Fix inconsitencies with openinverter_can_tool can mapping (#7)

* Don't try to erroneously setNoDelay on the WebServer

During setup() the code attempts to disable the Nagle
algorithm on a non-existent client socket which causes
an ugly error in the system log:

[   432][E][WiFiClient.cpp:320] setSocketOption(): fail on -1, errno: 9, "Bad file number"

Remove this code. If setNoDelay() needs to be set then
this needs to be done on a per-connection basis.

* Fix can mapping with negative gains and offsets

When reading can mappings the 24-bit gain value was being misinterpreted. Fix this by sign-extending the 24-bit value into a regular int32_t.

When creating a can mapping the offset field was being corrupted. Correctly mask off the gain before ORing the shifted offset value.

Tests:
 - Add can mappings with max positive and negative
    values for gain and offset.
 - Verify list displays the expected map
 - Verify with OIC that the map is as expected
 - Load a complex can map with a mix of big and little
    endian mappings with OIC and verify the
    display matches

Author: davefiddes

esp32-web-interface.ino

@@ -738,7 +738,6 @@ void setup(void){
   });
 
   server.begin();
-  server.client().setNoDelay(1);
 
   MDNS.addService("http", "tcp", 80);
 }

src/oi_can.cpp

@@ -439,8 +439,9 @@ void SendCanMapping(WiFiClient client) {
     case GAINOFS:
       if (twai_receive(&rxframe, pdMS_TO_TICKS(10)) == ESP_OK) {
         if (rxframe.data[0] != SDO_ABORT) {
-          float gain = (*(int32_t*)&rxframe.data[4]) & 0xFFFFFF;
-          gain /= 1000;
+          int32_t gainFixedPoint = ((*(uint32_t*)&rxframe.data[4]) & 0xFFFFFF) << (32-24);
+          gainFixedPoint >>= (32-24);
+          float gain = gainFixedPoint / 1000.0f;
           int offset = (int8_t)rxframe.data[7];
           DBG_OUTPUT_PORT.printf("can %s %d %d %d %d %f %d\r\n", rx ? "rx" : "tx", paramid, cobid, pos, len, gain, offset);
           JsonDocument subdoc;
@@ -497,7 +498,7 @@ SetResult AddCanMapping(String json) {
     setValueSdo(index, 1, doc["paramid"].as<uint32_t>() | (doc["position"].as<uint32_t>() << 16) | (doc["length"].as<int32_t>() << 24)); //data item, position and length
     if (rxframe.data[0] != SDO_ABORT && twai_receive(&rxframe, pdMS_TO_TICKS(10)) == ESP_OK) {
       DBG_OUTPUT_PORT.println("Sent position and length");
-      setValueSdo(index, 2, (uint32_t)((int32_t)(doc["gain"].as<double>() * 1000) | doc["offset"].as<int32_t>() << 24)); //gain and offset
+      setValueSdo(index, 2, (uint32_t)((int32_t)(doc["gain"].as<double>() * 1000) & 0xFFFFFF) | doc["offset"].as<int32_t>() << 24); //gain and offset
 
       if (rxframe.data[0] != SDO_ABORT && twai_receive(&rxframe, pdMS_TO_TICKS(10)) == ESP_OK) {
         if (rxframe.data[0] != SDO_ABORT){