I have a fairly complex project done on Arduino2560, which I want to port to a standalone Atmega328. My problem is that one feature in the project is that it can communicate with my computer via serial (I made a C# program to handle it on the computer side, using the COM3 port). However, Arduino uses the USB communication for a virtual serial port, and I got a bit confused about how it could be done for the Atmega. It has the RX-TX lines, but what's next? Maybe use some serial-USB converters? What's the best approach for this? Is there anything I should be careful about?
Thanks.
Considering you mention a specific port COM3 on your computer I guess we can assume you have a native RS-232 port (one of those with the sub-D9 male connector that we were used to in the old days but are not so common anymore).
If that's the case, then you can get an RS232 level shifter. You'll just have to make the connections to RX, TX, Vcc, and GND and this device will change the RS-232 voltage levels to whatever your board requires (most likely 5V or 3.3V). Some (maybe most) high-end development boards include this kind of level shifter so maybe check yours in case you already have it (if you do you'll probably see a MAX232 IC somewhere). Or if you are crafty you can also DIY.
If you prefer to connect to a USB port (then, of course, it won't be COM3unless you explicitly change the configuration on Windows Device Manager) you can go for a USB-to-serial adaptor. On that front, you have many choices, starting from the cheapest at maybe 5$, but I'd rather choose one based on the FTDI chip, which is nowadays quite ubiquitous and has proven its reliability. This one is a good example, and at the same cost as the level shifter.
Now, are there any differences between using the native RS-232 or the USB adaptor? The answer is, for most practical purposes, no. If you go to the fine details, like buffer sizes, there will be differences, but if you need to go there you'll need to study the details in both cases to see if the port you have (or the one you're planning to add) meet your needs. For most scenarios, I would choose the USB, if only because you have it everywhere (most laptops don't have a native RS-232).
All of the above (based on RS-232 and/or USB) will work fine for cables running up to 5 meters (~15 ft.) for USB or maybe 10 to 15 meters (~30-45 ft.). This should be enough for most hobbyist or at-home projects. If you want to run longer cables you'll have to go for something like RS-485.
If you choose now the USB adaptor and you think you might need to relocate your board in the future to end up more than 20 meters (15 of RS-232 + 5 of USB) away from your computer just make sure your adaptor includes a TX Enable signal (TXEN). Most adaptors based on the FTDI chip will have this signal on a pin (like the one I linked above), and that will make your life way easier if you want to use RS-485 on a two-cable half-duplex bus.
EDIT: based on the feedback below there is new info that deserves a quick update.
First, you don't have an old school RS-232 port on your PC and second you have to design the connection on the microcontroller's side.
With that in mind it's clear you have to go for the USB solution. But you need to choose if you shift both sides to RS-232 levels or you stay at TTL. That decision depends again on the length of your bus. If it'll be really short (up to 2 meters) then you can stay on TTL, otherwise better shift to RS-232 to be on the safe side. There are many people who will tell you they have much longer serial links but how reliable they are you'll never know.
Since you have to design the board, I guess it makes sense to integrate the MAX232 and a sub D-9 connector there and get the cable you mentioned for your PC.
Or, you can add only a connector on the board and get the Sparkfun level shifter I linked above for the micro's side plus the same USB to RS-232 for your PC.
Related
I'm getting interested in electronics. As a beginner thing, I wanted to try to manually turn on and off my plasma globe through Python code. The globe takes in a 5 volt DC power supply. I can power it through my laptop, which is a nitro 5. So it's sending a constant 5 volts.
I need to communicate with the USB (serial port?). The module Pyserial seems to be the right choice. However, no matter what I try it can't identify the USB serial port. Not even when I plug in a phone. I think it can only identify a COM port, whatever that is. What's the difference? In my device manager, there isn't even a COM port section.
I know it's possible to communicate through that USB port because it can send data to and from my phone, so is this simple thing even possible? Thanks!
Well, the problem is that your plasma ball has most likely not USB interface at all, meaning that from the 4 wires you maybe got inside the cable (rx; tx; GND; 5V) only the 5 volts are used inside the ball to give the HV circuit power.
Other than that, pyserial is a meant to be used for serial communication like devices with RS232 not USB interface.
If i wanted to control the ball from my computer with software i would program an AVR µc to interact via serial communication (probably with an MOS-FET as a switch), from that point on you could use for example your python module to turn it on and of.
So I'm trying to revive an old (late 90's) noise logger (Acoustic Research Labs EL-215 for those familiar) and I've been looking into USB-RS232 connectors. I have port settings from the original documentation which are as follows:
EIA RS-232-C
1200 - 19200 Baud
8 Data Bits
2 Stop Bits
Hardware Flow Control
(note: parity isn't specified)
I have an old Belkin F5U109 adapter, which hasn't worked so far - so I'm trying to work out how the Belkin is different to other USB-RS232 adapters. I also read that Prolific PL2303 and FTDI seem to be the leading USB-RS232 chipsets that nearly all modern USB-RS232 adapters seems to use.
What features should I look for in an adapter to give me the best chance of making it work with my hardware? Whats the main difference between the Prolific and FTDI chipsets?
I don't care which operating system I need to use as I'm proficient in Linux and can easily spin up a VM with VirtualBox or qemu if need be. Hardware uses DOS software, so could also run dosbox if required. Worst case I can reverse engineer the whole thing and write my own program to communicate with the EL-215, but I'd rather avoid that!
Any help much appreciated!
Edit: Here's what I've tried so far
That link seems to suggest that software flow control (XON/XOFF) doesn't work. I've investigated the device in trying to connect to and found that DTR and DSR are not connected, but RTS and CTS are. When I run the DOS software (through Windows XP on a VirtualBox VM, Belkin drivers installed, COM1 8,2, hardware flow control, no parity) which is supposed to connect with the device, I get connection error - it times out waiting for response from device.
I put the multimeter on the pins of the Belkin while using the DOS software. DTR goes from -9v to +3v momentarily, as does RTS. Obviously DTR is ignored by the device because its not connected, so RTS going high should trigger a CTS response from the device but it doesn't.
So I thought that the Belkin is perhaps waiting for DSR to go high before doing anything, so I bridged DTR to DSR, but still no response. I found it strange that DTR only momentarily goes high as if properly implemented it should stay high for the entire duration of the connection.
It's either the Belkin logic levels are not high enough (I think RS232 needs >3v to trigger) or it incorrectly implements hardware flow control. Belkin information about the adapter refers to connecting a PDA so maybe its a specific implementation for those devices...?
I have ordered FTDI and Prolific PL2303 adapters in the hopes that they might work better. Backup plan is to build a circuit to control RS232 pins individually with like an Arduino or something.
I am posting this question after not getting any sort of help across the web and reading many articles and tutorials. I ended up asking questions with hope of getting guided.
DESPERATE FOR HELP.
What i want:
1) I want to build a R/C tank.
2) Basically its not controlled by a remote control but i want control by a laptop.(i could write a c++ or c# program).
What i know:
1) I know how to develop a development board. (i want to develop my own, not use arduino)
2) I know c++ and assembly very well.
3) I know about AVR's ALU, Memories(all 3), Stack, Interrupts, IO Operations well.
4) I know theory about how SPI, RS232, UART works.
PROBLEMS: (I have many questions, but most important are)
1) B/c i have made my own board. How can i transfer my program(hex file) to my board(i seek practical and physical implementation, not theory please)(i know about a 6-pin ISP but not clear about practical implementation)
2) After it, how can i make wireless communication b/w my AVR and laptop.(hardware device?)(SPI, RS232, UART?)
MAIN CONFUSION:
1) I cannot help myself differentiating or relating SPI, RS232 and UART.
I know these are used for serial communication between devices but how?(which is used when and why and how)(appropriate hardware for transmitting device and receiving device)
THING TO KNOW:
1) I haven't started making my board and programming it because i think i should learn everything first and then do it in a one go. OR should i start practical work and things get easier automatically??
2) I learnt a tutorial series on Serial Communication from http://maxembedded.com/2013/09/serial-communication-introduction/ the starting 5 topics leaving the last one(I2C). Am i missing something there?
I hope everything is clear, and waiting for a good-men's words.
Note: I am already very misguided and lost, so i want experienced and expert's guidance. Many Many Many Many Thanks in Advance.
MY BOARD LOOKS LIKE:
http://www.robotplatform.com/howto/dev_board/schematic_l/38.jpg
1) To upload your code into AVR chip, you can use ISP interface. That requires you to connect at least 5 pins: SCK, MISO, MOSI, RESET, GND, and optionally VCC (it used to control or supply voltage, but not mandatory, if your board has it's own power supply). All you need is just to wire 6- or 10-pin ISP connector to that pins of your CPU.
To begin programming process you need to obtain some programmer device (USBasp, AVRISPmk2, STK500/600 etc.), Also, you can use Arduino board itself as ISP-programmer for external AVR chip, like this: http://www.instructables.com/id/Programming-an-ATTiny13A-using-Arduino-servo-int/
Each of programmer model requires it's compatible software (such as PonyProg), for example STK500 and AVRISP programmes could be used directly from Atmel Studio.
Also, you can connect ISP to parallel (LPT) port of the PC, and upload firmware using specialized software, such as uniprof
Another way to upload software - it is to make your own bootloader - a tiny program that will update firmware, using any available interface.
2) USART, SPI, I2C - it is different interfaces to communicate with peripherals. Note that RS232 - it is electrical interface built over USART. I.e. you need external IC which will convert USART logical level signals to RS232 electrical levels.
each of that interfaces have it's own profs and cons. And usually selection of which interface to use depends on which interface is supported by peripherals.
SPI - it is interface for high-speed communication. One master many slaves. It requires a lot of wires: MISO (data from master to slave), MOSI (data from slave to master), SCK (clock) - those three could be common for all slaves. Also it requires a SS (slave select) - one SS wire for each slave to determine which slave is in communication at the moment, also it sets the edges of the data packet.
USART - it is common interface, to communicate two chips. Each byte transmitted with foregoing start bit, optional parity and following stop bit. I.e. transfer has a quarter overhead, but byte can be transmitted in any moment.
Works in synchronous and asynchronous modes. Asynchronous mode requires only 2 wires (RX and TX, not counting GND that also required). This mode requires that receiver and transmitter to be sychronized, in most cases that required to crystal oscillator to be installed.
Synchronous mode works in the same format as asynchronous, but have additional XCK (clock) wire, that determines in which moments bits are possible to be transmitted. This allows to increase transmission speed and not requires time precision from receiver. Synchronous mode is rare used.
I2C - it's a bus with only two wires, allows many masters and many slaves. Utilizes pull-up resistors to achieve wired AND, have it's own algorithm to detect collisions, more complicated to be programmed, transmission speed is limited.
Often used by peripherals, such as accelerometers, RTCs etc.
AVR chips have no it's own support for wireless communication, therefore, to do that you need to use some external wireless chip, for example bluetooth, or WiFi, there are a lot of such modules (for example ESP8266). AVR chip communicate with them using USART, sending and receiving simple commands.
There's a old piece of software we run in our company that manages RFID cards tapping in/out to open doors.
We want to create an app who identifies who just touched in on a specific place (we have the id for that) and grab their 1st name, to say "Hi [NAME]" on a screen.
As I mentioned, the software is quite old and there are no APIs. It communicates with the RFID hardware via a serial port (COM1).
I was wondering if the best way to get the data I need is to somehow intercept the COM1 traffic and extract/look for the data I want.
Does this sound like the best way to go about it? Would it work, or would it be impossible to get names and numbers from the data being transferred?
Cheers,
Andre
Can you configure the software to use a port other than COM1, or configure the hardware so it's physical serial port is assigned to a different COM port?
If so, take a look at com0com. It's a Windows driver that creates two COM ports on your PC with a virtual NULL modem between them. Data going in on one side comes out on the other.
Here's how you'll set things up:
RFID Reader connected to physical COM port (COMx)
your program bridging COMx to COMy and sniffing the traffic
com0com linking COMy (for your program) to virtual COM1 (for the legacy software)
legacy software
You'll need to write a program to pass data between COMx and COMy while monitoring it for the information you're looking for. Make it simple yet robust, since if it goes down you're reader will stop working.
A Simpler Solution
If you only need to monitor one side of the communications, create a cable that connects the GND and RX pin of COM1 to another COM port. Now your program can monitor that side of the conversation, without interfering with the legacy software.
Well, generally, you can look at RS232 signals, if that's the way you want to do it. It's tricky because you need to "sniff" the signals, which means buying or making a rig that allows the original signals to go through, and then gives you a way to attach to them as well. And, you need to send the transmit and the receive signals to TWO serial ports (on the RX lines). Then you'll probably want to get some "sniffing" software that allows you to look at what you're getting in time sequence (ideally, with time-stamps). Some cutesy protocols also will use modem lines, so you may need to monitor those as well.
Or, try searching for "free serial port monitor" or "serial sniffer".
Good luck!
What I have in mind is having a number of sensors (temperature, accelerometer, sound level meter) that are controlled by a micro controller. What I want to do is take this information and transmit it wireless to a laptop that will take this information and put it on to a web server using Zigbee. I don't know where to start.
Since you don't have any hardware as of yet, you might want to give the Arduino a try. The hardware is affordable, can be connected to your system via USB while being programmable in-system.
The basic board can be extended via so called "shields", which offer additional features. In your case, the XBee shield would be appropriate. Connecting your laptop to a XBee module is as simple as using Sparkfun's breakout board and a mini-USB cable.
The Arduino has a large community, so you will find a lot of resources, like books, online material, example code etc.
We also provide wireless modules that can be used for serial data transmission. They can be found at www.starmanelectric.com Our modules are very similar to the xbee, but more plug and play. They can be a great for going wireless for the first time. Our devices are designed to function like a "wireless cable" so if you're used to using wires then you'll be up and running in no time at all. We also have circuit examples for transmitting to a laptop serial port or USB. Any micro-controller will be fine for this application, as long as it has a serial port and a few ADCs to sample your data. Our modules also provide simple analog in/out which can run in parallel to the serial. If you want to compare to other systems, I would google "wireless serial modules"
Regards,
Michael
Starman Electric