XpressNet: next node normal inquiry is now sent after 120us timeout

device must respond within 110us according to standard, command station must wait at least 120us

src/main.cpp

@@ -42,7 +42,7 @@ int main()
   {
     TraintasticCS::process();
     XpressNet::process();
-    sleep_ms(5);
+    sleep_us(100); // FIXME: if lower, xpressnet rx fifo contains garbage
   }
 }
 

src/utils/time.hpp

@@ -0,0 +1,32 @@
+/**
+ * This file is part of the Traintastic CS RP2040 firmware,
+ * see <https://github.com/traintastic/traintastic-cs-rp2040>.
+ *
+ * Copyright (C) 2024 Reinder Feenstra
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+#ifndef UTILS_TIME_HPP
+#define UTILS_TIME_HPP
+
+#include <pico/types.h>
+
+inline bool operator>=(const absolute_time_t lhs, const absolute_time_t rhs)
+{
+  return to_us_since_boot(lhs) >= to_us_since_boot(rhs);
+}
+
+#endif

src/xpressnet/xpressnet.cpp

@@ -28,13 +28,15 @@
 #include "../traintasticcs/traintasticcs.hpp"
 #include "../utils/bit.hpp"
 #include "../utils/endian.hpp"
+#include "../utils/time.hpp"
 
 namespace XpressNet {
 
 static bool g_enabled = false;
 static uint8_t g_address;
 static uint8_t g_rxBuffer[32];
 static uint8_t g_rxBufferCount;
+static absolute_time_t g_nextNormalInquiry;
 
 static void received();
 
@@ -59,6 +61,7 @@ void enable()
 {
   g_address = 0;
   g_rxBufferCount = 0;
+  g_nextNormalInquiry = make_timeout_time_ms(1000);
 
   pio_sm_set_enabled(XPRESSNET_PIO, XPRESSNET_SM_RX, false);
   pio_sm_set_enabled(XPRESSNET_PIO, XPRESSNET_SM_TX, false);
@@ -158,6 +161,8 @@ void process()
 
   while(!pio_sm_is_rx_fifo_empty(XPRESSNET_PIO, XPRESSNET_SM_RX))
   {
+    g_nextNormalInquiry = at_the_end_of_time;
+
     uint16_t value = pio_sm_get(XPRESSNET_PIO, XPRESSNET_SM_RX) >> (32 - 9);
     if((value & 0x100) == 0) // data byte
     {
@@ -180,22 +185,25 @@ void process()
       if(checksum == g_rxBuffer[length - 1])
       {
         received();
-        g_rxBufferCount -= length;
-      }
-      else
-      {
-        g_rxBufferCount = 0; // reset buffer, checksum invalid
       }
+      g_rxBufferCount = 0;
+    }
+
+    if(g_rxBufferCount == 0)
+    {
+      g_nextNormalInquiry = make_timeout_time_us(25);
     }
   }
 
-  if(pio_sm_is_tx_fifo_empty(XPRESSNET_PIO, XPRESSNET_SM_TX))
+  if(pio_sm_is_tx_fifo_empty(XPRESSNET_PIO, XPRESSNET_SM_TX) &&
+      get_absolute_time() >= g_nextNormalInquiry)
   {
     if(++g_address > 31)
     {
       g_address = 1;
     }
     sendNormalInquiry(g_address);
+    g_nextNormalInquiry = make_timeout_time_us(120);
   }
 }