From: Bob Blick <bobblick@outlook.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Sender: "piclist-bounces@mit.edu" <piclist-bounces@mit.edu>
Date: Thu, 30 Jul 2020 10:37:10 -0700
Subject: Re: [PIC] Simple GCC question
Thread-Topic: [PIC] Simple GCC question
Thread-Index: AQHWZotc+nNhZovUu0iBK4Bhj1/IWakgV02AgAAINQU=
Message-ID:
 <BYAPR02MB4055B7ACF17F19A86CA8C49BDC710@BYAPR02MB4055.namprd02.prod.outlook.com>
References:
 <BYAPR02MB405521AE3E1393B371E463FDDC710@BYAPR02MB4055.namprd02.prod.outlook.com>,
	<CAHFNz9K7LVg=L25mYPVh16nSvf2EEH_+A6_tssvKGgRE1z6gWg@mail.gmail.com>
In-Reply-To:
 <CAHFNz9K7LVg=L25mYPVh16nSvf2EEH_+A6_tssvKGgRE1z6gWg@mail.gmail.com>
Reply-To: Microcontroller discussion list - Public. <piclist@mit.edu>
Accept-Language: en-US
Content-Language: en-US
X-MS-Exchange-Organization-SenderIdResult: Pass
X-MS-Exchange-Organization-PRD: mit.edu
X-MS-TNEF-Correlator:
acceptlanguage: en-US
received-spf: Pass (protection.outlook.com: domain of outlook.com designates
	40.92.40.20 as permitted sender) receiver=protection.outlook.com;
	client-ip=40.92.40.20;	helo=NAM10-BN7-obe.outbound.protection.outlook.com; 
dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=outlook.com;
	s=selector1;
	h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;
	bh=kASwxA9/j+YWVcxgnn4pC2WGOCSUaM2F5CoOxCXbwGY=;
	b=CkBtlJZbypRb6HTS9pDMW5btUV14bIg6IUGs2aLVHrbs3iGqAy3s9L1ujlo4Vskk9J+6y/X3BhWMvj+P7ZzuxT8VLHljItAeXNkNSnf6B3l/UjpE4DzHsf5/6fC93eesRg6BFKDC9VMSbk78IAy4cov9KvYQFL/NKLkcnCbJzsgIKphxlxh8gA1sPjywez5XaZUZOYT8emEXnEGZr2BdBDcxbZzXQc5i+6lD7Jn2AN7oCVl5dXC0y3jUr5Mx60ZVAynWSjImkTCiydYeyoen5icEbl09laQdV2qMhvOh6J3lj9fJft1SwOEYDysaVxA9LivrPRD2een31PqkF1h6bw==
authentication-results: spf=pass (sender IP is 40.92.40.20)
	smtp.mailfrom=outlook.com; mit.edu; dkim=pass (signature was verified)
	header.d=outlook.com; mit.edu;	dmarc=pass action=none
 header.from=outlook.com; 
errors-to: piclist-bounces@mit.edu
list-id: "Microcontroller discussion list - Public." <piclist.mit.edu>
list-post: <mailto:piclist@mit.edu>
x-beenthere: piclist@mit.edu
x-mailman-version: 2.1.6
x-topics: [PIC]
x-mime-autoconverted: from quoted-printable to 8bit by PCH.mit.edu id
	06UHbSie022654
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0

Hi Manu,

Although the LCD will not normally be driven from interrupts, if there is a=
 lockup I would like it to leave an error code on the display, which would =
need to be done from an interrupt.

I guess to make it global without errors I will need to hardcode the ports =
and pins so I get rid of the arrays that are handed to Lcd_create()

Thanks, Bob =20

________________________________________
From: piclist-bounces@mit.edu <piclist-bounces@mit.edu> on behalf of Manu A=
braham=20
Sent: Thursday, July 30, 2020 9:55 AM
To: Microcontroller discussion list - Public.
Subject: Re: [PIC] Simple GCC question

On Thu, Jul 30, 2020 at 9:57 PM Bob Blick wrote:
>
> I'm using a nice little HD44780 LCD library in an STM32 project, it works=
 great but I'm stuck with a variable scope problem that I can only seem to =
make worse because GCC is a bit stricter than I want it to be at this point=
.. Sorry if the code example doesn't wordwrap properly.
>
> If, somewhere in main() I create an instance of the LCD like this:
>   Lcd_PortType ports[] =3D {LCD_D4_GPIO_Port, LCD_D5_GPIO_Port, LCD_D6_GP=
IO_Port, LCD_D7_GPIO_Port};
>   Lcd_PinType pins[] =3D {LCD_D4_Pin, LCD_D5_Pin, LCD_D6_Pin, LCD_D7_Pin}=
;
>   Lcd_HandleTypeDef lcd =3D Lcd_create(ports, pins, LCD_RS_GPIO_Port, LCD=
_RS_Pin, LCD_EN_GPIO_Port, LCD_EN_Pin, LCD_4_BIT_MODE);
>

Why I dislike opaque datatypes...

Instead of copying objects to Lcd_create(), a pointer could have been used,
storage could have been global, made static ..
the variables appear to be for configuration purposes ?

One way to do is make the lcd object global.

Another way is to pass a lcd object pointer to whatever function you
are calling,
unless you need to access the lcd object from interrupt context.
If you need access from interrupt context, the easier way is to have
global storage.

--

--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.