firmata: add timeout for firmata_pull failing

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

include/firmata/firmata.h

@@ -111,3 +111,4 @@ int firmata_analogRead(t_firmata* firmata, int pin);
 int firmata_pull(t_firmata* firmata);
 void firmata_parse(t_firmata* firmata, const uint8_t* buf, int len);
 void firmata_endParse(t_firmata* firmata);
+void firmata_close(t_firmata* firmata);

src/firmata/firmata.c

@@ -59,6 +59,13 @@ firmata_new(const char* name)
     return (res);
 }
 
+void
+firmata_close(t_firmata* firmata)
+{
+    mraa_uart_stop(firmata->uart);
+    free(firmata);
+}
+
 int
 firmata_pull(t_firmata* firmata)
 {

src/firmata/firmata_mraa.c

@@ -24,6 +24,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <syslog.h>
 
 #include "firmata.h"
 #include "mraa_internal.h"
@@ -486,15 +487,25 @@ mraa_firmata_plat_init(const char* uart_dev)
 
     firmata_dev = firmata_new(uart_dev);
     if (firmata_dev == NULL) {
+        syslog(LOG_WARNING, "firmata: Failed to open uart to Firmata dev on %s", uart_dev);
+        fprintf(stderr, "Mraa expected to find a Firmata device on %s, is the port in use?\n", uart_dev);
         free(b);
         return NULL;
     }
 
     // if this isn't working then we have an issue with our uart
-    while (!firmata_dev->isReady) {
+    int retry = 20;
+    while (!firmata_dev->isReady && retry--) {
        firmata_pull(firmata_dev);
     }
 
+    if (!retry) {
+        syslog(LOG_ERR, "firmata: Failed to find a valid Firmata board on %s", uart_dev);
+        firmata_close(firmata_dev);
+        free(b);
+	return NULL;
+    }
+
     pthread_create(&thread_id, NULL, mraa_firmata_pull_handler, NULL);
 
     b->platform_name = "firmata";