Bare Metal Notes

1.GPIO and Gate Circuit
1.1 Input, output pin, pull-up resistor, transistor

At this stage, the pins can be both output and input pins, which need to be configured appropriately when used.
The configuration pin function is read, PIN is input pin, configuration pin function is write, PIN is output pin.

Pull-up resistor (NPN transistor): function for the input pin, which can be used to determine the input status

Pull-down resistor (PNP transistor): The Development Board output 1, the dangling pin is 0, the Development Board output 1, the dangling pin is 1.

1.2 with doors, or doors, not doors
Non-gate: To make the passing current opposite the output current
With the door:
or door:

Interrupt pin: has input function and can interrupt CPU.

2. Protocol class
First, the principle is that others can understand (the agreement that the two parties agree), and secondly, cannot say too quickly (both parties meet timing requirements)
2.1 Uar (tuniveisal async receive/transmit)
Serial port out of the way: TXD0 outgoing data to the level conversion chip (in order to improve the interference resistance of transmission data, generally increase the current range) and then through the interface line to the computer rxd
Same
Asynchronous transfer: 2440 want to send data, let RXD0 0, save ts,pc feel RXD0 from 1 to 0, know 2440 to start sending data.
Baud Rate: The number of data bits transmitted in one second
Therefore, 2440 and PC in the transmission of data must be in advance to agree the baud rate (that is, a second to the number of data monitoring), data bits, stop bit. These parameters are set by using an existing software for the PC, and the Development Board needs to be set up in the serial controller.
2.2 I²c
Only two.
2.3 SPI
The construction process of digital circuit is equivalent to the process of building blocks, only the corresponding PIN can be matched.
The chip selection signal is controlled by GPIO, and the corresponding chip is selected. (Another way is to use the address to determine the chip)
2.4 NAND
I0-i7 can transmit both data and address, as well as the ability to transfer commands, which determine the mode of these ports by CLE, Ale

2.5 LCD

3. Memory-like interfaces
3.1 NOR, SDRAM, Nic
3.2 Wiring and access process of non-pass bit wide peripherals
3.3 How to determine the access address, set the memory controller

4. Schematic diagram of several development boards from beginning to end

With this girl.

Bare Metal Notes