Looking for suggestions: Wireless serial UART

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#1
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Hi all,

 

Simple enough (I think).....

 

What I am looking for is a small, simple module that would run at probably 915 MHz. or 2.4 GHz. and simply have  VCC and GND pins, Serial RX and TX pins and maybe a few for module setup/config.

 

I've been looking at a bunch of different kinds and I can't seem to figure out which one offers what.

 

For example, I found one that accepts "serial AT commands" which at first I thought it's what I wanted, but looking further I see it's only for control, not data transmission.

 

Sort of like the sketch below.

 

radio.jpg

 

Thanks.

Gentlemen may prefer Blondes, but Real Men prefer Redheads!

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I've has some good luck with these....however, they aren't fast, if you are looking to shove a lot of data, or you need very low response latency. 

 

http://www.rfdigital.com/product/rfd21733-rfdp8-rf-module-4/index.html

 

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Sun. Nov 18, 2018 - 05:16 AM
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EOL

https://www.mouser.com/ProductDetail/RF-Digital-Wireless/RFD21733?qs=%2fha2pyFaduh2vXRhnAgjxY30Nhn8WJhfJZnpmOrzy4E%3d

Simblee might be considered as the follow-on to RFDP8; scratch, Simblee is EOL : https://www.arrow.com/en/products/rfd77101/rf-digital-corporation

RFDP8 and Simblee are coin cell friendly.

 

RFDP8 couldn't withstand Bluetooth 5 with its range enhancements and mesh network.

Seems each Bluetooth 5 manufacturer has SPP over Bluetooth Low Energy; most have an SDK so can port the application into their Bluetooth 5 SoC.

 

Edit: scratch

 

"Dare to be naïve." - Buckminster Fuller

Last Edited: Sun. Nov 18, 2018 - 06:08 AM
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What data rates are you looking for?
Does it need to be license exempt?

#1 This forum helps those that help themselves

#2 All grounds are not created equal

#3 How have you proved that your chip is running at xxMHz?

#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Krupski wrote:
... Serial RX and TX pins and maybe a few for module setup/config.
9600bps to 115200bps UART plus one signal for command mode for 1.6km LoS :

Linx Technologies - Basic Configurations for Sending Data with the HumPROTM Series RF Transceivers

via HumPRO™ Series RF Transceiver Module - Linx Technologies

UART plus more discretes : 

Transparent RF Modules Archives - Linx Technologies

 

"Dare to be naïve." - Buckminster Fuller

Last Edited: Sun. Nov 18, 2018 - 01:52 PM
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gchapman wrote:

Krupski wrote:

... Serial RX and TX pins and maybe a few for module setup/config.

 

9600bps to 115200bps UART plus one signal for command mode for 1.6km LoS :

Linx Technologies - Basic Configurations for Sending Data with the HumPROTM Series RF Transceivers

via HumPRO™ Series RF Transceiver Module - Linx Technologies

UART plus more discretes : 

Transparent RF Modules Archives - Linx Technologies

 

 

Now THAT'S what I'm looking for!

 

BTW, what I plan to use it for is remote data acquisition in a University lab where the experiment cannot have anyone near it (x-ray hazard).

 

The data rate will be low... probably no more than a few 1000 bytes per second.

 

Thanks for the info!

 

Gentlemen may prefer Blondes, but Real Men prefer Redheads!

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avrcandies wrote:

I've has some good luck with these....however, they aren't fast, if you are looking to shove a lot of data, or you need very low response latency. 

 

http://www.rfdigital.com/product/rfd21733-rfdp8-rf-module-4/index.html

I have used these transceivers with good luck for a bunch of years, however they are no longer available.  Digi-Key shows them as obsolete, and other suppliers I used to use no longer have them.  I am also looking for a replacement.

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however they are no longer available

uh-oh...strange, the website (www.rfdigital.com) still shows them.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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avrcandies wrote:

however they are no longer available

uh-oh...strange, the website (www.rfdigital.com) still shows them.

 

Yes, but if you click on the Sales link you will find none of the distributors have any.  They have not been available for at least 6 months.  I wanted to stock up on them and couldn't find anyone that had any.

 

If you find someone that has some can you let me know.  I would like to have a few more as I have several projects that use them.

Last Edited: Sun. Nov 18, 2018 - 11:48 PM
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if you do a Google on RFDigital AMS you will find RFDigital was acquired by Heptagon in 2016, and then ams AG acquired them both, but I'm not sure when.  What is going to happen to the RFDigital line is unclear to me.  I like their little transducers.  Really easy to use, and with the built in antenna I could get line of sight ranges of 100m.  I still have a couple, but I wish I had a dozen more.  I need to find a new radio to replace them in my projects.  Maybe I will go Bluetooth.

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I've used these at 5 or 10 km through light bush and at 1 or 2 km through suburbia.

 

http://store.rfdesign.com.au/rfd...

 

They are made by a friend of a friend of mine.

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I found one that accepts "serial AT commands" which at first I thought it's what I wanted, but looking further I see it's only for control, not data transmission.

Are you sure?  Some devices accept AT commands for setup, and have an additional command for "enter transparent transmission mode" (just like the Hayes modems the command structure is copied from.)

 

For example, the ESP8266 devices (with their default "TCP module" firmware) seem to call this "unvarnished trasnsmission mode", and I'm pretty sure you could set up a pair of them to do behave the way you want.  There are a number of similar WiFi modules from the like of LantronixWiznet, and Digi

(I believe Digi in particular has (nearly) command-compatible modules with a bunch of different radios.)

 

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You're welcome.

Krupski wrote:
The data rate will be low... probably no more than a few 1000 bytes per second.
Approximately 1KB/s for Microchip Bluetooth Low Energy modules with transparent UART (SPP over Bluetooth Low Energy) [SPP over BLE]; greater speed by other manufacturers modules.

BLE advantage : operator's interface is a PC, tablet, or smart phone

BLE disadvantage : short range

Wi-Fi can have an extended range of 1km to 100km by antenna gain; likewise with Bluetooth.

A university may have spare 2.4GHz directional antennas; one can make an inexpensive 2.4GHz directional antenna.

Given system RF gain and range and heights and estimated loss (vegetation, walls, etc), BER or SNR can be computed by an RF link budget calculator (some are on public web servers)

Some Microchip BLE modules recently obtained a Bluetooth 5 certification (range increased, Wi-Fi interference decreased, enhanced mesh networking); looked at BM71 and BM78.

BM71 : transmitter power = 0dBm typ, receiver sensitivity = -90dBm typ, 3.0V typ, 10mA typ (coin cell)

BM78 : transmitter power = 0.5dBm typ, receiver sensitivity = -92dBm typ, Li-ion typ with 3.3V 50mA LDO for the external MCU

Cypress Semiconductor EZ-BTTM :

CYBT-353027-02 : transmitter power = 9dBm typ, receiver sensitivity = -96.5dBm typ, 2.3V .. 3.6V, up to 60mA typ

Might be able to reach the required range with some modules as-is; Microchip modules would have an external antenna with significant gain.

Mesh networks have range due to modules relaying packets; a mesh network has an IP capability by a gateway.

 


Cantenna - Wikipedia

How to build a tin can waveguide antenna

Bluetooth | Microchip Technology

BM71 - Bluetooth Module - Wireless

BM78 - Bluetooth Module - Wireless

BM70/71 Bluetooth Low Energy Module User's Guide

(page 16)

1.1.2 System Operation

The BM70/71 module has two main configuration options which affect the overall BLE and hardware behavior available to the host. The two configurations are:

• Auto Operation Configuration: Auto Operation restricts the available BLE operation by only allowing the BLE peripheral to act as a raw data pipe. This is compatible with hosts who only require the BM70/71 module to act as a virtual UART cable between the host and the remote peer device

• Manual Operation Configuration: Manual Operation provides the host the most functionality and control over the BM70/71 BLE protocol and operation. This configuration is used by a host to leverage the flexibility and feature set offered by both the BLE protocol and the BM70/71 module

BM7x are not extendable (added functionality) though are configurable (UART, discretes); Microchip has BLE SoC that are extendable via Atmel Studio 7.

CYBT-353027-02: EZ-BT™ WICED® MODULE

via

EZ-BLE and EZ-BT Bluetooth Modules

...

 

Additional Module Solutions Coming Soon

     

...

CYBT-483039-02:  Having range issues?  The CYBT-483039-02 module is certified up to +20 dBm output power and is targeted at a BLE connection range >1km.

...

 

EZ-BLE/EZ-BT Module Highlights

...

  • Long-range BLE options for up to 400 meters line-of-sight communication

...

... and EZ-Serial

...

  • Wide operating voltage (1.9 to 5.5 V)
  • Industrial (-40°C to +85°C) and Extended Industrial (-40°C to +105°C) temperature range options

 

"Dare to be naïve." - Buckminster Fuller

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Krupski wrote:

<...>

BTW, what I plan to use it for is remote data acquisition in a University lab where the experiment cannot have anyone near it (x-ray hazard).

<...>

 

 Which assumes that lab equipment and, most likely, the lab itself is shielded with sort of metal panels, right? Anyway, before chosing a transmitter by speed and range, I'd start with EMC, considering both RF transparency of the premises and chip resistance to X-ray.

 You won't believe it but once it took me two days to figure out that a GPS board fails all outdoors tests because its DC/DC converter could not work in direct sunlight. And that was just UV, not X-ray.


Qoitech AB, The Home of Otii Arc, an SMU for every developer

Check out Otii solution at www.qoitech.com

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MarkThomas wrote:
... and other suppliers I used to use no longer have them.
Not much RF Digital product at distributors.

Mouser has some stock of one RF Digital nRF24LE1 module but that's without RF Digital's RFDP8 firmware.

Is there a nRF24LE1 SDK?  Yes

Otherwise, an RF megaAVR and its mesh networking stack for range (or, gain by a power amplifier and/or antenna)

 


https://www.mouser.com/ProductDetail/RF-Digital-Wireless/RFD21734?qs=%2fha2pyFaduhYv4A8eWEj85m%2fAf%2fA0yI1h1dB%252blHyzvM%3d

nRFgo SDK / 2.4GHz RF / Products / Home - Ultra Low Power Wireless Solutions from NORDIC SEMICONDUCTOR

ATmega64RFR2 - Wireless Modules - Wireless (on-sale at Digi-Key)

https://www.microchip.com/mymicrochip/Reports.aspx?type=cpn&filter=atmega128rf

 

Edits: nRFgo, Digi-Key

 

"Dare to be naïve." - Buckminster Fuller

Last Edited: Mon. Nov 19, 2018 - 07:26 AM
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westfw wrote:

Are you sure?  Some devices accept AT commands for setup, and have an additional command for "enter transparent transmission mode" (just like the Hayes modems the command structure is copied from.)

 

What does AT mean?

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I believe it's short for ""Attention". That is "Oi modem, I'm about to ask you to do something"

 

EDIT: yup, Wikipedia agrees: https://en.wikipedia.org/wiki/Ha...

 (also called the AT commands: "AT" meaning 'attention')

Last Edited: Mon. Nov 19, 2018 - 05:38 PM
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Re: Cantenna

2.4GHz Yagi in a Can

by 

...

To test my antennas I use a test router 40 meters away with the signal going through three brick walls.

 

Edit: by-line

 

"Dare to be naïve." - Buckminster Fuller

Last Edited: Mon. Nov 19, 2018 - 05:50 PM
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clawson wrote:

I believe it's short for ""Attention". That is "Oi modem, I'm about to ask you to do something"

 

EDIT: yup, Wikipedia agrees: https://en.wikipedia.org/wiki/Ha...

 (also called the AT commands: "AT" meaning 'attention')

 

Thanks Cliff.  Dont know how you found that.  For other devices, then, the AT commands are those used to set functional parameters within the device and not for data transfer back and forth.  Is that correct?

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Or can the AT command be a request for data, and then data follows?

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MarkThomas wrote:
Or can the AT command be a request for data, and then data follows?

AT commands are sent in command mode, ie. commands to the modem however if the ATO command is sent (Return to Online mode)

Then the data stream follows the command as that command string exits command mode.

 

Jim

 

Click Link: Get Free Stock: Retire early! PM for strategy

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I am using an AMS AS7262 six channel photo detector.  I can communicate with it using I2C or UART with AT commands.  There is a table of AT commands I can send to set gain and get data.  All the commands are prefixed with "AT".  I get it now.  I am having the usual trouble using Peter Fleury's I2C library and my ignorance, and may try using UART and AT commands.  Thanks all for the input.  It was very helpful.

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What does AT mean?

 https://en.wikipedia.org/wiki/Hayes_command_set

 

Hayes invented essentially the first "smart" modem, back when 300bps was common (1980.)  The "hayes command set" allowed you to set up various parameters and issue dial commands over the same serial port that would eventually be used for commuications; implemented a "command" mode and an "online" mode (and a clever way to shift between them, even when the dialup was active.)  You'd type commands like:
 

ATE1
ATM0
ATS13=65
ATDP5551212

(Turn on Echo, Turn off Speaker, set obscure setting#12 to 65, "dial pulse" the specified phone number.  Hopefully, it would shortly respond with "connect")

The "AT" leadin allowed autobaud amd rejection of most commands accidentally sent to the wrong mode.

 

This was widely copied, later standardized (V.250?), and people noticed that the syntax is easily extendable.  So SMS can be done to cell phones with a serial connection using AT comands, a cisco Terminal server can be configured to accept "ATDTmyhost.com", and many other wireless and wired comm modules use it as well...

 

https://en.wikipedia.org/wiki/Hayes_Microcomputer_Products

 

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Quote:
Microchip Bluetooth Low Energy modules with transparent UART (SPP over Bluetooth Low Energy) [SPP over BLE];

Did BLE finally get an SPP definition, or is this yet another semi-proprietary thing? Does it interoperate with any phone apps? I really want a BLE dongle that plugs into an rs232 port and harvests enough energy to use my phone as a “terminal”...

Last Edited: Tue. Nov 20, 2018 - 02:19 AM
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westfw wrote:
Did BLE finally get an SPP definition, or is this yet another semi-proprietary thing?
IIRC, there's no complete follow-on to SPP.

westfw wrote:
Does it interoperate with any phone apps?
Yes

Android, Google Play, Microchip Bluetooth Data :

...

 

Supports the following BLE profiles/services: ...

4. Custom Serial Chat (custom profile) 

...

 

...

 

3. BM70 /BM78 /BM64  :
Discover and connect LE device. Transfer text typed in the app to peripheral device. Transfer text file data, send and receive across the device and phone

 

...

similar for iOS

 

"Dare to be naïve." - Buckminster Fuller

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I realized an application 4 years ago, this application transmit and receives messages in the 800 Mhz band @ 2400 bauds. An application master TX/Rx , and peripherals Tx or Rx. The receiving modules and the transmitter are directly connected with the pin Tx / rx of an  ATmega 128 or  8515,  8535, ATTiny 168. The receiver is an AM8SF AUREL, and the transmitter a TX 8L25IA Aurel.

 

https://fr.rs-online.com/web/p/m...

https://fr.rs-online.com/web/p/m...

 

You have just to connect one Pin….

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Mark,

 

I would say you are clearly not old enough but I believe you are. You may remember back in the pre-internet days of "bulletin boards" when we connected up "acoustic couplers" to telephone handsets and we made connections at 300 baud, 1200 baud or the luxury of 2400 baud that the modems we used then generally all implemented the "Hayes command set". That is a method where the modem switched on in command mode. You "set it up" by sending it AT command likes ATE1 (switch command echo on), ATS0=1 (set number of rings before it "hooks" the line to 1) etc etc. At some stage you finally would ATD012345678 and it would dial that number. The modem at the other end would put out "calling tone" and the two modems would latch on to each other. The modem then switched to "data mode". So now you stopped sending "ATxx" command and you typed real things like "hello world" (or initially probably an ID and password) and that data streamed through to the other end. If you needed to get back into command mode you would type three +++ signs to tell the modem "stop sending everything I type to the other end but return to listening for AT sequences so I can tell you to do something". You might then type ATH0 which means "unhook the line" - that is "hang up". While the Hayes company failed to get a patent on their AT command set the one bit of this whole thing they did patent was the "+++" thing to get back from data mode to command mode. In fact, on the basis that you might be sending "+++++++..." to the other end for real they made it so it only switched with "+++"<1 second of no activity> and that's the bit they patented.

 

Now all the people who write bulletin board software and terminal software and so on at the time added "Hayes compatible" to their code by having it setup and then send the right sequences of ATxxx at the right moments. So other modem manufacturers said "we want to be compatible with bulletin board software XYZ or terminal program ABC" so rather than thinking up some other way to control their modem pretty much everyone copies what Hayes had done and so there were tons of Hayes compatible modems so "AT commands" became a bit of a "standard" but Hayes still owned the patent on the +++ then delay thing - not sure how many people they sued but most cloners got around it by not having the delay after the three +++.

 

AT was such a part of the whole communications scene in those days that it persists to this day. Many devices that want to setup a "data channel" in some way still use ATxx to get things setup though it has now involved adding a whole lot more commands than the 20 or so that the original Hayes modem had. When mobile phones started to offer data links (SMS and then GPRS and so on) they extended their command range so that you could now do things (conceptually) like ATSMS=07214387,"Hello folks" and it would send an SMS to that number of ATHTTP=www.avrfreaks.net (obviously not quite THAT simple) to make TCP/IP links over GPRS and so on.

 

Then when Bluetooth devices came along they also took on ATxx so to control a Bluetooth speaker (say) you might conceptually do something like ATVOL=11 to set the audio volume etc etc.

 

So from humble beginning Hayes and their AT commands are all pervasive to this day. 

 

I remember 30..40 years ago contemplating what "AT" might mean at the time - I think we all agreed it was "ATtention" as in "Attention, I'm about to ask you to do something". To find/verify that was simply a case of googling "AT command set wikipedia" to find the page I knew must exist.

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westfw wrote:
Quote:
Microchip Bluetooth Low Energy modules with transparent UART (SPP over Bluetooth Low Energy) [SPP over BLE];
Did BLE finally get an SPP definition, or is this yet another semi-proprietary thing? Does it interoperate with any phone apps? I really want a BLE dongle that plugs into an rs232 port and harvests enough energy to use my phone as a “terminal”...

 

"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"Wisdom is always wont to arrive late, and to be a little approximate on first possession."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

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westfw wrote:
Does it interoperate with any phone apps?
Yes

Arduino with RN4870/1 | Martyn Currey

...

(1/4 page)

Power the module, then use a BLE scanner app to find the beacon. Here I am using Android BLE Scanner by Bluepixel Technologies LLP but there are many similar apps.

...

 

Talking to the RN4870/1

[USB UART to RN4870]

...

“GNR” command
“GNR” gets the name of a connected device. Of course, for this to work the module has to be connected to something. With the serial monitor still open. Use the BLE scanner app to connect to the RN4870.

...

 

First Communications

...

Start the BLE Scanner app, if it does not automatically start scanning, hit the Scanner button at the bottom. You should see the RN4870 appear in the list.

Hit the CONNECT button, after the connection is made, select the Custom Ser[v]ice

...

We can now try sending data to the serial monitor.
["hello", "hello to you"]

...

 

Notify or Indicate?

...

 

Connecting Two RN4870 Modules Together

The RN4870s have a transparent UART layer built in. This means it is easy to get them connected and start sending data. This is very similar to how the HM-10s (and similar modules) work, and, if this is all you need you might as well go with HM-10s. They are cheaper and come on hobbyist friendly breakout boards.

...

 

Updating the Firmware

...

After updating, use a BLE scanner app to check the default services and characteristics.

 

...

 

[comments]

...

http://www.martyncurrey.com/arduino-with-rn48701/#comment-13786 by Martyn

The RN devices only support single connections. For a piconet you would need to use devices like the BTLC1000 and SAMB11. These support up to 8 simultaneous connections.

...

 

http://www.martyncurrey.com/arduino-with-rn48701/#comment-14150 by D

...

I’m considering using the RN4871 module as serial passthru device to transfer data from an old serial instrument (TX only, no flow control) to a tablet.

[Question]

[HM-10 and EMI]

[Martyn's reply]

[iOS is Bluetooth 4 and sub]

...

 

http://www.martyncurrey.com/arduino-with-rn48701/#comment-14309 by jack kemski

[RN4870 firmware 1.30 - spontaneous disconnects; work-around is to reboot]

...

My question is, for a serial UART application, only needing to transfer small amounts of serial data back, and forth, what modules would you recommend?

[Martyn's reply]

...

If power is a concern look at BLE modules sans breakout board. I’ve had good results using the HM-11. Good connections and fairly low power use. There are better options is power consumption is critical though.

 

...

via https://plus.google.com/u/0/106109247591403112418/posts/FsfJEkuVoV8

 

"Dare to be naïve." - Buckminster Fuller

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BM71 - Bluetooth Module - Wireless

BM78 - Bluetooth Module - Wireless

:

Arduino with RN4870/1 | Martyn Currey

 Ahh.  Apparently BM71/78 is the "microprocessor controlled" version, whereas RN4870/71 is the "Serial configurable modem-like device."  Same hardware, different firmware, according to some conversations on the Microchip forums.  Apparently the BM70 firmware is "difficult."
https://www.microchip.com/forums/FindPost/1016490

 

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Advantage BM70 and BM71 is the full industrial temperate range (to -40C)

RN4870-I, RN4871-I cover the complete industrial temperature range but only with the on-board chip antenna.

  • transparent UART is 10 kbps (iOS®9) max

(with thanks)

Disadvantage BM70 and BM71 is no ASCII interface.

https://www.microchip.com/design-centers/wireless-connectivity/bluetooth

 

Edits: ASCII, strikethru

 

"Dare to be naïve." - Buckminster Fuller

Last Edited: Wed. Nov 21, 2018 - 12:27 PM
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Cliff, I remember the 300 baud modem I plugged into my phone line at home to talk to the main frame (yes I remember mainfrains too), but i just entered a phone number and I was connected.  Never got into the communications stuff.  Just wrote my scientific C code, and never learned anything else.  Now I am way behind the curve, but think I understand the AT protocol now.

 

Thanks all.

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Is there not a school of thought that AT meaning attention was a backronym and that AT was chosen to be easy to auto baud on.

 

Upper case A being the longest period of zeros that can happen in any 7 bit letter and that T was a stream of transitions 10101 that was the same length as the zero period in the A.

 

That might be an urban legend though seeing as there may have not been a reason to autobaud if everyone was stuck at 300.  I don't know.

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andrewm1973 wrote:

Upper case A being the longest period of zeros that can happen in any 7 bit letter and that T was a stream of transitions 10101 that was the same length as the zero period in the A.

 

So A is 01000001 and T is 01010100.

 

Why not use '@U' ... 01000000 01010101?

#1 This forum helps those that help themselves

#2 All grounds are not created equal

#3 How have you proved that your chip is running at xxMHz?

#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Because A is ODD so the first bit transmitted is a ONE.  You can then use the length of the low time of the start bit to calculate 1T.  (Read up about autobaud routines - they all want to use odd values of which @ is not)

 

You then have a 5T low period to measure.

 

T then gives you a 10101 sequence which takes the same time (5T) as the low period in the middle of the A (as stated previously) plus gives you several more 1T for good measure.

 

This all removes ambiguity.

 

As I said above - maybe it is urban legend - but it is a fortunate combination "AT" that it has those characteristics to remove ambiguity that will reject false measurements on other random chars at other baud rates.

 

Maybe I am showing too much respect to the people that developed the modem standards and that the "AT" being really convenient to autobaud on was coincidence and it was just super lucky they didn't start all their command with the three letters "CMD"

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similar for iOS

Smartphone Basic Demo (Transparent UART) - Developer Help

...

[RN4870]

Software Tools

...

 

"Dare to be naïve." - Buckminster Fuller

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Is there not a school of thought that AT meaning attention was a backronym and that AT was chosen to be easy to auto baud on.

It's true that "AT" makes auto-baud easier so you may be right but my very blurred and distant memory is that there was "AT" before there was auto-baud. Or did I just dream that? Did Hayes modems really auto-baud right from the very start?

 

I know it's not definitive but Wikipedia says:

 

https://en.wikipedia.org/wiki/Ha...

 

where it uses the term "happens". Though maybe it was by clever design?

Last Edited: Wed. Nov 21, 2018 - 12:44 PM
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Since the RS-232 interface transmits least significant bit first, the according line pattern with 8-N-1 (eight data bits, no parity bit, one stop bit) is 11000001011001010101 (start and stop bits italicized) which is used as syncword.

Anyone notice the problem?

"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"Wisdom is always wont to arrive late, and to be a little approximate on first possession."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

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Laird LT1100 (part PRM240) is an alternate.

Throughput is 50Kbps with FEC or 100Kbps without FEC

2.0V .. 3.6V, 230mA peak TX, 30mA peak RX, 8mA idle, 300nA sleep

Receive sensitivity = -89dBm for BER of 10-6

Transmit power up to 23dBm

EIRP up to 29dBm by 6dBi antenna

2dBi dipole antenna range is approx 800ft (244m) indoor to 3.2mi (5.1km) outdoor

 

User Guide - LT1110 Module.pdf

(page 12, middle)

Tip: Can I implement a design using just TXD, RXD, and GND (three-wire interface)?

Yes. However, it is strongly recommended that your hardware monitor the CTS pin of the radio. CTS is taken High by the radio when its interface buffer is getting full. Your hardware should stop sending at this point to avoid a buffer overrun (and subsequent loss of data). You can perform a successful design without monitoring CTS. However, you need to take into account the amount of latency the radio adds to the system, any additional latency caused by retries, how often you send data, non-delivery network timeouts, and interface data rate. Laird can assist in determining whether CTS is required for your application.

via  LT1110 Series | LairdTech

 

"Dare to be naïve." - Buckminster Fuller

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joeymorin wrote:

Since the RS-232 interface transmits least significant bit first, the according line pattern with 8-N-1 (eight data bits, no parity bit, one stop bit) is 11000001011001010101 (start and stop bits italicized) which is used as syncword.

Anyone notice the problem?

 

Whoever wrote that needs to brush up on the polarity of start and stop bits I think.

 

@clawson

 

I am way too young to have heard any of the stories first hand - but I had heard it was by clever design.

 

It can be used in 7 or 8 bit systems.  It has the longest period possible to measure (5T) while still being ODD for start bit measurement.  That long measurement is an odd number of T which when coupled with the 5 1T transitions in the second byte help eliminate false positive on incorrect baud rates.

 

It is kinda like when your thinking "WTF is it with the colour burst being 3.57/4.43" and then one day you find out WHY they chose that and you realise old timey engineers are much smarter than you.

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The following arrived today at Microchip Developer; the listed Bluetooth 5 module is BM70.

Android™ Bluetooth® Low Energy (BLE) App Development For BM70 / RN4870 - Developer Help

(bottom of 3rd paragraph, 4th paragraph)

The BM70/RN4870 module acts as a BLE peripheral which can discover, connect, and communicate with the Android app.

The MCHPTransparentUART Android Studio app package is provided with this help guide. This app runs on the Android OS and connects and communicates with a BM70/RN4870 BLE module using the Microchip Transparent UART Service. Android Studio 3.2, with compile SDK version API 28 (Android 9.0 Pie), was used for the app at the time of creation. A user must migrate as needed for newer versions of Android Studio and API levels to be up to date. The BLE APIs discussed as part of this document are from Android API level 21 and up. The BLE APIs in Android API levels lower than 21 are not discussed.

 

...

 

[BOM : hardware : BM70, Bluetooth 4.0 and sub, Android 5.2 and sub; software : Android Studio, MCHPTransparentUART, terminal emulator]

 

...

Android Service for BLE - Developer Help

 


BM70 - Bluetooth Module

 

"Dare to be naïve." - Buckminster Fuller

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"Dare to be naïve." - Buckminster Fuller

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Obviously an old thread, but as I read through it the OP mentioned his goal was:

 

BTW, what I plan to use it for is remote data acquisition in a University lab where the experiment cannot have anyone near it (x-ray hazard).

At which point I so much want to say: "And what could possibly go wrong?"

 

Which, coupling Xrays and firmware, immediately brings to mind:

 

Wiki Therac-25 Disaster

 

Which, in closing, brings up George Santayana's saying, loosely quoted as: "Those who don't remember / learn from history are destined to repeat it"

 

JC

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With the Therac, the xrays weren't the root cause - bad design and implementation was the issue. I wonder if the 737 max is going to steal the Therac’s crown as most dangerous embedded system implementation?