1 00:00:00,810 --> 00:00:01,280 Hello. 2 00:00:01,320 --> 00:00:01,970 Welcome back. 3 00:00:01,980 --> 00:00:07,140 In this lesson we are going to see how to configure our GPI view as an output pin. 4 00:00:08,400 --> 00:00:16,950 I'm gonna make a copy of the last project and then we continue from the core call this GPL you output 5 00:00:17,500 --> 00:00:18,110 input. 6 00:00:18,190 --> 00:00:23,990 Sorry we're going to see how to configure our key player you pin as an input. 7 00:00:24,000 --> 00:00:24,610 Right. 8 00:00:24,630 --> 00:00:25,980 We've already done output 9 00:00:33,580 --> 00:00:34,360 okay. 10 00:00:34,430 --> 00:00:35,420 They were quick to open 11 00:00:40,370 --> 00:00:43,900 to right arm to configure us on input. 12 00:00:43,910 --> 00:00:45,100 It's really simple. 13 00:00:45,110 --> 00:00:52,070 All we have to do is go to the direction register and set it as an input and then we'll have it as an 14 00:00:52,070 --> 00:00:58,680 input but for our experiment we are going to use their switches provided on the port we have switch 15 00:00:58,700 --> 00:01:06,320 one on switch to a P F for and P FS 0 respectively. 16 00:01:06,320 --> 00:01:13,430 We need to enable the um the pull up stuff for these switches so we need to enable the internal pull 17 00:01:13,430 --> 00:01:19,580 up resist the we need to enable the internal pull up resistor that are connected to these two switches 18 00:01:20,120 --> 00:01:28,020 and to enable them we can use the pin up register to enable the internal pull up resistor. 19 00:01:28,190 --> 00:01:34,160 So we have to get uh we have to create the um the address for that. 20 00:01:34,160 --> 00:01:36,200 So I'm going to come over here and create a new address. 21 00:01:36,200 --> 00:01:43,640 I've already gone ahead to get the M to get the offset of the pull up pull up read uh pull up register. 22 00:01:44,420 --> 00:02:00,470 So I'm gonna create it s also GPO F P R for pool upper register offset the offset is 0 x 5 1 0 and you 23 00:02:00,470 --> 00:02:01,990 can go and such. 24 00:02:02,480 --> 00:02:10,080 You are in your data sheet you find this offsets there so to create the um the resistor you simply build 25 00:02:10,080 --> 00:02:25,290 GPL you f p you are on the score are over here and we know we compute this by QPR you f base plus GPL 26 00:02:25,290 --> 00:02:34,090 you p you are offset that is point number 1 1 r right that's another thing we have to deal with. 27 00:02:35,910 --> 00:02:44,670 So our switch PFC row here which is switch number two it is locked by default and this means that we 28 00:02:44,670 --> 00:02:47,690 have to unlock we have to unlock this pin. 29 00:02:47,790 --> 00:02:55,480 The reason this plan is locked is because it is a B PFC row is connected to what is known as the N in 30 00:02:55,480 --> 00:02:57,110 my then non masked ball. 31 00:02:57,150 --> 00:03:03,770 Interrupt and because the the designers of the Texas Instrument microcontroller don't want us to alter 32 00:03:03,780 --> 00:03:11,040 the state of the the the pin by mistake they've locked it such that if we want to use it we've got to 33 00:03:11,130 --> 00:03:16,400 unlock it with a particular unlock key and then we can use it. 34 00:03:16,440 --> 00:03:23,070 So we've got to unlock this and to do it we need to access what is known as the lock register and then 35 00:03:23,070 --> 00:03:30,360 we write a particular unlock to this ones with unlock this we've got a comet what new set in through 36 00:03:30,360 --> 00:03:31,400 the comet right. 37 00:03:31,500 --> 00:03:33,020 Uh comets register. 38 00:03:33,180 --> 00:03:40,800 And mind you we are only doing this because we are using PSU if we connect a own switch to the M to 39 00:03:40,860 --> 00:03:42,290 the microcontroller board. 40 00:03:42,420 --> 00:03:45,730 We don't we don't need to lock in a pin if it's not locked. 41 00:03:45,900 --> 00:03:54,300 Just p f 0 has this issue or for now in our experiment it just has to do a PSU if I'm to connect a pin 42 00:03:54,300 --> 00:04:01,740 to p EF 5 I wouldn't need to unlock it I'll be good to go but because we're using PSU and internally 43 00:04:01,740 --> 00:04:08,160 is connected to the enemy we need to knock it so I'll create the register for lock in on unlocking over 44 00:04:08,160 --> 00:04:21,390 here do you play your f the registers keep a f or call it LC k 4 Look offset the offset here is 0 x 45 00:04:21,420 --> 00:04:22,420 5 2 0 46 00:04:27,510 --> 00:04:39,290 and then we can create the register self keep your f LC K on this call R E Q You would take down the 47 00:04:39,290 --> 00:04:46,610 GPL you f base and then we add this the offset 48 00:04:50,170 --> 00:04:51,010 right. 49 00:04:51,080 --> 00:04:58,440 So this one at I register once we unlock the key we've got to commit the changes and we commit to using 50 00:04:58,460 --> 00:04:59,810 the committee register. 51 00:04:59,810 --> 00:05:03,900 No no C are for short and we can create that as well. 52 00:05:03,950 --> 00:05:14,230 Oh c GPL you f c r offset it can you. 53 00:05:14,700 --> 00:05:30,500 This is or x 5 to 4 and then GPL you f c r underscore R E Q You Cooper you f space address 54 00:05:34,010 --> 00:05:41,690 plus the C are offset. 55 00:05:43,410 --> 00:05:44,280 Right. 56 00:05:44,280 --> 00:05:45,390 So this is it. 57 00:05:45,900 --> 00:05:53,130 So the key the lock key the key to to unlock code port f I'm gonna create a symbolic name to hold this 58 00:05:53,310 --> 00:06:03,740 hexadecimal value and that this can be found in the data sheet as well call this lock key. 59 00:06:05,400 --> 00:06:07,830 This is this value here. 60 00:06:09,800 --> 00:06:10,300 Right. 61 00:06:12,060 --> 00:06:14,590 So I think the set 62 00:06:17,250 --> 00:06:23,550 let's create some symbolic names to correspond to the um the bits of our switch one is switch switch 63 00:06:23,550 --> 00:06:24,010 two. 64 00:06:24,090 --> 00:06:30,480 I'm gonna come over here come down here and say stop you one for switch one 65 00:06:33,360 --> 00:06:44,160 switch one we know is that ping for and then switch two we know this is hard to pin zero 66 00:06:55,520 --> 00:06:55,970 right 67 00:07:02,750 --> 00:07:11,600 um we can create more symbolic names um remember oh uh oh a switch is an octave low switch in and by 68 00:07:11,600 --> 00:07:18,430 default the switch is high when we press the switch it goes slow meaning if we detect that if we wrote 69 00:07:18,440 --> 00:07:26,030 the switch and it state shows that it is low it means someone is pressing it has it is caught on octaves 70 00:07:26,300 --> 00:07:29,870 octave low switch right. 71 00:07:30,350 --> 00:07:34,550 So um I'm going to put a block of comment here 72 00:07:37,400 --> 00:07:38,680 with this output 73 00:07:48,810 --> 00:07:53,140 um let's stop you one pressed 74 00:08:01,340 --> 00:08:03,830 wait let's see how do I write this. 75 00:08:04,610 --> 00:08:07,550 Okay so the output is gonna come out in the um in register. 76 00:08:07,580 --> 00:08:12,880 Iris 0 0 x 0 1. 77 00:08:13,000 --> 00:08:13,690 This will mean 78 00:08:17,830 --> 00:08:18,850 a switch 1 79 00:08:22,620 --> 00:08:24,270 so each one is pressed 80 00:08:27,150 --> 00:08:27,840 sorry bother. 81 00:08:31,680 --> 00:08:32,620 Okay. 82 00:08:32,780 --> 00:08:35,900 If our sorrow which has the output is 0 x 83 00:08:39,290 --> 00:08:41,090 1 0. 84 00:08:41,600 --> 00:08:44,840 This will mean switch to 85 00:08:48,390 --> 00:08:48,930 pressed 86 00:08:52,790 --> 00:08:56,120 if our shoe which is going to be our output register has 87 00:08:58,710 --> 00:09:02,090 0 x 0 0. 88 00:09:02,160 --> 00:09:04,710 This will mean both switches 89 00:09:08,300 --> 00:09:15,960 are pressed if our 0 0 0 x 1 1. 90 00:09:15,960 --> 00:09:16,650 This will mean 91 00:09:20,820 --> 00:09:23,070 no switch is pressed. 92 00:09:23,070 --> 00:09:24,780 Remember we said it's active low 93 00:09:27,450 --> 00:09:28,670 right. 94 00:09:28,710 --> 00:09:36,210 So this is a comment so I'm going to highlight this and comments for your explanation. 95 00:09:36,210 --> 00:09:41,630 Okay I'm gonna create symbolic names to hold these state. 96 00:09:42,510 --> 00:09:56,370 So come over here I'll s top you one on the score prized and there's a Q You 0 x 0 1 and then I stop 97 00:09:56,380 --> 00:10:05,480 you too on a score pressed this AQ you score x 1 0. 98 00:10:05,680 --> 00:10:14,600 This both pressed AQ you sure x. 99 00:10:14,620 --> 00:10:18,760 Sure sure this no press 100 00:10:21,650 --> 00:10:26,830 AQ you sure x 1 1 right. 101 00:10:26,840 --> 00:10:31,130 So now we have all the registers and symbolic names we need. 102 00:10:31,720 --> 00:10:32,540 Yeah. 103 00:10:33,010 --> 00:10:38,080 So how about we continue in the next lesson this implement our code in the next lesson. 104 00:10:38,080 --> 00:10:38,640 I'll see you there.