Tessel 2 - i2c.read 未记录缓冲区

Question

我正在尝试使用 Tessel 2 从 CO2 传感器读取数据，但收效甚微。

来自传感器的数据sheet:

To read the current CO2 concentration from the sensor we need to read memory locations 0x08 (hi byte) and 0x09 (low byte).

To do this we need to send a sequence of two I2C frames: first we send an I2C write frame containing the sensor address, command number and how many bytes to read, RAM address to read from, and a checksum. Then we send an I2C read frame to read the status, data and checksum.

In our case we want to read 2 bytes starting from address 0x08. This will give us data from address 0x08 and 0x09, which contains current CO2 reading. The sensor address is 0x68 (default factory setting, configurable in EEPROM).

So, the first frame should look like:

Start | 0xD0 | 0x22 | 0x00 | 0x08 | 0x2A | Stop

--a. 0xD0 is Sensor address and read/write bit. 0x68 shifted one bit to left and R/W bit is 0 (Write).

--b. 0x22 is command number 2(ReadRAM), and 2 bytes to read

--c. Checksum 0x2A is calculated as sum of byte 2, 3 and 4.

The next frame will read the actual data:

Start | 0xD1 | <4 bytes read from sensor> | Stop

--d. The 1:st byte from the sensor will contain operation status, where bit 0 tells us if the read command was successfully executed.

--e. The 2:nd and 3:rd byte will contain CO2 value hi byte and CO2 value low byte.

--f. The 4:th byte contains checksum

因此，我的代码如下所示：

'use strict';

// Require
var async   = require('async');
var tessel  = require('tessel');
var port    = tessel.port.B;

// Vars
var i2c;
   
// Process
async.waterfall([
  function(callback) {
    i2c = new port.I2C(0xD0);
    callback(null,new Buffer([0xD0, 0x22, 0x00, 0x08, 0x2A]));
  },
  function(data, callback) {
    i2c.send(data, function (error) {
        console.log("Done sending the data");
        callback(null,null);
    })
  },
  function(data, callback) {
    i2c = new port.I2C(0xD1);
    callback(null,null);
  }
], function (err, result) {
    i2c.read(4, function (error, buffer) {
        console.log(`I2C Slave (0x${address.toString(16)} response: `, buffer);
    });    
});

代码一直执行到 i2c.read 代码块，并且从不接收传感器返回的缓冲区。

我决定不使用转账方式，因为地址变了

我做错了什么？

Answer 1

我通过查看 Arduino 草图做了一点欺骗，它给了我一些最终被淘汰的想法。

i2C 应该使用正确的地址 (0x68) 进行实例化，而不是像数据表中提供的文档那样移动
i2c.send 的缓冲区不应包含地址，因为 i2c 在实例化时已经在帧中添加了地址。所以缓冲区应该是这样的：

回调（空，新缓冲区（[0x22，0x00，0x08，0x2A]））；
在发送 1000 毫秒读数之间添加超时

Tessel 2 - i2c.read 未记录缓冲区

Tessel 2 - i2c.read not logging buffer

javascript

embedded

i2c

tessel