Revision 0:9b0b3bdf816e, committed 2015-02-18

Comitter:

lzzcd001

Date:

Wed Feb 18 14:48:30 2015 +0000

Commit message:

Extra problem 2 for HW 1

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Wed Feb 18 14:48:30 2015 +0000
@@ -0,0 +1,20 @@
+#include "mbed.h"
+// This program will blink LED1 and LED4
+// using assembly language for LED1 and
+// API functions for LED4
+// declare external assembly language function (in a *.s file)
+extern "C" int my_asm();
+// declare LED outputs – let C set them up as output bits
+DigitalIn sw(p5);
+DigitalOut led(p10);
+DigitalOut myled1(LED1);
+DigitalOut myled4(LED4);
+ 
+int main() {
+    // loop forever
+    while(1) {
+      //call assembly language function to control LED1
+      my_asm();
+      wait(0.2);
+    }
+}
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Wed Feb 18 14:48:30 2015 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/4fc01daae5a5
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/my_asm.s	Wed Feb 18 14:48:30 2015 +0000
@@ -0,0 +1,35 @@
+    AREA asm_func, CODE, READONLY
+; Export my_asm function location so that C compiler can find it and link
+    EXPORT my_asm
+my_asm
+;
+; ARM Assembly language function to set LED1 bit to a value passed from C   
+; LED1 gets value (passed from C compiler in R0)
+; LED1 is on GPIO port 1 bit 18
+; See Chapter 9 in the LPC1768 User Manual
+; for all of the GPIO register info and addresses
+; Pinnames.h has the mbed modules pin port and bit connections
+;
+
+
+; Load GPIO Port 0 base address in register R1 
+    LDR     R1, =0x2009C000 ; 0x2009C000 = GPIO port 0 base address
+; Load input
+    LDR R3, [R1, #0x14]
+    AND R3, #0x0200
+
+; Load GPIO Port 0 base address in register R1 
+    LDR     R1, =0x2009C000 ; 0x2009C000 = GPIO port 0 base address
+; Move bit mask in register R2 for bit 1 only
+    MOV.W   R2, #0x000002   ; 0x000002 = 1<<1 all "0"s with a "1" in bit 1
+; value passed from C compiler code is in R0 - compare to a "0" 
+    CMP     R3, #0          ; value == 0 ?
+; (If-Then-Else) on next two instructions using equal cond from the zero flag
+    ITE EQ
+; STORE if EQ - clear led 1 port bit using GPIO FIOCLR register and mask
+    STREQ   R2, [R1,#0x1C]  ; if==0, clear LED1 bit
+; STORE if NE - set led 1 port bit using GPIO FIOSET register and mask
+    STRNE   R2, [R1,#0x18]  ; if==1, set LED1 bit
+; Return to C using link register (Branch indirect using LR - a return)
+    BX      LR
+    END
\ No newline at end of file