Fix for BUG #469: Bad/Empty GPS NMEA strings returned when the queries are made in a random wait iterative fashion

Fix for BUG #460:  X300: GPGGA sensor most often empty, while RMC is usually OK
- Added checksum verification of NMEA strings
- Improved handling of short or malformed strings
- Fixed GPSDO data synchronization between X300 firmware and host

1 files changed, 11 insertions, 4 deletions

diff --git a/firmware/x300/x300/x300_main.c b/firmware/x300/x300/x300_main.c
index d7fd32ac3..8717bf690 100644
--- a/firmware/x300/x300/x300_main.c
+++ b/firmware/x300/x300/x300_main.c
@@ -345,12 +345,12 @@ static void handle_uarts(void)
     static uint32_t rxoffset = 0;
     for (int rxch = wb_uart_getc(UART0_BASE); rxch != -1; rxch = wb_uart_getc(UART0_BASE))
     {
-        rxoffset = (rxoffset+1) % (NUM_POOL_WORDS32*4);
+        rxoffset++;
         const int shift = ((rxoffset%4) * 8);
         static uint32_t rxword32 = 0;
         if (shift == 0) rxword32 = 0;
-        rxword32 |= ((uint32_t) rxch) << ((rxoffset%4) * 8);
-        rxpool[rxoffset/4] = rxword32;
+        rxword32 |= ((uint32_t) rxch & 0xFF) << shift;
+        rxpool[(rxoffset/4) % NUM_POOL_WORDS32] = rxword32;
         shmem[X300_FW_SHMEM_UART_RX_INDEX] = rxoffset;
     }
 
@@ -445,17 +445,24 @@ int main(void)
         static const uint32_t tick_delta = CPU_CLOCK/1000;
         if (ticks_passed > tick_delta)
         {
-            handle_link_state(); //deal with router table update
+//            handle_link_state(); //deal with router table update
             handle_claim(); //deal with the host claim register
+handle_uarts(); //udp_uart_poll();
             update_leds(); //run the link and activity leds
+handle_uarts(); //udp_uart_poll();
             garp(); //send periodic garps
+handle_uarts(); //udp_uart_poll();
             xge_poll_sfpp_status(0); // Every so often poll XGE Phy to look for SFP+ hotplug events.
+handle_uarts(); //udp_uart_poll();
             xge_poll_sfpp_status(1); // Every so often poll XGE Phy to look for SFP+ hotplug events.
+handle_uarts(); //udp_uart_poll();
             last_cronjob = wb_peek32(SR_ADDR(RB0_BASE, RB_COUNTER));
         }
+//handle_uarts(); //udp_uart_poll();
 
         //run the network stack - poll and handle
         u3_net_stack_handle_one();
+handle_uarts(); //udp_uart_poll();
 
         //run the PCIe listener - poll and fwd to wishbone
         forward_pcie_user_xact_to_wb();