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@ -24,17 +24,32 @@ The serial port of the computer usually meets RS-232 standard. It has signal vol
The data is transferred from these two data lines using NRZI encoding.
![2](https://user-images.githubusercontent.com/74853558/99904990-128ffa00-2cf4-11eb-8bde-f9693f8e3624.jpg)
# Data flow from USB port to FT2232H
According to USB communication protocol, data is sent through packets. It consists of 3 common packets.
![3](https://user-images.githubusercontent.com/74853558/99904992-13c12700-2cf4-11eb-96e3-813c6a7b75de.jpg)
Data field can carry varying size of data depending upon the speed at which data is transferred.
- For low speed devices, data can be upto 8B
- For full speed devices, data can be upto 1023B
- For high speed devices, data can be upto 1024B
![4](https://user-images.githubusercontent.com/74853558/99904993-1459bd80-2cf4-11eb-8905-544269d66b9f.jpg)
Data is sent through endpoint buffers within the device.
Basically, the data transaction can be done in 4 types:
- Control: It is generally used by host for sending commands and parameters.
- Interrupt: It is used by devices for sending small amounts of data. It is a polled message from the host to request specific data of the device
- Bulk: this is used by devices for sending large amounts of data.
- Isochronous: this is generally used by devices like audio channels etc, for streaming real time data.
FTDI supports bulk data transaction. Data is sent through endpoint buffers within the device. FT2232H can have a maximum packet size of 512B.
![5](https://user-images.githubusercontent.com/74853558/99904994-14f25400-2cf4-11eb-9d85-3402415096fe.jpg)
The following example code is considered to demonstrate how the data flows from one block to other. ( Image courtesy: [Shivanishah/riscv](https://github.com/shivanishah269/risc-v-core/blob/master/Images/main_ABI.png))
![14](https://user-images.githubusercontent.com/74853558/99946186-f3e53e00-2d9b-11eb-94d2-cc161b408bdc.jpg)
The example code has a bitstream of 44bytes. This is sent through data packet in data field.
![6](https://user-images.githubusercontent.com/74853558/99905235-a57d6400-2cf5-11eb-9f23-9140bd84b50f.jpg)
![7](https://user-images.githubusercontent.com/74853558/99905237-a7472780-2cf5-11eb-8387-13a4a12ac96b.jpg)