pbio/port_lump: Send keep-alive right away.

It turns out the ColorLightMatrix needs the NACK to get going at all, so make sure we always send one before we start waiting on the timeout.

In b17e503, we removed grace period of 6 keep-alive messages to go unanswered, which was essentially masking this issue so the device worked before.

Author: laurensvalk

lib/pbio/src/port_lump.c

@@ -917,16 +917,19 @@ pbio_error_t pbio_port_lump_data_send_thread(pbio_os_state_t *state, pbio_port_l
 
     PBIO_OS_ASYNC_BEGIN(state);
 
-    pbio_os_timer_set(timer, EV3_UART_DATA_KEEP_ALIVE_TIMEOUT);
+    // Some devices need the NACK keep-alive signal before doing anything, so
+    // initially set the timer to expire soon.
+    pbio_os_timer_set(timer, 1);
 
     for (;;) {
 
         PBIO_OS_AWAIT_UNTIL(state, pbio_os_timer_is_expired(timer) || lump_dev->mode_switch.requested || lump_dev->data_set->size > 0);
 
         // Handle keep alive timeout
         if (pbio_os_timer_is_expired(timer)) {
-            // make sure we are receiving data
-            if (!lump_dev->data_rec) {
+            // Make sure we are receiving data. The first time around, we allow
+            // not having any data yet.
+            if (!lump_dev->data_rec && timer->duration == EV3_UART_DATA_KEEP_ALIVE_TIMEOUT) {
                 debug_pr("No data since last keepalive\n");
                 lump_dev->status = PBDRV_LEGODEV_LUMP_STATUS_ERR;
                 return PBIO_ERROR_TIMEDOUT;