Adds chip select delay option

Author: johnnyman727

node/tessel-export.js

@@ -917,6 +917,8 @@ Tessel.SPI = function(params, port) {
 
   this.chipSelectActive = params.chipSelectActive === 'high' || params.chipSelectActive === 1 ? 1 : 0;
 
+  this.chipSelectDelay = (params.chipSelectDelayUs/1e3) || 0;
+
   if (this.chipSelectActive) {
     // active high, pull low for now
     this.chipSelect.low();
@@ -969,11 +971,21 @@ Tessel.SPI = function(params, port) {
 };
 
 Tessel.SPI.prototype.send = function(data, callback) {
-  this._port.cork();
+
   this.chipSelect.low();
-  this._port._tx(data, callback);
-  this.chipSelect.high();
-  this._port.uncork();
+
+  setTimeout(() => {
+    // Only cork if we have specified a target delay, otherwise delay increases
+    if (this.chipSelectDelay > 0) {
+      this._port.cork();
+    }
+    this._port._tx(data, callback);
+    this.chipSelect.high();
+    if (this.chipSelectDelay > 0) {
+      this._port.uncork();
+    }
+  }, this.chipSelectDelay);
+
 };
 
 Tessel.SPI.prototype.disable = function() {
@@ -984,19 +996,36 @@ Tessel.SPI.prototype.disable = function() {
 };
 
 Tessel.SPI.prototype.receive = function(data_len, callback) {
-  this._port.cork();
+
   this.chipSelect.low();
-  this._port._rx(data_len, callback);
-  this.chipSelect.high();
-  this._port.uncork();
+
+  setTimeout(() => {
+    // Only cork if we have specified a target delay, otherwise delay increases
+    if (this.chipSelectDelay > 0) {
+      this._port.cork();
+    }
+    this._port._rx(data_len, callback);
+    if (this.chipSelectDelay > 0) {
+      this._port.uncork();
+    }
+  }, this.chipSelectDelay);
 };
 
 Tessel.SPI.prototype.transfer = function(data, callback) {
-  this._port.cork();
+
   this.chipSelect.low();
-  this._port._txrx(data, callback);
-  this.chipSelect.high();
-  this._port.uncork();
+
+  setTimeout(() => {
+    // Only cork if we have specified a target delay, otherwise delay increases
+    if (this.chipSelectDelay > 0) {
+      this._port.cork();
+    }
+    this._port._txrx(data, callback);
+    this.chipSelect.high();
+    if (this.chipSelectDelay > 0) {
+      this._port.uncork();
+    }
+  }, this.chipSelectDelay);
 };
 
 Tessel.UART = function(port, options) {
@@ -1509,7 +1538,7 @@ function getWifiInfo() {
           if (bcastMatches === null) {
             recursiveWifi(network);
           } else {
-            // Successful matches will have a result that looks like: 
+            // Successful matches will have a result that looks like:
             // ["Bcast:0.0.0.0", "Bcast", "0.0.0.0"]
             if (bcastMatches.length === 3) {
               network.ip = bcastMatches[2];

node/test/unit/tessel.js

@@ -2354,7 +2354,10 @@ exports['Tessel.SPI'] = {
       return this.socket;
     }.bind(this));
 
-    this.tessel = new Tessel();
+    // We want to disable other ports so that we can pass around mock data.
+    // Otherwise, port A and B get 'readable' events without having any
+    // queued callbacks (because they are queued on the port we create below).
+    this.tessel = new Tessel({ ports: {A: false, B: false} });
 
     this.cork = sandbox.stub(Tessel.Port.prototype, 'cork');
     this.uncork = sandbox.stub(Tessel.Port.prototype, 'uncork');
@@ -2432,6 +2435,59 @@ exports['Tessel.SPI'] = {
     test.ok(this.spiDisable.calledOnce, true);
 
     test.done();
+  },
+  chipSelectDelayOptions: function(test) {
+    test.expect(2);
+
+    var delayUs = 10000;
+    var usToMs = 1000;
+
+    var s1 = new this.port.SPI();
+
+    var s2 = new this.port.SPI({chipSelectDelayUs: delayUs});
+
+    test.equal(s1.chipSelectDelay, 0);
+
+    test.equal(s2.chipSelectDelay, delayUs/usToMs);
+
+    test.done();
+  },
+  chipSelectDelayFunctionality: function(test) {
+    test.expect(2);
+
+    var delayUs = 10000;
+    var usToMs = 1000;
+
+    var s1 = new this.port.SPI({chipSelectDelayUs: delayUs});
+
+    var timeoutSpy = sandbox.spy(global, 'setTimeout');
+
+    s1.transfer(new Buffer(1), () => {
+      // One timeout called within transfer and one in the test below
+      test.equal(timeoutSpy.callCount, 2);
+      // The first call (chip select delay) waited an appropriate amount of time)
+      test.equal(timeoutSpy.getCall(0).args[1], delayUs/usToMs);
+      // Restore setTimeout
+      timeoutSpy.restore();
+      test.done();
+    });
+
+    // Wait until after the chip select delay has passed
+    // and the callback was enqueued. Only return data on the first request
+    setTimeout(() => {
+      var called = false;
+      this.socket.read = () => {
+        if (called) {
+          return new Buffer([]);
+        }
+        called = true;
+
+        return new Buffer([0x84, 0x1]);
+      };
+
+      // Prod the socket to read our buffer
+      s1._port.sock.emit('readable');
+    }, (delayUs / 10) * 2 );
   }
 };