select();
  SPI.transfer(REG_FIFO | 0x80); // Select the FIFO write register.

  SPI.transfer(bufferSize + 5); // rfm69_header_t.packetLen
  SPI.transfer(toAddress); // rfm69_header_t.recipient
  SPI.transfer(1); // RFM69_PACKET_HEADER_VERSION = (1u) rfm69_header_t.version header version (20180128tk: >=3.0.0 fused with controlFlags)
  SPI.transfer(_address); // rfm69_header_t.sender
  SPI.transfer(CTLbyte); // rfm69_header_t.controlFlags
  SPI.transfer(0); // rfm69_header_t.sequenceNumber

  for (uint8_t i = 0; i < bufferSize; i++)
    SPI.transfer(((uint8_t*) buffer)[i]);
  unselect();

So after adding SPI.transfer(1); as rfm69_header_t.version and SPI.transfer(0); as rfm69_header_t.sequenceNumber the packets are now being parsed correctly:

DEBUG TSF:MSG:READ,1-1-255,s=3,c=1,t=16,pt=1,l=1,sg=0:1
DEBUG TSF:MSG:BC

I've created an ATTiny841 node with the RFM69CW radio (with a modified RFM69 library to match the radio config registers of MySensors) but the Raspberry Pi gateway is seeing the packets different.

Here is the sending part:

byte test[] = {
  1, // last
  1, // sender
  255, // destination
  0b00001010, // version_length: 2 bit - Protocol version (2), 1 bit - Signed flag (no), 5 bit - Length of payload (1 byte)
  0b00100001, // command_ack_payload: 3 bit - Command type (C_SET), 1 bit - Request an ack (no), 1 bit - Is ack message (no), 3 bit - Payload data type (P_BYTE)
  16, // type: V_TRIPPED
  3, // sensor ID
  1 // Value: 1
};

radio.send(255, packet, strlen(packet));

which is received as:

DEBUG TSF:MSG:READ,10-255-33,s=0,c=3,t=1,pt=0,l=2,sg=0:
DEBUG !TSF:MSG:LEN,6!=9

where none of the fields match the packet :(

Here is the packet definition in core/MyMessage.h:

uint8_t last;            	 ///< 8 bit - Id of last node this message passed
uint8_t sender;          	 ///< 8 bit - Id of sender node (origin)
uint8_t destination;     	 ///< 8 bit - Id of destination node

/**
 * 2 bit - Protocol version<br>
 * 1 bit - Signed flag<br>
 * 5 bit - Length of payload
 */
uint8_t version_length;

/**
 * 3 bit - Command type<br>
 * 1 bit - Request an ack - Indicator that receiver should send an ack back<br>
 * 1 bit - Is ack message - Indicator that this is the actual ack message<br>
 * 3 bit - Payload data type
 */
uint8_t command_ack_payload;

uint8_t type; ///< 8 bit - Type varies depending on command
uint8_t sensor; ///< 8 bit - Id of sensor that this message concerns.

/*
 * Each message can transfer a payload. We add one extra byte for string
 * terminator \0 to be "printable" this is not transferred OTA
 * This union is used to simplify the construction of the binary data types transferred.
 */
union {
    uint8_t bValue; ///< unsigned byte value (8-bit)
    uint16_t uiValue; ///< unsigned integer value (16-bit)
    int16_t iValue; ///< signed integer value (16-bit)
    uint32_t ulValue; ///< unsigned long value (32-bit)
    int32_t lValue; ///< signed long value (32-bit)
    struct { //< Float messages
        float fValue;
        uint8_t fPrecision; ///< Number of decimals when serializing
    };
    struct {  //< Presentation messages
        uint8_t version; ///< Library version
        uint8_t sensorType; ///< Sensor type hint for controller, see table above
    };
    char data[MAX_PAYLOAD + 1]; ///< Buffer for raw payload data
} __attribute__((packed)); ///< Doxygen will complain without this comment

I'll try and log the raw incoming packet on the Pi side just to confirm that the radio config is actually matching.

For now I got Humidity and Voltage(VCC) running up fine.

0;255;3;0;9;TSM:READY:NWD REQ<\n>
0;255;3;0;9;TSF:MSG:SEND,0-0-255-255,s=255,c=3,t=20,pt=0,l=0,sg=0,ft=0,st=OK:<\n>
Fatal exception 28(LoadProhibitedCause):<\n>
epc1=0x40202704, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000003, depc=0x00000000<\n>
<\r><\n>

In my handcrafted packet I use this as the 4thy byte send:

0b10000001

So to craft this I looked at MyMessage.h which showed me this:

uint8_t version_length;		 // 2 bit - Protocol version
		                 // 1 bit - Signed flag
		                 // 5 bit - Length of payload

So from my understanding:

Protocol Version = 2 => 0b10
Signed Flag = 0 => 0b0
Length of Payload = 1 = 0b00001

Which results in 0b10 0 00001 = 0b10000001

But I get this error:

LEN,8!=23

So .. where might this come from?

radio.write(test,8);

Mycontroller received a packet with the length of 8 but expected a packet with the length of .. 23 ?!

#define mGetLength(_message) ((uint8_t)BF_GET(_message.version_length, 3, 5)) //!< Get length field

Which in essential is BF_GET ..

#define BF_GET(y, start, len)   ( ((y)>>(start)) & BIT_MASK(len) ) //!< Extract a bitfield of length 'len' starting at bit 'start' from 'y'

So what is happening?

BF_GET(0b10000001, 3, 5)   ( ((0b10000001)>>(3)) & BIT_MASK(5) ) //!< Extract a bitfield of length 'len' starting at bit 'start' 

Whoops? This will throw away all the length-information!!!
(0b10000001)>>(3)
This should result in:
0b11110000 & BIT_MASK5 = 0b1111000 & 0b00011111 = 0b00010000 = 16 decimal

const uint8_t expectedMessageLength = HEADER_SIZE + (mGetSigned(_msg) ? MAX_PAYLOAD : msgLength);

const uint8_t expectedMessageLength = 7+ 16); // = 23

Yeah .. the lib is right .. 8 != 23 .. but the handcrafted length = 1 + header_length (7) = 8

Am I wrong or is this a bug?

Edit: I might have read the comments in the source code the wrong way

MyGateway: ESP8266 + mysensorsMQTT
MyNode: https://github.com/Miceuz/PlantWateringAlarm
MyNode-MCU: Attiny44 (MemoryFootprint: 87% of 4KB)
ArduinoCore: https://github.com/SpenceKonde/ATTinyCore
ArduinoCore-PinLayout: Counterclockwise (like AttinyCore)
Note: The default "counterclockwise"pinout is the alternate pinout shown here: https://github.com/SpenceKonde/ATTinyCore/blob/master/avr/extras/ATtiny_x4.md

The important hint is here (http://tmrh20.github.io/RF24/ATTiny.html)

Connect MOSI of the RF24 to PA5 of the attiny and MISO of the RF24 to PA6 of the attiny.
CE = 8
CSN = 7

To get the connection done right DONT .. i mean DO NOT BECAUSE IT DOESNT FUCKING WORK connect MOSI of the RF24 to MOSI of the attiny. RF24 uses a embedded implementation of the USI-engine found on some AtTiny's.

radio-initilisation

    radio.begin(); // Start up the radio
    radio.setDataRate(RF24_250KBPS);
    radio.setAutoAck(1); // Ensure autoACK is enabled
    radio.setRetries(15,15); // Max delay between retries & number of retries
    //radio.setPayloadSize(8);
    radio.enableDynamicPayloads();
    radio.setPALevel(RF24_PA_MAX);
    byte tx_address[] = { 0x00, 0xFC, 0xE1, 0xA8, 0xA8 };
    //byte tx_address[] = { 0xA8, 0xA8, 0xE1, 0xFC, 0x00 };
    radio.openWritingPipe(tx_address);
    radio.stopListening();

Send-Function:

void sendHumidity(uint16_t humidity)
{
    // snprintf_P(_fmtBuffer, MY_GATEWAY_MAX_SEND_LENGTH, PSTR("%s/%d/%d/%d/%d/%d"), prefix, message.sender, message.sensor, mGetCommand(message), mGetAck(message), message.type);
    // X8X22<\0><\n>!<7>7AY0;255;3;0;9;TSF:MSG:READ,50-50-0,s=55,c=1,t=7,pt=1,l=1,sg=0:65<\n>
    // 0;255;3;0;9;Sending message on topic: domoticz/in/MyMQTT/50/55/1/0/7<\n>
    
    #define LAST_NODE_ID  50  // last
    #define NODE_ID       50  // sender
    #define GATEWAY_ID    0   // destination
    
                              // version_length     // 5 bit - Length of payload // 1 bit - Signed flag // 2 bit - Protocol version
                              // command_ack_payload // 3 bit - Payload data type // 1 bit - Is ack messsage - Indicator that this is the actual ack message. // 1 bit - Request an ack - Indicator that receiver should send an ack back. // 3 bit - Command type
    
    #define SENSOR_TYPE   7   // type S_HUM = 7
    #define SENSOR_ID     55  // sensor-id
    byte test[] = { LAST_NODE_ID, NODE_ID, GATEWAY_ID, 0b00010010, 0b01100001,  SENSOR_TYPE, SENSOR_ID, (uint8_t)(humidity & 0x00FF), (uint8_t)((humidity >> 8) & 0x00FF),  0x00 };
    radio.write(test,9);
}

I am not quite sure yet if the message-types etc. are right but I am trying to find this out. 'A' (dec 65) is the "value" of my humidity .. next step is to make this a real value ofc.

Proof at domoticz:

@gohan: In the file MyConfig.h I commented this out:

/**
 * @def MY_REGISTRATION_FEATURE
 * @brief If enabled, node has to register to gateway/controller before allowed to send sensor data.
 */
// #define MY_REGISTRATION_FEATURE

This will skip the whole hasse of registering the client properly (which I can't .. remember 87% of flash is full)