StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
primarykey
Id
20009416
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2013-11-15T19:50:03.923
FavoriteCount
0
LastActivityDate
2013-11-15T20:07:30.607
LastEditDate
2013-11-15T20:07:30.607
LastEditorUserId
344733
OwnerUserId
344733
ParentId
19982119
PostTypeId
2
Score
0
ViewCount
0
LastEditorDisplayName
text
Body
You can set the non-blocking flag (<code>O_NONBLOCK</code>) on the file descriptor using <code>fcntl()</code> to keep <code>read()</code> from waiting for data, but if you do that, you have to continuously poll looking for data, which is obviously bad from a CPU usage standpoint. As Charlie Burns' answer explains, the best solution is to use <code>select()</code> which will allow your program to efficiently wait until there is some data to be read on the port's file descriptor. Here's some example code taken from my own Objective-C serial port class, <a href="https://github.com/armadsen/ORSSerialPort" rel="nofollow">ORSSerialPort</a> (slightly modified): <pre><code>fd_set localReadFDSet; FD_ZERO(&localReadFDSet); FD_SET(self.fileDescriptor, &localReadFDSet); timeout.tv_sec = 0; timeout.tv_usec = 100000; // Check to see if port closed every 100ms result = select(localPortFD+1, &localReadFDSet, NULL, NULL, &timeout); if (!self.isOpen) break; // Port closed while select call was waiting if (result < 0) { // Handle error } if (result == 0 || !FD_ISSET(localPortFD, &localReadFDSet)) continue; // Data is available char buf[1024]; long lengthRead = read(localPortFD, buf, sizeof(buf)); NSData *readData = nil; if (lengthRead>0) readData = [NSData dataWithBytes:buf length:lengthRead]; </code></pre> Note that <code>select()</code> indicates that data is available by returning. So, your program will sit suspended at the <code>select()</code> call while no data is available. The program is not hung, that's how it's supposed to work. If you need to do other things while <code>select()</code> is waiting, you should put the <code>select()</code> call on a different queue/thread from the other work you need to do. <code>ORSSerialPort</code> does this.
Tags
Title
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. POOSX Serial read freeze / hang
 singulars
 PostTypePostTypeId
 PTQuestion
PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. USAndrew Madsen
UserOwnerUserId
1. USAndrew Madsen
plurals
PostLinksPostIdRelatedPostId
1. This table or related slice is empty.
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. This table or related slice is empty.
VotesPostIdCreationDate
1. This table or related slice is empty.
CommentsPostId
1. This table or related slice is empty.

Querying!

Guidance

A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.