Hardware Reference
In-Depth Information
158 static void
159 gpio_close(int pin) {
160 char buf [128];
161 FILE
f ;
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162
163 /
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164 gpio_setpath(pin,gp_unexport,buf,sizeof buf);
165 f = fopen(buf,"w");
166 assert(f);
167 fprintf(f,"%d\n",pin);
168 fclose(f);
169 }
170
171 /
Unexport : /sys/class/gpio/unexport
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172
This routine will block until the open GPIO pin has changed
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173
value.
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174
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175 static int
176 gpio_poll(int fd) {
177 struct poll fd_polls;
178 char buf[32];
179 int rc, n;
180
181 polls.fd = fd; /
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/sys/class/gpio17/value
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182 polls.events = POLLPRI; /
Exceptions
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183
184 do {
185 rc = poll (&polls,1, −1); /
Block
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186 } while ( rc < 0 && errno == EINTR );
187
188 assert(rc > 0);
189
190 lseek(fd,0,SEEK_SET);
191 n = read(fd,buf,sizeof buf); /
Read value
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192 assert(n>0);
193 buf[n] = 0;
194
195 rc = sscanf(buf,"%d",&n);
196 assert(rc==1);
197 return; /
Return value
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198 }
199
200 /
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201
Write to the GPIO pin
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202
/
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