小程序连接上佳博2120tu打印机后如何编写打印命令

连接佳博2120tu打印机后，你需要了解其支持的打印命令和指令集，通常使用ESC/POS指令集。

下面是一些打印命令的示例：

1. 打印文本

function printText(text) {
  let buffer = new ArrayBuffer(text.length)
  let dataView = new DataView(buffer)
  for (let i = 0; i < text.length; i++) {
    dataView.setUint8(i, text.charCodeAt(i))
  }
  wx.writeBLECharacteristicValue({
    characteristicId: 'xxxx',
    serviceId: 'xxx',
    value: buffer,
    success(res) {
      console.log('writeBLECharacteristicValue success', res)
    },
    fail(res) {
      console.log('writeBLECharacteristicValue fail', res)
    }
  })
}

2. 打印图片

function printImage(imageUrl) {
  wx.getImageInfo({
    src: imageUrl,
    success(res) {
      let canvas = wx.createCanvasContext('canvas')
      canvas.drawImage(res.path, 0, 0, 200, 200)
      canvas.draw(false, function() {
        wx.canvasToTempFilePath({
          canvasId: 'canvas',
          success(res) {
            wx.getImageInfo({
              src: res.tempFilePath,
              success(res) {
                wx.getFileSystemManager().readFile({
                  filePath: res.path,
                  success(res) {
                    wx.writeBLECharacteristicValue({
                      characteristicId: 'xxxx',
                      serviceId: 'xxx',
                      value: res.data,
                      success(res) {
                        console.log('writeBLECharacteristicValue success', res)
                      },
                      fail(res) {
                        console.log('writeBLECharacteristicValue fail', res)
                      }
                    })
                  }
                })
              }
            })
          }
        })
      })
    },
    fail(res) {
      console.log('getImageInfo fail', res)
    }
  })
}

3. 切纸

function cutPaper() {
  let buffer = new ArrayBuffer(2)
  let dataView = new DataView(buffer)
  dataView.setUint8(0, 0x1D)
  dataView.setUint8(1, 0x56)
  wx.writeBLECharacteristicValue({
    characteristicId: 'xxxx',
    serviceId: 'xxx',
    value: buffer,
    success(res) {
      console.log('writeBLECharacteristicValue success', res)
    },
    fail(res) {
      console.log('writeBLECharacteristicValue fail', res)
    }
  })
}

注意：以上代码中的特征值和服务UUID需要根据你的打印机型号和操作系统不同而有所调整。