I tested the NodeMCU firmware on 4 ESP8266 modules and I have a problem with the WiFi range of the modules (only 8 meters).
I tried to switch to the Arduino ESP8266 core firmware and voilà, the modules have a better range (>12 meters). I think that NodeMCU doesn't set the ESP8266 to the maximum power.
I looked at the Arduino code and it contains a setOutputPower method that set the RF power level of the ESP8266. How can I set this option in the NodeMCU firmware without modifying the firmware?
Higher RF power level means higher power consumption obviously. You need to balance your options should you run the device off a battery.
NodeMCU offers wifi.setphymode() to control this. The documentation gives you a nice overview how the pyh mode relates to typical power consumption.
Update 2017-11-19
There's a PR in the making that'll give you control over system_phy_set_max_tpw from the SDK: https://github.com/nodemcu/nodemcu-firmware/pull/2171
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Is there a way (or trick) to set a CH340 to 25000 baud on Linux?
If not:
Is there a better chip which is able to do that 25000 baud (no FTDI please)?
Is there a completely different and better way to achieve my goal (see below)?
Background:
I would like to interface a China Diesel heater to a Raspberry Pi (OpenPlotter on a ship).
This was done in Open Source with a uC (STM or EsP32) with http://www.mrjones.id.au/afterburner/
There is this blue wire with half duplex RS232#TTL and baud rate of 25.000 baud (8N1). This is the binary, proprietary communication interface to the heating.
I tried to use one of this china USB to RS485 adapters which use a CH340C internally.
The interface of Afterburner:
The USB to RS485 interface is similar Afterburner:
I think I should be able to use this interface without major modifications if I would use "channel B" of RS485 with a pull up resistor (worth a try).
My main problem is the baud rate at the moment. I think I will run in the same problem if I would use a CP210x. I guess a FTDI232 might be able to handle this baud rate but I will not use this chip at all.
My other idea was to use a NodeMCU (CH340 with ESP32/ESP8266) and speak 25000 baud to the heating and 28800 over the serial to USB of the NodeMCU. I think this is a little bit overkill to do it this way.
I would like to connect 2 usb webcams to a RaspberryPI and be able to get at least 1920 x 1080 frames at 10 fps using OpenCV. Has anyone done this and knows if this is possible? I am worried that the PI has only 1 usb bus?? (usb2) and might get a usb bandwidth problem.
Currently I am using an Odroid and it has a usb2 and usb3 bus so I can connect 1 camera to each without any problemo..
What i have found in the past with this is no matter what you select using OpenCV for bandwidth options the cameras try to take up as much bandwidth as they want.
This has led to multiple cameras on a single USB port being a no-no.
That being said, this will depend on your camera and is very likely worth testing. I regularly use HD-3000 Microsoft cameras and they do not like working on the same port, even on my beefy i7 laptop. This is because the limitation is in the USB Host Bandwidth and not processing power etc.
I have had a similar development process to you inthe past though, and selected an Odroid XU4 because it had the multiple USB hosts for the cameras. It also means you have a metric tonne more processing power available and more importantly can buy and use the on-board chip if you want to create a custom electronics design.
I'm wondering if I can do something like this:
Do some image processing with opencv on my pc, do some math and send data to RaspberyPi to PID controller and then control servos, in real time.
UART wolud be the best connection?
In principle you can use any means to communicate from the PC to the Raspberry PI that are available (UART, ethernet, etc.).
However, you just have to be careful about any time requirements you have in the system you are controlling and check whether the communication rate is suitable.
For instance, you can use 9600 baud UART to temperature control, as the dynamics of such systems are usually slow. If your servos control an inverted pendulum, then the communication speed might make it impossible to control.
I have researched (and learnt quite a bit), but I have little experience in programming and only really understand basic sketches so far. I would like to use the Arduino R3 (more specifically, the usb to serial converter chip) to program a full-size hobby radio.
I have connected my radio to the Arduino appropriately (5V, Rx, Tx, Gnd) and put the Arduino into Tristate mode (apparently you have to do this..), but I seem to be lacking appropriate drivers. I basically want my Arduino R3 to function exactly like this: CP2102 . Please note that I am not being super cheap. To get something like that where I live would take at the very least a month. Some people also say that I should remove the Atmega chip. The ultimate goal is that I have a device, with drivers, on a com port and not just an "unknown device".
So, my questions are: leave the Atmega on, or remove it? and which drivers do I need?
Thanks!
EDIT: I found almost exactly what I need just after I posted. For some reason I couldn't get it to work, but maybe you could help me understand? Here's the link LINK If anyone is keen to help me out!
Just to make it clear: it has been done before, but I get the feeling people leave out things which they think are obvious, but to the not-yet-professional tinkerer like me aren't :/
Thanks so much!
It seems like the links you reference are for older Arduinos with an FTDI chip. The Arduino Uno doesn't use that. Here's a link for using the Uno
So! All of the older Arduinos (NG, Diecimila and Duemilanove) have
used an FTDI chip (the FT232RL) to convert the TTL serial from the
Arduino chip (Atmel ATmega). This allows for printable debugging,
connecting to software like PureData/Max, Processing, Python, etc.
etc. It also allows updating the firmware via the serial bootloader.
The good news about the FT232RL has royalty-free drivers and pretty
much just works. The bad news is that it can -only- act as a
USB/Serial port. It can't act like a keyboard, mouse, disk drive, MIDI
device, etc.
and
The Arduino Uno has a number of facilities for communicating with a
computer, another Arduino, or other microcontrollers. The ATmega328
provides UART TTL (5V) serial communication, which is available on
digital pins 0 (RX) and 1 (TX). An ATmega16U2 on the board channels
this serial communication over USB and appears as a virtual com port
to software on the computer. The '16U2 firmware uses the standard USB
COM drivers, and no external driver is needed. However, on Windows, a
.inf file is required. The Arduino software includes a serial monitor
which allows simple textual data to be sent to and from the Arduino
board. The RX and TX LEDs on the board will flash when data is being
transmitted via the USB-to-serial chip and USB connection to the
computer (but not for serial communication on pins 0 and 1).
Basically the LINK you provided, shows the user HACKING the Arduino. Using the USB/Serial(TTL) converter(what ever chip that is on your Arduino) to link to the Radio's Mini Din connector, in place of connecting to the Arduino's CPU.
As stated in other answer the Arduino uses a CHIP (of some flavor) to bridge the USB(Virtual Serial Port) to the Serial Port of the ATmega328 micro. These pins are available on the Shields connector 0(RX) and 1(TX). Hence you see the picture wiring those pins to the Radio's DIN connector.
Where I would expect in addition the RESET of the Arduino's CPU would be held to GND, this would force the pins into Hi. Simply with an extra wire jump the RESET pin to a GND.
It's working! Somewhere along the line the drivers for my arduino seem to have been deleted, so I reinstalled them, did what you said, and learnt something.
So to clarify for others: pretty much plug and play (as the link I posted suggests), but make sure to install the arduino drivers properly.
Thanks a lot for the help!
I am very enthusiastic in writing device drivers for a microcontroller(like PIC, Atmel etc).
Since I am a newbie in this controller-coding-area I just want to know whether writing device drivers for controller is same as we write for linux( or any other OS) ?
Also can anyone suggest some online device driver building tutorial for the same ..?
Thanks,
If you are thinking about developing the device drivers to interface your device with a host computer (probably using USB), then most of the microcontrollers nowadays implement default classes that rely on native drivers.
A concrete example:
If you use a PIC18F4555, you can use the regular HID (human interface device) windows driver to communicate with your microcontroller (given you implemented it correctly). No need to develop any driver.
Writing a device driver for an MCU is a pretty far cry from writing it for a OS. Most MCUs won't have an OS running on them at all. You'll generally end up writing some low level Interrupt Service Routines (ISRs) and filling up buffers, that your application software will end up emptying. You don't have to fit into any device driver paradigm that an O/S has defined. You basically have to read the datasheet for the device you are wanting to interface with and read and write to its memory over whatever interface it might use (e.g. SPI, I2C, UART, etc.). Ultimately the device driver ought to provide intuitive function calls to the application software.
If you are using AVR MCU like atmega then you can use vusb (https://www.obdev.at/products/vusb/index.html) for those MCU that don't have any HID and handles the interrupts by connecting D+ and D- pins of the USB to digital I/O ports of the MCU.
The atmegaU2 packages have their own USB communication ports and HID.