Servo.h should define MAX_SERVOS

[cburn]

Basic Infos

• [x ] This issue complies with the issue POLICY doc.
• [x ] I have read the documentation at readthedocs and the issue is not addressed there.
• [ x] I have tested that the issue is present in current master branch (aka latest git).
• [ x] I have searched the issue tracker for a similar issue.
• [ x] If there is a stack dump, I have decoded it.
• [x ] I have filled out all fields below.

Platform

• Hardware: [Feather HUZZAH ESP8266]
• Core Version: [2.6.3]
• Development Env: [Arduino IDE]
• Operating System: [MacOS]

Settings in IDE

• Module: [Adafruit Feather HUZZAH ESP8266]
• Flash Mode: [other]
• Flash Size: [4MB/0.5MB]
• lwip Variant: [v2 Lower Memory]
• Reset Method: [rts]
• Flash Frequency: [40Mhz]
• CPU Frequency: [80Mhz]
• Upload Using: [USB/SERIAL]
• Upload Speed: [115200]

Problem Description

libraries/Servo/src/Servo.h should define MAX_SERVOS with the maximum number of servos the board can control.

The standard Arduino Servo library defines this here - https://github.com/arduino-libraries/Servo/blob/2e973f62ed4a3807d228a95eb241dd5c673767d2/src/Servo.h#L88

The firmata library uses this define to test for servo capability - https://github.com/firmata/arduino/blob/0b5236938ea8a9fd5ff8a50c503549276dd5e855/examples/StandardFirmataWiFi/StandardFirmataWiFi.ino#L170

Without this defined, the firmata library doesn't allow any servo control.

MCVE Sketch

From Arduino ISP, flash the Examples/Firmata/StandardFirmataWifi sketch to the board.

Attach a servo to pin 15.

Using node.js with 'firmata' and 'etherport-client' libs installed :

var Firmata = require("firmata").Board;
var EtherPortClient = require("etherport-client").EtherPortClient;
var board = new Firmata(new EtherPortClient({
  host: "<ip of board>",
  port: 3030
}));

board.on("ready", function() {
  this.pinMode(15, this.MODES.SERVO);
  this.servoWrite(15,90);
});

Servo should move to middle position, but it doesn't.

Adding
#define MAX_SERVOS 1
to Servo.h and recompiling and flashing StandardFirmataWifi.ino works.

I would make this change and submit a PR but I don't know how to determine the maximum servos supported by this board?

Thanks.