 3.3v devices.

They are typically mounted on a backboard called JY-MCU. This has become a generic term.

These backboards come with a level shifter for VCC and are clearly marked Power 3.6 - 6v, which implies that feeding them 3.3v is a mistake.

But they do not have on-board shifters for Tx,Rx and are marked on the back "Level 3.3v". This means that feeding the Rx from a 5v Arduino via a divider in the manner described is a good idea.

But the Tx from bluetooth is already 3.3v. A 5v Arduino is OK with that, no shifting required.

The reason why I haven't done it is because I didn't know about it. My stuff has been running for a couple of years and never had a problem, but I would not recommend it.

Aargh. The Banggood modules just arrived. Even though I ordered this, I got this. So I don't have the HM10 board. I'm not sure where to go from here. I could try to re-order the correct boards, but they would take almost another month from Hong Kong. Or could I just get JY-MCU modules and solder these thingies onto them? I got screwed by Banggood, although looking back at the confirmation email I got from them, they did say that they were sending me the wrong thing. For $15, it's not worth fighting about it, I just want to get this working and get on with my project.

Ah, even if just vicariously, this is getting interesting.....

I see that the two modules are different. The one on the board has 13 pads each side and the bare one eight. The bare module I have has 13 pads. I forgot to get the JY-MCU backboard, so I'm still waiting.

Banggood are likely to come good, particularly if they have already acknowledged that they stuffed up. They might even tell you to keep the first package..

Sheesh. You're right. I didn't even notice that. One is the TI CC2540, and the other is the CC2541. I don't know the difference, but presumably the JY-MCU takes the CC2541.

At this point, I can't even say for sure what I ordered. I know I intended to order the cc2541 module, and that's what I thought I ordered, but maybe I clicked on the wrong thing accidentally. Even if Banggood came through and sent me the correct one, I'm still going to have to wait almost a month to get it. They send these things via donkey, as you know.

I really can't afford to wait another month. If you know where I can quickly get a JY-MCU/CC2541 that I can use in my prototype, please let me know!

Never mind, I just noticed that Banggood offers 3-7 business day expedited shipping. I wish I'd noticed that in the first place. That seems like my best option. But if you know what the difference between the cc2540 and 2541, and/or what I can do with these 2540s I have, let me know!

I don't dare guess, I have never seen them before. The world of HM-10 is still rather murky. It is just possible that one is an HC-06 equivalent. Most of the pads on the HC-06 are redundant and maybe they want to rationalise.

I recall Banggood is in HongKong and their mail takes about ten days - slightly better than typical of China. If it takes much longer, it is your local service that is suss. Sometimes the Chinese amaze me and get stuff here in a week. I have wondered if they work in specially-built skyscrapers with a post office at ground level and they drop stuff down a communal chute.

EDIT Google cc2540 vs cc2541

I now understand the 2541 is a newer, even lower power successor to the 2540. It also has more facilities, like 12C. I'm not interested in that stuff, I just want an HC-05 equivalent, and it appears that it can do that.

Ok. But the JY-MCU can only take the cc2541, right? Anything like that that could take the cc2540?

dptdpt: Ok. But the JY-MCU can only take the cc2541, right?

I strongly suspect that is right. I have never seen it done, but there is a small race on to see who is first to do it.

Anything like that that could take the cc2540?

I don't think so. The 2540 is probably obsolete anyway, and not worth pursuing. I think Banggood should come good on their mistake.

Ok, I (finally) got my BLE modules from Banggood. I'm talking about these. And I now realize that they aren't actually HM10 modules (according to comments on Banggood's page). They are this. I had thought I was getting HM10 modules. Banggood actually now does offer HM10 modules, for about twice the price here.

Since this is my first BT project, I don't know whether I should care. What I need to be able to do is to:

  • Change the device name to one of my choosing
  • Pair with the device from both iPhone and Android
  • After pairing, have bidirectional communication between the smartphones and the device.

Any reason why this can't do any of that?

  • Dave

dptdpt: Since this is my first BT project, I don't know whether I should care. What I need to be able to do is to:

  • Change the device name to one of my choosing
  • Pair with the device from both iPhone and Android
  • After pairing, have bidirectional communication between the smartphones and the device.

Any reason why this can't do any of that?

I think you shouldn't care, and there aren't any reasons why you can't. Your only problem might be with the Iphone, which could be a dog chasing car situation, but even that could change.

I have my cc25s41 and JY-MCU board now, but I'm afraid I have not had time to get it together.

Dog chasing car situation? I don't know that one... Iphone is actually what I need to get working first. If you know of any documentation I can refer to I'd appreciate it. These Banggood modules came with none.

Ok, I've gotten so far as being able to send the device AT commands from RealTerm. The AT command documentation they have for this guy is here. It's pretty limited. I haven't verified if it actually supports more than this.

But - bad news, for me at least. I have a BLE USB dongle for my Windows PC, and from that, I am able to see the Banggood BLE module. When I go to Bluetooth Devices on my iPhone. I don't see it.

Any thoughts what might be going on?

Update. I have had some (sort-of) success. On the page I referenced earlier, the links to some sample iPhone code that he says will talk to the module. I was skeptical since I don't see the module under Bluetooth devices, but I loaded that code onto my phone and it did indeed see the module (!). So, clearly there is a lot going on here that I don't understand, but it does appear that you can talk to the Banggood module from an iPhone.

dptdpt: Dog chasing car situation? I don't know that one...

Just ask yourself what the dog is going to do when he catches it........ I guess what you are experiencing is the Apple bluetooth protocols. It sounds like progress, which is good.

(Such is life - on the cutting edge)

Update: I've got the Bangood module working with two way bluetooth communication to a Pro Mini from an iPhone. Now onto building a BT Atmega bootloader!