ESP32 ARDUINO BLE getValue function cannot read 0x00 binary from app

[maozhifeng]

The ESP32 ARDUINO BLE getValue function cannot read the 0x00 data from the app.
For example, the mobile app sends: 0x01 0x02 0x00 0x03 0x05;
The esp32 getValue() function can only return 0x01 0x02 and the data after 0x00 and 0x00 will not be read. How can I solve this problem?

The mobile app I use is nRFconnect

[chegewara]

It can read, if you know how, but to make yourlife easier there is another function:
https://github.com/espressif/arduino-esp32/blob/master/libraries/BLE/src/BLECharacteristic.h#L64

[maozhifeng]

它可以读取，如果你知道如何，但为了让你的生活更轻松，还有另一个功能：https :
//github.com/espressif/arduino-esp32/blob/master/libraries/BLE/src/BLECharacteristic.h#L64

它可以读取，如果你知道如何，但为了让你的生活更轻松，还有另一个功能：https :
//github.com/espressif/arduino-esp32/blob/master/libraries/BLE/src/BLECharacteristic.h#L64

I have tried the getData function and still cannot return 0x00. It can only return the data in ascii code. Can you clearly tell me how to change it?

this is my test code:

class MyCallbacks: public BLECharacteristicCallbacks {
void onWrite(BLECharacteristic pCharacteristic) {
ble_rxValue = "";
ble_rxValue = pCharacteristic->getValue().c_str();
ble_data = pCharacteristic->getData();
pCharacteristic->
if (ble_rxValue.length() > 0) {
for(int i=0;i<ble_rxValue.length();i++)
{
Serial.print(((ble_data++)));
}
ble_get_sta = 1;
}
}
};

[chegewara]

Its not the problem with ble library, just you dont understand what will happen when you do that:
Serial.print(0x0);

[maozhifeng]

这不是 ble 库的问题，只是您不明白这样做时会发生什么：
Serial.print(0x0);

The serial port still can't get the 0x00 I want:
Changed to Serial.write(0x00);

class MyCallbacks: public BLECharacteristicCallbacks { void onWrite(BLECharacteristic *pCharacteristic) { ble_rxValue = ""; ble_rxValue = pCharacteristic->getValue().c_str(); ble_data = pCharacteristic->getData(); if (ble_rxValue.length() > 0) { for(int i=0;i<ble_rxValue.length();i++) { Serial.write((byte)(*(ble_data++))); } } } };

[chegewara]

I am assuming the Serial is output log. What do you expect to see in log by sending empty string?

[maozhifeng]

我假设Serial是输出日志。您希望通过发送空字符串在日志中看到什么？

I can see the return value in the serial debugging tool, so that I can control the esp32 through commands. I need to transmit data through the high and low bits, so it is inevitable to use the 0x00 data

I sent 0x00 through the nrfconnetc software, and didn’t make the callback function work. I don’t know if it’s the phone software problem or esp32 directly filtered out 0x00.

[chegewara]

I can repeat it again and again, there is no problem to send any value with BLE, you can send as many 0x0 as you want. The problem is what you will do with data when you receive it. Maybe try instead of Serial.print another function like Serial.printf("0x%02x", *ble_data);

[maozhifeng]

I can repeat it again and again, there is no problem to send any value with BLE, you can send as many 0x0 as you want. The problem is what you will do with data when you receive it. Maybe try instead of Serial.print another function like Serial.printf("0x%02x", *ble_data);

Thank you for your patience to answer my question, but my current problem is not that esp32 BLE sends data, but that BLE receives data from the mobile app.

For example, the data sent by the mobile app to BLE is: 0x01 0x02 0x00 0x03 0x05;
The getData() function of esp32 BLE can only receive 0x01 0x02, and the data after 0x00 and 0x00 will not be read

[maozhifeng]

我可以一次又一次地重复，用BLE发送任何值都没有问题，您可以发送任意数量的0x0。问题是当你收到数据时你将如何处理它。也许尝试而不是Serial.print另一个功能，如Serial.printf("0x%02x", *ble_data);

感谢您耐心回答我的问题，但我目前的问题不是 esp32 BLE 发送数据，而是 BLE 从移动应用程序接收数据。

比如手机app发送给BLE的数据是：0x01 0x02 0x00 0x03 0x05；
esp32 BLE的getData()函数只能接收0x01 0x02，不会读取0x00和0x00之后的数据

The mobile app is a dedicated Bluetooth debugging software

[chegewara]

my current problem is not that esp32 BLE sends data, but that BLE receives data from the mobile app.

I understand:

class MyCallbacks: public BLECharacteristicCallbacks {
void onWrite(BLECharacteristic pCharacteristic) {
ble_rxValue = "";
ble_rxValue = pCharacteristic->getValue().c_str();
ble_data = pCharacteristic->getData();
pCharacteristic->
if (ble_rxValue.length() > 0) {
for(int i=0;i<ble_rxValue.length();i++)
{
Serial.printf("0x%02x", *(ble_data++));
}
ble_get_sta = 1;
}
}
};

[maozhifeng]

我目前的问题不是 esp32 BLE 发送数据，而是 BLE 从移动应用程序接收数据。

我明白：

class MyCallbacks: public BLECharacteristicCallbacks {
void onWrite(BLECharacteristic pCharacteristic) {
ble_rxValue = "";
ble_rxValue = pCharacteristic->getValue().c_str();
ble_data = pCharacteristic->getData();
pCharacteristic->
if (ble_rxValue.length() > 0) {
for(int i=0;i<ble_rxValue.length();i++)
{
Serial.printf("0x%02x", *(ble_data++));
}
ble_get_sta = 1;
}
}
};

Thank you for your answer. The problem has been solved. The reason is that I used the c_str() function when I tried to convert the std::string type to the String type. This function would return C-style data, thus thinking that 0x00 was the terminator. I cannot receive data after 0x00. Thank you very much for your answer