I am using an ATtiny85 8 pin AVR to send AT commands to an RN42 Bluetooth module. I am programming the AVR using an Arduino as an ISP therefore writing the code in the Arduino IDE, using the SoftwareSerial library as the AVR has no UART port.
To ensure accurate clocking out of the data I have added an 8MHz oscillator (LFSPXO018045) on pin 2 but I'm not sure how to make sure the AVR is using this and not just defaulting to the internal osc. I've seen mention of "Fuses" that need setting? Is there any in-code things I need to do like set a register flag or any pre-scalers?
Here is the Eagle circuit and option I found so far but don't know if there's anything else that needs doing too?: PCB & IDE
By the way this is my first question so please be lenient if I've missed something!
Clock settings of AVR MCUs can be changed via using the dedicated Fuse bits. These Fuse bits unfortunately cannot be modified from software. The only way to program the Fuse bits is either using a JTAG programmer or an ISP programmer (like: USBasp, AVRISP mkII or you can use an Arduino as an ISP programmer with the right sketch on it).
This AVR Fuse calculator tool can be used to determine what settings and Fuse values you need to program.
is it possible to upload a firmware to an ATMEGA328P aka Arduino Uno using a serial terminal like Putty or Coolterm?
I know that the Arduino is ready to receive a new firmware after a reset over USB, does the IDE (and avrdude) makes something different other than echoing the binary hex file over serial port?
Thanks
Theoretically, yes. It would be awkward, and you'd need to be able to send and receive arbitrary bytes within a strict time limit, before the bootloader gives up waiting, but you could do it.
The most common bootloaders for the atmega328 use Atmel's STK500 protocol, originally designed for their own AVR development boards but widely used elsewhere (such as on the Arduino). Documentation for this protocol can be found here.
Note that Optiboot, used on modern Arduinos, implements only a subset of this protocol.
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.
i am using arduino isp to program a ATtiny2313 avr microcontroller.
Here is the probelm,
when i was programming the avr chip using the default fuse values, everything worked just fine.
But then, i changed the fuse bytes as i wanted to use an external 16 MHz crystal.
When i changed the lfuse value from 0x64 to 0xff (as per the calculation of the fuse bits), the microcontroller stopped responding.
Now everytime i try to program the microcontroller using arduino uno isp, i get an error message :
avrdude: Yikes! Invalid device signature.
avrdude: Expected signature for ATtiny2313 is 1E 91 0A
and then the fuse bytes shown after verification, very strangely are all set to 0x00 :
avrdude: safemode: Fuses OK (H:00, E:00, L:00)
i dont understand what the hell is happening and i have spent hours trying to figure out the probelm.
should the 16Mhz crystal be connected to the microcontroller while programming ?
PLEASE HELP !
Yes. When you change the configuration bits to use the external oscillator, the internal oscillator is no longer utilised - including during programming. The chip is just stuck in reset until it is provided with an external clock signal. When the ISP attempts to read out a value it is just seeing the data line stuck in the reset state - which is where all the 0x00 values are coming from.
Hook up the crystal or a signal generator to the CLOCKIN pin and you should be able to talk to the chip again.
Had the same issue. If you do not have an external oscillator, you can use
Arduino ISP
On PIN9 you get an osciallator signal you can put on the target on PIN XTAL1.
Saved me two 328p.
I have an Arduino 2560 and would like to send serial data to my PC. However, I am currently not using the Arduino Bootloader because I wanted to use a program that I wrote for an Atmega644 before (as far as I understood, one has to use the Arduino language when using the Bootloader?).
Does anyone know if what I am trying to do is possible with reasonable effort?
Connection to PC via 2560's serial0 does not depend on bootloader (if you plan connection when main program is running). You need 16u2 running to bridge 5V serial UART to USB or you can of course use any other option (e.g. MAX232 or so) to convert 5V UART to USB or RS232. But in case of RS232 double check baud rate error because of 16MHz crystal for particular baudrate.
2560 bootloader just implements firmware flash.