How do I address (reading/writing) the IO registers in lower IO-block (0x00 - 0x63 ) by using the STS LDS (or equvivalent) instructions only ??
Thanks
Kris
The main question is "where are those registers mapped in memory visible by STS/LDS". And the answer is in the datasheet:
If you want to change IN/OUT to LDS/STS, you have to add 0x20 offset to the address used in IN/OUT
7.5 I/O Memory
The I/O space definition of the ATmega328P is shown in Section “” on page 275. All ATmega328P I/Os and peripherals are placed
in the I/O space. All I/O locations may be accessed by the LD/LDS/LDD
and ST/STS/STD instructions, transferring data between the 32 general
purpose working registers and the I/O space. I/O registers within the
address range 0x00 - 0x1F are directly bit-accessible using the SBI
and CBI instructions. In these registers, the value of single bits can
be checked by using the SBIS and SBIC instructions. Refer to the
instruction set section for more details. When using the I/O specific
commands IN and OUT, the I/O addresses 0x00 - 0x3F must be used. When
addressing I/O registers as data space using LD and ST instructions,
0x20 must be added to these addresses. The ATmega328P is a complex
microcontroller with more peripheral units than can be supported
within the 64 location reserved in opcode for the IN and OUT
instructions. For the extended I/O space from 0x60 - 0xFF in SRAM,
only the ST/STS/STD and LD/LDS/LDD instructions can be used.For
compatibility with future devices, reserved bits should be written to
zero if accessed. Reserved I/O memory addresses should never be
written.Some of the status flags are cleared by writing a logical one
to them. Note that, unlike most other AVR®, the CBI and SBI
instructions will only operate on the specified bit, and can therefore
be used on registers containing such status flags. The CBI and SBI
instructions work with registers 0x00 to 0x1F only.The I/O and
peripherals control registers are explained in later sections.
Related
I have an RFID RC522 reader which reads 16-digit card number and a mini keyboard attached to Arduino Mega 2560 Rev3 which reads 4-digit Pin Number. Now I have attached a ESP-8266 Wi-Fi module in order to send that 16-digit card number and 4-digit pin to server for verification whether it is valid card user. So now I want to send both card number and pin to server at once to make less number of requests to server.
Now I want to ask that whether there’s enough memory in Arduino to store 20 digits temporarily and get a bool value from server whether it is a valid user or not.
The ATmega2560 in the Mega2560 has the following memory space :
Flash 256k bytes (of which 8k is used for the bootloader)
SRAM 8k bytes
EEPROM 4k byte
The microcontroller on the Arduino and Genuino AVR based board has EEPROM: memory whose values are kept when the board is turned off (like a tiny hard drive). This library enables you to read and write those bytes.
The supported micro-controllers on the various Arduino and Genuino boards have different amounts of EEPROM: 1024 bytes on the ATmega328P, 512 bytes on the ATmega168 and ATmega8, 4 KB (4096 bytes) on the ATmega1280 and ATmega2560. The Arduino and Genuino 101 boards have an emulated EEPROM space of 1024 bytes.
To use the specific EEPROM library use:
#include <EEPROM.h>
Examples
EEPROM Clear: Clear the bytes in the EEPROM.
EEPROM Read: Read the EEPROM and send its values to the computer.
EEPROM Write: Stores values from an analog input to the EEPROM.
EEPROM Crc: Calculates the CRC of EEPROM contents as if it was an array.
EEPROM Get: Get values from EEPROM and prints as float on serial.
EEPROM Iteration: Understand how to go through the EEPROM memory locations.
EEPROM Put: Put values in EEPROM using variable semantics.
EEPROM Update: Stores values read from A0 into EEPROM, writing the value only if different, to increase EEPROM life.
The full reference is here: https://www.arduino.cc/en/Reference/EEPROM
To summarise and answering specifically to your question, yes it is possible to store your amount of data in Arduino Mega, also using the EEPROM whose values are kept when the board is turned off (like a tiny hard drive). All the best
In this Diagram found in Wikipedia, both ROM and Program Address Register are connected to a 8-bit bus, but I thought in 8051, Internal Rom uses 16-bit adrress.
So why is the Program Address Register connected to a 8-bit bus?
Since we are not the ones who designed this architecture, we can only guess or think of reasons. If you actually want to know why, you need to find the ones who made the decision.
The 8051 multiplexes the lower address byte and the data on P0, and the upper byte of the address can go through P2. Because both bytes can be transferred at different times, an 8-bit bus suffices.
This design decision could be made to reduce silicon needs, in terms of transistors and wires. Silicon area was expensive that time.
There might be a history in the issue, too. The 8051 series followed the MCS48 (8021, 8022, 8048, etc) that had fewer address bits.
Think about the time this controller was designed, and the target market. External RAM or memory-mapped peripherals might only need 8 bits of address, just because it was enough, or too costly to use more.
Another reason might be over-simplification in the diagrams, that additionally may base one on the other. The program address register might use two 8-bit busses, each connected to one port driver block. And some "wise" guy simply put them together.
The Adress bus is not only connected there, the first 8 bits are common for address and data bus in port 0 of the microcontroller (That's why you see AD0 for the pins in pin diagram for port0, A - Address, D - Data. But in port 2 you find A0, only address), basically, an optimization to reduce the number of hardware connections, the remaining 8 bits i.e most significant bits of the address bus is in port 2 of the microcontroller so totally 8 + 8 = 16 bits.
I am trying to learn basic programming with Cheat Engine and games.
So far, I still can't grasp the pointer, particularly how to trace them.
Most of the tutorials on pointers work with 4-bytes long addresses, but what I have is 6-bytes long address. So far I have failed to track down the base address from this 6-bytes long address.
As shown in the screenshot, R9 is the offset and RCX should lead back to the pointer. R9 stays the same while RCX changing each time the game restart. Where should I go from here?
32bit Address space uses 32bit(4 Bytes) for memory addressing, while 64bit Address space uses 64bit(8 Bytes) for memory addressing.
In practice, 64bit is much, much more than required (larger than the estimated storage size of the entire internet) and hence systems have decided to use 48bit(6 Bytes) to address their memory.
Since most programming languages and computers in general only support 32bit and 64bit(do not support 48bit), the 48bit address is stored in a 64bit variable/register, with the higher most significant Bytes being zero (0x0000)
Therefore, in order to scan for the pointer value, you have to scan for an 8Byte value(with hex value being ticked as CE shows address values as hex by default)
I have a project using MDB (multi-drop bus) for vending machine (VDM).
The VDM has a MDB-RS232.
I'm not sure if it converts 9bit - 8bit (MDB-UART).
How do I read data from VDM in my computer?
Thanks all
MDB (multi-drop bus) is 9 bit, because after the standard 8 data bits (like in standard RS232 UART communication) there is a 9th bit called "mode".
(Wikipedia on MDB: "the mode bit differentiates between ADDRESS and DATA bytes.")
But you can read such data even with regular 8-bit RS232 interfaces, e.g. a plain standard USB-to-RS232 device for PC.
Here is how:
Use 9600 baud, 8 data bits, 1 stop bit, but RS232 parity setting "Space". Make sure you receive the original character value even in case of a Parity Error indication. Any MDB address byte from your VDM will be received with a Parity Error (but still be displayed correctly). Any data byte will be displayed without error.
For sending MDB ADDRESS and DATA bytes using a standard 8-bit RS232 port, you could apply temporary parity changes: Change the parity setting to "Mark" before sending an address byte, then change back to "Space" before sending data bytes.
On Windows, you can do such tricks with our Docklight software (see Docklight and MDB). It's free for basic testing and there is also a related 9-bit example project.
On Linux / Raspberry Pi other users have successfully implemented the parity trick, too, see this stackexchange post about a MDB + Pi.
But also with RealTerm, Teraterm, Termite, Bray, YAT or any other RS232 application you should be able to read the data, as long as it handles "Space" or "Mark" parity settings correctly.
You'll need an adapter which will do all convert operations on-the-fly and in real time. If you want to emulate VMC (master), you'll need MDB-UART master adapter. If you want to emulate MDB peripheral device (such as coin changer, bill validator etc), you'll need this. For two-way "sniffing" MDB bus you'll need a combination of these devices.
Direct connection PC's RS-232 to MDB will not work due to strict MDB timings (delay between VMC command and peripheral response must not exceed 5ms, delays between POLL requests are 50-300ms in general). I mean pretty reliable functioning available for commercial purposes.
I am using 2.6.32 OMAP based linux kernel. I have observed that at high speed data rate (Serial port set to 460800 baud rate) serial port HW fifo overflow happens.
The serial port is configured to generate interrupt at every 8 bytes in rx and tx both direction (i.e when the serial port HW fifo is 8 byte full serial interrupt is generated which reads the data from the serial port at once).
I am transmitting 114 bytes packet continuously (Serial driver has no clue about the packet mode, it receives data in raw mode). Based on calculations,
460800 bits/sec => 460800/10 = 46080 bytes/sec (Where 1 stop bit and 1 start bit) so in 1 second I can transmit under worst case 46080/114 => 404.21 packets without any issue.
But, I expect the serial port to handle at least 1000 packets per second as such I have configured serial driver to generate interrupt every 8 bytes.
I tried the same using windows XP and I am able to read upto 600 packets / second.
Do you think this is feasible on linux under above circumstances? or I am missing something? Let me know your comments.
could someone also, send some important configuration settings that needs to be configured in .config file. I am unable to attach .config file otherwise, I can share it.
There are two kind of overflows that can occur for a serial port. The first one is the one you are talking about, the driver not responding to the interrupt fast enough to empty the FIFO. They are typically around 16 bytes deep so getting a fifo overflow requires the interrupt handler to be unresponsive for 1 / (46080 / 16) = 347 microseconds. That's a really, really long time. You have to have a pretty drastically screwed up driver with a higher priority interrupt to trip that.
The second kind is the one you didn't consider and offers more hope for a logical explanation. The driver copies the bytes from the fifo into a receive buffer. Where they will sit until the user mode program calls read() to read them. Getting an overflow on that buffer will happen when don't configure any kind of handshaking with the device and the user mode program is not calling read() often enough. It looks exactly like a fifo buffer overflow, bytes just disappear. There are status bits to warn about these problems but not checking them is a frequent oversight. You didn't mention doing that either.
So start by improving the diagnostics, do check the overflow status bits to know what's going on. Then do consider enabling handshaking if you find out that it is actually a buffer overflow issue. Increasing the buffer size is possible but not a solution if this is a fire-hose problem. Getting the user mode program to call read() more often is a fix but not an easy one. Just lowering the baud rate, yeah, that always works.