I am implementing USB as a host to read the files stored in the Flashdrive. To read I implement the read(10) command in SCSI.
This command has a field called Logical Block Address, as in the address I want to read. Now, I know the sector number I want to read.
So, is the Logical Block Address and Sector Number the same?
I looked into Cylinder-Head-Sector(CHS) but I dont have information about cylinder or heads
In common usage in SCSI, a sector is the same as a Logical Block Address. It is very likely that your device has 512-byte sectors (512-byte logical blocks). There are some high-performance SSD's and large-capacity spinning media drives that have 4096-byte sectors. These drives are labelled as having "Advanced Formatting".
CHS addressing isn't supported by SCSI. So, if you somehow have just a sector number, it's probably the SCSI "sector" or logical block address.
All of those integer fields in the typical SCSI commands are in big-endian format. If you're on a typical x86 PC of some kind, your integers will be little-endian format. Before you put your sector number in the field in your READ(10) command, you'll need to convert it with htobe32() or htonl(). Likewise for the num field: (htobe16() or htons()).
Related
Context: I am following an embedded systems course https://www.edx.org/course/embedded-systems-shape-the-world-microcontroller-i
In the lecture on bit specific addressing they present the following example on a "peanut butter and jelly port".
Given you a port PB which has a base address of 0x40005000 and you wanted to access both port 4 and port 6 from PB which would be PB6 and PB4 respectively. One could add the offset of port 4(0x40) and port 6(0x100) to the base address(0x40005000) and define that as their new address 0x40005140.
Here is where I am confused. If I wanted to define the address for PB6 it would be base(0x40005000) + offset(0x100) = 0x40005100 and the address for PB4 would be base(0x40005000) + offset(0x40) = 0x40005040. So how is it that to access both of them I could use base(0x40005000) + offset(0x40) + offset(0x100) = 0x40005140? Is this is not an entirely different location in memory for them individually?
Also why is bit 0 represented as 0x004. In binary that would be 0000 0100. I suppose it would represent bit 0 if you disregard the first two binary bits but why are we disregarding them?
Lecture notes on bit specific addressing:
Your interpretation of how memory-mapped registers are addressed is quite reasonable for any normal peripheral on an ARM based microcontroller.
However, if you read the GPIODATA register definition on page 662 of the TM4C123GH6PM datasheet then you will see that this "register" behaves very differently.
They map a huge block of the address space (1024 bytes) to a single 32-bit register. This means that bits[9:2] of the the address bus are not needed, and are in fact overloaded with data. They contain the mask of the bits to be updated. This is what the "offset" calculation you have copied is trying to describe.
Personally I think this hardware interface could be a very clever way to let you set only some of the outputs within a bank using a single atomic write, but it makes this a very bad choice of device to use for teaching, because this isn't the way things normally work.
Using LOGISIM, build a working 4-nibble RAM. The RAM must have the following elements: 4 nibbles, addressing circuits, the address register, the data register, the mode register (bit), a u-bus, and a clock. Your RAM must be able to read and write nibbles.
You will run your circuit manually by setting the address, mode and data registers, then you will start the clock. The desired action will take place. For example: if you plug in an address into the address register, and a 1 in the mode register, and a nibble in the data register, and you turn on the clock, then the nibble must be copied into the RAM nibble at the desired address.
Since you have a 4-nibble RAM then you will only have addresses 00, 01, 10, and 11. Mode register set to 1 is for write and 0 is for read.
A u-bus is needed to properly handle read and write operations between the data register and the 4-nibbles of RAM.
Elements allowed:
Connectors:
- Wires
- Input connector
- Output connector (or display)
Built-in machines and gates:
- A Bit (RS, or D)
- Clock
- AND, OR, NOT, XOR, NAND, NOR
I am working on a project where I'm trying to implement I2C master-slave communication so as to read some data from a magnetic sensor. That's all OK and I have written the code. However, I am not quite sure about the slave address needed for the communication to actually happen. The board I'm using can hold STM32 ARM® Cortex™-M3 and Cortex™-M4 MCU's. I don't know if it matters, but the MCU I'm using is STM32F107VCT6.
The part of the code where I need to enter the address is in the following function marked as "SLAVE_ADDRESS_GOES_HERE":
uint8_t Magnet_readReg(const uint8_t regAdd)
{
uint8_t pom[1] = {0};
pom[0] = regAdd;
I2C1_Start();
I2C1_Write(SLAVE_ADDRESS_GOES_HERE, pom, 1, END_MODE_RESTART);
I2C1_Read(SLAVE_ADDRESS_GOES_HERE, pom, 1, END_MODE_STOP);
return pom[0];
}
The results should be some numbers which tell me how strong the magnetic field is. It has three different values as an output because it calculates a value for each of the three axes (yes, it's the correct plural of the word axis), so it can could be used as a compass for example.
Now the trick is that I don't get any results because I don't know the actual address of the sensor. Therefore, I will share the datasheet of the sensor I'm using. I am not sure if i'm reading it correctly.
Here is the datasheet:
https://www.memsic.com/userfiles/files/Datasheets/Magnetic-Sensors-Datasheets/MMC3416xPJ_Rev_C_2013_10_30.pdf
Solved.
As it turns out, there was something wrong with the board itself. Therefore, a connection couldn't be established. And the address is 60H for writing and 61H for reading. 30H is the address, but when you add a zero or a one in the LSB position you get 60H or 61H.
The I2C address of your sensor is described on page 4 of the datasheet you provided. You must read the marking on your device package, then use the table from "Number" to "Part number" in the datasheet to determine your exact part. Finally, use the table under the "Ordering Guide" to find the factory-programmed I2C slave address of your device.
Given that you later specified that your 7-bit I2C slave address is 0x30, then you must have part number MMC34160PJ, which should be marked:
0 •
XX
My problem is that I used the "read and write" example on the Arduino to re-write an RFID card (MIFARE Classic 1K) block by block. I started writing at block 4. At block 7 it stopped and now I can't read any sector. I wrote zeros to each block.
The DumpToSerial function just prints for every sector
PCD_Authenticate() failed: Timeout in communication.
It can still read the UID, the SAK, and the PICC type.
Did I destroy the card or can I recover it?
Some more info:
Card: MIFARE Classic 1K
Arduino Mega2560 from Elegoo
RC522 from the starter-kit
With MIFARE Classic 1K, every 4th block is the sector trailer (each 4 blocks are grouped into one sector). The sector trailer contains the access keys (key A on bytes 0..5, key B on bytes 10..15) and access conditions (access bits on bytes 6..8) for a sector.
The access conditions are protected by a redundancy mechanism where each access bit is present multiple times in positive and negative logic. A MIFARE Classic card allows overwriting these access conditions with invalid values (impossible combinations of access bits). However, once the access conditions are set to such an invalid value, the security logic of the chip will disable all access to the wole sector. Consequently, writing invalid access conditions to the sector trailer renders the whole sector unusable. This state is permanent and cannot be reverted.
You wrote all blocks starting at block 4 with all-zeros. Consequently, you wrote the sector trailer of sector 1 (in block 7) with the access conditions set to all-zeros. This is an invalid value for the access conditions. Therefore, sector 1 is permanently unusable. Since you indicated that you immediately received errors after writing block 7, you might be lucky and did not overwrite other sector trailers (e.g. block 11 for sector 2). In that case, those other sectors should still be usable. Similarly, since you started writing at block 4, the first sector (sector 0, blocks 0..3) should also still be accessible.
I have scales equipped with RS232 serial port and a Bluetooth transmitter. I made a program in VBA to receive data from the scales. However, lets say out of 10 incoming strings I get 3 distorted. My regular strings look like: "+001500./3 G S". This means 1500.3 grams above zero and the output is stable. But sometimes I get strings like separated like "+" or "001500./3" or "G S". When I plug serial cable I have no distortions.
Serial ports are just byte streams. You can never make assumptions about how many of the bytes will show up on each read operation. It's only coincidence that when you use a real cable you read the whole string at once. You have to do the string splitting yourself, and continue reading when you only get a partial result.