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1  Using Arduino / General Electronics / JY-MCU bluetooth module V4.0 alternative on: April 25, 2014, 07:41:55 am
Hello,

i was working with JY-MCU quite a lot. It's cheap enough and since i am usually working only with slave devices, it's a good choice (IMHO).

I am looking for cheap alternative, which would support bluetooth V4.0, but they are a lot more expensive. I found two modules but both without socket and power regulator (interface board).

http://www.ebay.com/itm/HM-10-CC2540-4-0-BLE-Bluetooth-to-UART-Transceiver-Module-Central-Peripheral-/231212878227?pt=LH_DefaultDomain_0&hash=item35d55c8993
or
http://www.fasttech.com/products/0/10004051/1292002-ti-cc2540-bluetooth-40-ble-2540-transparent-serial

Does anybody know for V4.0 module with interface board in (approximately) price range of JY-MCU?
2  Using Arduino / General Electronics / Re: PT1000 and Callendar-Van Dusen Equation question on: April 22, 2014, 05:54:16 am
I used the equation in a spread sheet and it works fine.

You're right, it works. I made mistake while inserting A and B coefficients smiley
3  Using Arduino / General Electronics / [SOLVED] PT1000 and Callendar-Van Dusen Equation question on: April 22, 2014, 04:04:09 am
Hello,

i want to calculate temperature from resistance of PT1000 with Callendar-Van Dusen equation. I am using equation for temperature which i found here -> http://www.code10.info/index.php?option=com_content&view=article&id=82:measuring-temperature-platinum-resistance-thermometers&catid=60:temperature&Itemid=83

I tried to calculate temperature from it. I took R=1093,5 ohms because from PT1000 table it fits to 24 °C. I calculated it three times but i always get 2,393247. If i multiply this with 10 it's about 24, what would be correct but that's not what equation says.

I am wondering what i am doing wrong.. Did i miss any part of equation or?
4  Using Arduino / General Electronics / Re: [SOLVED] Bluetooth module serial communication problem on: April 13, 2014, 02:50:42 pm
Yes it would be a good idea.

Ok, i will include jumper on that line on PCB. All other lines of BT module (VCC, GND, RX) can be connected during uploading new sketches.

Thank you for all advices! smiley
5  Using Arduino / General Electronics / Re: [SOLVED] Bluetooth module serial communication problem on: April 13, 2014, 12:44:17 pm
One more question..

Should i disconnect the line from arduino RX to bluetooth TX while uploading new sketches in that case?
6  Using Arduino / General Electronics / Re: [SOLVED] Bluetooth module serial communication problem on: April 13, 2014, 03:27:51 am
But you have 6 components using that chip!

You're right, i was a little bit to fast.. Looking datasheets late in night is not good idea smiley-grin

I tried this. Voltage divider for TX-RX and to get 3.3V reference voltage and part with transistor for RX-TX (Arduino-BT).

It works.
7  Using Arduino / General Electronics / Re: [SOLVED] Bluetooth module serial communication problem on: April 12, 2014, 05:26:39 pm
No it is not, you do not need anything bidirectional and you do not need an I2C bus level translator.

I am planning to use it for both sides (also from Arduino TX to bluetooth RX), to avoid voltage divider. I know i don't have I2C but it will work anyway, right? I would like to use this because is small and cheap enough. With this device i don't need 6 (or more) different components on the PCB.

Btw, do you know what would be BSS138 alternative in THT?
8  Using Arduino / General Electronics / Re: [SOLVED] Bluetooth module serial communication problem on: April 12, 2014, 10:59:19 am
I found PCA9306. Dual bidirectional LLC which is cheap and big enough for easy soldering. That's exactly what i need smiley

http://www.ti.com.cn/general/cn/docs/lit/getliterature.tsp?genericPartNumber=pca9306&fileType=pdf
9  Using Arduino / General Electronics / Re: [SOLVED] Bluetooth module serial communication problem on: April 12, 2014, 09:13:07 am
I will try with 2n3904..

Btw, this thing is not bidirectional, right? If i would like to do bidirectional version i would need to use FET (something like BSS138 just in TO-92 housing, for easier handling).
10  Using Arduino / General Electronics / Re: [SOLVED] Bluetooth module serial communication problem on: April 12, 2014, 08:50:47 am
Why a couple? You only need one:-

I created my own 2 channel LLC, based on sparkfun LLC -> https://www.sparkfun.com/products/12009

Now it works, without pull-up.

Grumpy_Mike, which type of transistor would fit in this scheme? I used BSS138 but it take me A LOT of time to solder them (they are sooo small). Can you recommend some kind of replacement in TO-92 housing or a little bigger SMD version?
11  Using Arduino / General Electronics / Re: [SOLVED] Bluetooth module serial communication problem on: April 11, 2014, 04:36:48 am
It might do for now but by pulling up that line you are in effect putting 5V on the BT module's output. As this is a 3v3 device this could damage it. Some devices are tollerent to this sort of thing but many are not.

I don't know why you would need to do this. It doesn't sound like a great idea, and it might be better to find out what the real problem is.

I tried direct connection to RX line of Arduino but it didn't work. I tried with two different bluetooth modules and with 3 different boards (Uno, Nano and stand-alone Arduino) but result was the same. The only way i could make it work was to add pull-up on that line. In other way (Arduino TX to bluetooth RX) with voltage divider it works like it should.

I think the problem is that signal for logical "1" from 3,3V BT module is too low for Arduino to understand it but i don't know why or how to fix it. Btw, lines are just a few cm long, i tried on breadboard and PCB -> No luck.
12  Using Arduino / General Electronics / Re: [SOLVED] Bluetooth module serial communication problem on: April 10, 2014, 03:02:00 am
JY-MCU transmits with 3.3v. Assuming your Arduino is 5v, it doesn't normally care about receiving a 3.3v signal but, if the wire is very long and there are some losses, maybe it isn't enough.  Normally, the concern is the other way, with Arduino sending a 5v signal to the JY-MCU's 3.3v Rx.

I putted voltage divider on other side (TX to BT RX) so that's not a problem. With 10k pull-up resistor on line from BT TX to Arduino RX, it works ok, without errors.
13  Using Arduino / General Electronics / [SOLVED] Bluetooth module serial communication problem on: April 06, 2014, 10:28:09 am
I found solution for this problem, in case that anyone will have the same problems.

I add 10k pull-up resistor on line, which goes from arduino's RX to TX of bluetooth module. Now it works like it should. I still don't know what's the problem but i think that signal for logical "1" from BT module is too low for arduino.
14  Using Arduino / General Electronics / Re: Bluetooth module serial communication problem on: April 01, 2014, 04:49:05 am
The only change you make is disconnecting the FTDI's TX and RX?

Yes, exactly.

It can hardly be the code and the wiring looks kosher, so it sounds like inadequate power.

I tried also with LM7805 and external adapter so i don't believe the problem is in power.

What's the normal state of TX, RX and RESET pins of FTDI cable, when not programming? Is possible that lines are too long?


15  Using Arduino / General Electronics / Re: Bluetooth module serial communication problem on: March 31, 2014, 05:23:29 pm
Source is the same because i am powering from the same FTDI cable (pluged into computer over USB), just that i connect only +5V and GND from FTDI cable (with 2 connection wires).
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