uint8 array passing value fail - only one uint8_t sent - c++

Question

I try to start a array in the header file
rs485.h
class RS485
{
public:
uint8_t off[] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07};
void sendmsg(uint8_t* cmd);
};
rs485.cpp
void RS485::sendmsg(uint8_t* cmd)
{
//digitalWrite(ENTX_PIN, HIGH); // enable to transmit
Serial.println("sending message------------");
Serial2.write(cmd[0]);
Serial.println(cmd[0], HEX);
Serial2.write(cmd[1]);
Serial.println(cmd[1], HEX);
Serial2.write(cmd[2]);
Serial.println(cmd[2], HEX);
Serial2.write(cmd[3]);
Serial.println(cmd[3], HEX);
Serial2.write(cmd[4]);
Serial.println(cmd[4], HEX);
Serial2.write(cmd[5]);
Serial.println(cmd[5], HEX);
Serial2.write(cmd[6]);
Serial.println(cmd[6], HEX);
Serial2.write(cmd[7]);
Serial.println(cmd[7], HEX);
Serial.println("--------------------------");
}
main.cpp
void callback(char *topic, byte *payload, unsigned int length)
{
'''omit'''
if (cmd)
{
Serial.print("cmd: ");
Serial.println(cmd);
if (cmd == 700)
{
rs485.sendmsg(rs485.off);
}
else if (cmd == 701)
{
rs485.sendmsg(rs485.on);
}
'''omit'''
}
'''omit'''
}
complier have an error message of "too many initializer values".
When I try to use
uint8_t off[8] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07};
it build normally. The problem is when in use this variable in main.cpp and pass it to rs485.cpp only one element off[0] is pass normally.
rs485.sendmsg(rs485.off);
I have use serial print to check all value it can all print out but the rs485 cannot tx all char.
Serial2.write(cmd[0]);
Serial.println(cmd[0], HEX);
Serial2.write(cmd[1]);
Serial.println(cmd[1], HEX);
Serial2.write(cmd[2]);
Serial.println(cmd[2], HEX);
Serial2.write(cmd[3]);
Serial.println(cmd[3], HEX);
Serial2.write(cmd[4]);
Serial.println(cmd[4], HEX);
Serial2.write(cmd[5]);
Serial.println(cmd[5], HEX);
Serial2.write(cmd[6]);
Serial.println(cmd[6], HEX);
Serial2.write(cmd[7]);
Serial.println(cmd[7], HEX);
Any result for that?
add the wiring
gpio26 -->DE+RE
gpio21 -->DI
gpio25 -->RO

Answer 1

A member variable declared as
uint8_t off[] = { ... };
does not become an array with the number of elements in the initializer list, like when you declare a non-member variable. Instead, it then becomes a "flexible array" (a C thing that g++ enables by default in C++) - and flexible arrays can't have initializers, which is why you get "too many initializer values".
The correct way is therefore to specify the number of elements:
uint8_t off[8] = { ... };
I suggest that you send them all out at once and check how many that are actully written:
size_t written = Serial2.write(cmd, 8);
Serial.println(written);
This should display 8 if the sending code works.