ARM9 (S3C2440) IO port -- LED water lamp

   The S3C2440A contains 130 multi-function I/O pins and they are eight ports as shown below:
– Port A (GPA): 25-bit output port
– Port B (GPB): 11-bit input/output port
– Port C (GPC): 16-bit input/output port
– Port D (GPD): 16-bit input/output port
– Port E (GPE): 16-bit input/output port
– Port F (GPF): 8-bit input/output port
– Port G (GPG): 16-bit input/output port
– Port H (GPH): 9-bit input/output port
– Port J (GPJ): 13-bit input/output port
   Each port can be easily configured by software for various system configurations and design requirements. You must define the function of each pin used before starting the main program. If the alternate function of a pin is not used, the pin can be configured as an I/O port.

IO port control register

Port Configuration Registers (GPACON to GPJCON)
   In S3C2440A, most ports are multiplexed pins. Therefore, it is necessary to decide which function is selected for each pin. PnCON (Pin Control Register) determines
which function is used for each pin.
Port Data Registers (GPADAT to GPJDAT) If the port is configured as an output port, data can be written to the corresponding bit of PnDAT. If the port is configured as an input port, data
   can be read from the corresponding bit of PnDAT . Port Pull-up Registers (GPBUP to GPJUP) The port pull-up register controls the enable/disable of pull-up resistors for each port group. When the corresponding bit is 0, the pull-up resistor of the pin is enabled. When it is 1, the pull-up resistor is disabled. If the pull-up resistor is enabled, the pull-up resistor is independent of the pin function setting (input, output, DATAn, EINTn, etc.) Miscellaneous Control Registers This register controls the sleep mode, USB pins and the data port pull-up resistor selected by CLKOUT. External Interrupt Control Register 24 external interrupts are triggered by various signal methods. The EXTINT register configures the signal trigger mode for the external interrupt request as low level trigger, high level trigger, falling edge trigger, rising edge trigger or both edge trigger. Since each external interrupt pin contains a digital filter, the interrupt control can confirm whether the request signal is longer than 3 clocks. EINT[15:0] is used for wake-up source


   

   

   
   
   

   This LED running light experiment uses GPB5-PGB8 of PB port to control 4 LEDs to light up in a cycle. It adopts common anode connection, that is, when the port bit is low level, the LED is on, and when it is high level, the LED is off.

step:

1. Initialize the IO port and set the GPBCON and GPBUP registers.

Here, GPB5-PGB8 of the PB port is used as a general IO port to realize the output function, so the GPB5-PGB8 bits of GPBCON should be 01 respectively, that is, GPBCON[17:10] is 01010101; the initial state of GPBUP is all 0, even if the pull-up resistor function is enabled, it does not need to be set, and it is set here.
The I/O port is generally connected to the peripheral device through optoelectronic isolation or other isolation devices. If it is directly connected, it must be confirmed that the load cannot exceed 4 NAND gates. Optoelectronic isolation can protect the microprocessor, perform level conversion, and distribute certain signals, so it is usually added.
2. The control idea is relatively simple. Let the 5-8 bits of the PB port cyclically become a low level (high level at other times), and the running light can be realized, and a delay is added between the two level conversions.

3. Procedure

#define rGPBCON    (*(volatile unsigned *)0x56000010)  //Port B control
#define rGPBDAT    (*(volatile unsigned *)0x56000014)  //Port B data
#define rGPBUP     (*(volatile unsigned *)0x56000018)  //Pull- up control B

#define  LED1_ON  (rGPBDAT &=~(1<<5))   //GPB5 bit cleared to 0
#define  LED1_OFF  (rGPBDAT |=(1<<5) )   //GPB5 position 1
#define  LED2_ON  (rGPBDAT &=~(1 <<6))
#define  LED2_OFF  (rGPBDAT |=(1<<6))
#define  LED3_ON  (rGPBDAT &=~(1<<7))
#define  LED3_OFF  (rGPBDAT |=(1<<7))
#define  LED4_ON  (rGPBDAT &=~(1<<8))
#define  LED4_OFF  (rGPBDAT |=(1<<8))

void Delay(void)
{
 int i;
 for(i=0;i<1000000;i++);
}

int Main()
{
 rGPBCON &=~((3<<10)|(3<<12)|(3<<14)|(3<<16));  //Clear GPBCON[10:17]
 rGPBCON |=((1<<10)|(1<<12)|(1<<14)|(1<<16));  //Set GPB5~8 as outputrGPBUP
 &=~((1<<5)|(1<<6)|(1<<7)|(1<<8));   //Set the pull-up function of GPB5~
 8rGPBDAT |=(1<<5)|(1<<6)|(1<<7)|(1<<8);    //Turn off LED
 
 while(1)
 {
  LED1_ON;Delay();LED1_OFF;
  LED2_ON;Delay();LED2_OFF;
  LED3_ON;Delay();LED3_OFF;
  LED4_ON;Delay();LED4_OFF;
 }
 return 0;
}

4. Program description: The program uses #define LED1_ON (rGPBDAT &=~(1<<5)) to set the register. Compared with the direct assignment method, this representation method is easier to observe which bit of the register has changed, and ensures that except for the bit that needs to be changed, other bits remain unchanged!