Make it easier/possible to change channel for espnow. (#2156)

We were seeing "Peer channel is not equal to the home channel" errors.

Also see https://esp32.com/viewtopic.php?t=18291

examples/espnow.toit

@@ -15,10 +15,8 @@ import esp32.espnow
 PMK ::= espnow.Key.from-string "pmk1234567890123"
 
 main:
-  service := espnow.Service.station --key=PMK
-  service.add-peer
-      espnow.BROADCAST-ADDRESS
-      --channel=1
+  service := espnow.Service.station --key=PMK --channel=1
+  service.add-peer espnow.BROADCAST-ADDRESS
   task:: send-task service
   task:: receive-task service
 

lib/esp32/espnow.toit

@@ -107,18 +107,23 @@ class Service:
   send-mutex_/monitor.Mutex ::= monitor.Mutex
   resource_ := ?
   state_ := ?
+  channel/int := ?
 
   /**
   Constructs a new ESP-Now service in station mode.
 
   The $rate parameter, if provided, must be a valid ESP-Now rate constant. See
     $RATE-1M-L for example. By default, the rate is set to 1Mbps.
+
+  The $channel parameter must be a valid Wi-Fi channel number.
   */
-  constructor.station --key/Key? --rate/int?=null:
+  constructor.station --key/Key? --rate/int?=null --.channel=6:
+    if not 0 < channel <= 14: throw "INVALID_ARGUMENT"
+
     key-data := key ? key.data : #[]
     if rate and rate < 0: throw "INVALID_ARGUMENT"
     if not rate: rate = -1
-    resource_ = espnow-create_ resource-group_ STATION_ key-data rate
+    resource_ = espnow-create_ resource-group_ STATION_ key-data rate channel
     state_ = ResourceState_ resource-group_ resource_
 
   close -> none:
@@ -136,6 +141,9 @@ class Service:
   /**
   Sends the given $data to the given $address.
 
+  Unless the $address is a broadcast address, the $address must be a peer added
+    with $(add-peer address --key). The $address must be a valid MAC address.
+
   The $data must be at most 250 bytes long.
   Waits for the transmission to complete.
   */
@@ -166,10 +174,19 @@ class Service:
       address := Address result[0]
       return Datagram address result[1]
 
+  /**
+  Deprecated. Use $(add-peer address --key) without any channel. The channel is
+    now set during construction of the service (see $Service.station).
+  */
   add-peer address/Address --channel/int --key/Key?=null -> bool:
-    if not 0 <= channel <= 14:
-      throw "ESP-Now channel range must be 0-14"
+    return add-peer address --key=key
+
+  /**
+  Adds a peer with the given $address and $key.
 
+  The channel of the peer is set to the channel of the service.
+  */
+  add-peer address/Address --key/Key?=null -> bool:
     key-data := key ? key.data : #[]
     return espnow-add-peer_ resource_ address.mac channel key-data
 
@@ -181,7 +198,7 @@ SEND-DONE-STATE_ ::= 1 << 1
 espnow-init_:
   #primitive.espnow.init
 
-espnow-create_ group mode pmk rate:
+espnow-create_ group mode pmk rate channel:
   #primitive.espnow.create
 
 espnow-close_ resource:

src/primitive.h

@@ -707,7 +707,7 @@ namespace toit {
 
 #define MODULE_ESPNOW(PRIMITIVE)             \
   PRIMITIVE(init, 0)                         \
-  PRIMITIVE(create, 4)                       \
+  PRIMITIVE(create, 5)                       \
   PRIMITIVE(close, 1)                        \
   PRIMITIVE(send, 3)                         \
   PRIMITIVE(send_succeeded, 1)               \

src/resources/espnow_esp32.cc

@@ -403,7 +403,7 @@ PRIMITIVE(init) {
 }
 
 PRIMITIVE(create) {
-  ARGS(EspNowResourceGroup, group, int, mode, Blob, pmk, int, rate);
+  ARGS(EspNowResourceGroup, group, int, mode, Blob, pmk, int, rate, int, channel);
 
   wifi_phy_rate_t phy_rate = WIFI_PHY_RATE_1M_L;
   if (rate != -1) {
@@ -439,6 +439,11 @@ PRIMITIVE(create) {
   group->register_resource(resource);
   proxy->set_external_address(resource);
 
+  esp_err_t err = esp_wifi_set_channel(channel, WIFI_SECOND_CHAN_NONE);
+  if (err != ESP_OK) {
+    return Primitive::os_error(err, process);
+  }
+
   return proxy;
 }
 

tests/esp32/espnow1-board1.toit

@@ -22,11 +22,9 @@ import expect show *
 import .espnow1-shared
 
 main:
-  service ::= espnow.Service.station --key=PMK
+  service ::= espnow.Service.station --key=PMK --channel=CHANNEL
 
-  service.add-peer
-      espnow.BROADCAST-ADDRESS
-      --channel=CHANNEL
+  service.add-peer espnow.BROADCAST-ADDRESS
 
   print "Listening for messages."
   with-timeout --ms=10_000:

tests/esp32/espnow1-board2.toit

@@ -10,11 +10,9 @@ import esp32.espnow
 import .espnow1-shared
 
 main:
-  service ::= espnow.Service.station --key=PMK
+  service ::= espnow.Service.station --key=PMK --channel=CHANNEL
 
-  service.add-peer
-      espnow.BROADCAST-ADDRESS
-      --channel=CHANNEL
+  service.add-peer espnow.BROADCAST-ADDRESS
 
   TEST-DATA.do:
     service.send