Attiny protocol
Cette section à été rédigée en anglais et ne sera volontairement pas traduite. En tant que roboticiens vous aurez à lire des datasheet en anglais uniquement. Ce n'est vraiment pas évident au début, alors ça vous servira d'entrainement ; )
The Attiny1616 featured in the tuto board controls 9 leds, and has 2 inputs : a potentiometer and a phototransistor, acting as light sensor.
The protocol documented here allows you to interact with the Attiny.
Packets sent by the nucleo to the Attiny will be called Tx packets. Those sent by the Attiny to the nucleo will be called Rx packets.
Message format All messages have the same format :
| STX | LEN | PAYLOAD[...] | CHK |
|---|
STX Start of the packet. STX=0xFF.
LEN Byte size of the PAYLOAD and CHK field.
PAYLOAD See Tx packets and Rx Packets.
CHK Checksum for the packet. CHK = ~(LEN + PAYLOAD[0] + … + PAYLOAD[N])
Tx packets
Payload of Tx packets is made of a 1 byte instruction optionally followed by parameters.
| STX | LEN | INSTRUCTION | PARAM 1 | ... | PARAM N | CHK |
|---|
The instructions are:
PING
- Value: 0x01
- Parameters: None
- Description: Ping the Attiny.
- Answer: PONG message.
READ
- Value: 0x02
- Parameters: Address (1byte), count (1byte)
- Description: Request the values of the <count> registers, starting at <address>. Answer: REG message.
WRITE
- Value: 0x03
- Parameters: address, value1, value2, …
- Description: Write the <values> at registers starting at <address>. The register address is auto-incremented.
- Answer: None
Rx packets
Payload of Rx packets is made of a 1 byte identifier optionally followed by data.
PONG
- Value: 0x11
- Data: no data
REG
- Value: 0x12
- Data: values
CONTINUOUS
- Value: 0x13
- Data: 2 bytes defined as follow:
| data_id[1:0] | RESERVED | data[9:8] | data[7:0] |
|---|
Where data_id identify the nature of the data:
0x0: potentiometer value
0x1: light value
0x2: leds status
The data itself spans over 10 bits for potentiometer and light values, and 9 bits for leds status.
Registers description
| Name | Address | Rights |
|---|---|---|
| POT_L | 0X00 | R |
| POT_H | 0X01 | R |
| LIGHT_L | 0X02 | R |
| LIGHT_H | 0X03 | R |
| LEDS_L | 0X04 | RW |
| LEDS_H | 0X05 | RW |
| MODE | 0X06 | RW |
POT
Description: 10 bits potentiometer value.
| RESERVED | POT[9:8] |
|---|
| POT[7:0] |
|---|
LIGHT
Description: 10 bits light value.
| RESERVED | LIGHT[9:8] |
|---|
| LIGHT[7:0] |
|---|
LEDS
Description: State of the leds. 0 is OFF, 1 is ON.
| RESERVED | LEDS[8] |
|---|
| LEDS[7:0] |
|---|
LEDS default value: 0
MODE
Description:
- POTC: if set, the Attiny will send CONTINUOUS potentiometer data.
- LIGHTC: if set, the Attiny will send CONTINUOUS light data.
- LEDSC: if set, the Attiny will send CONTINUOUS leds data.
- CFREQ: frequency at which CONTINUOUS messages will be sent.
| POTC | LIGHTC | LEDSC | CFREQ[1:0] | LEDSMODE[2:0] |
|---|---|---|---|---|
| 0x0: 50ms (20Hz) | 0x0: MANUAL | |||
| 0x1: Pot value | 0x1: 100ms (10Hz) | |||
| 0x2: Light value | 0x2: 200ms (5Hz) | |||
| 0x3: Pot speed | 0x3: 500ms (2Hz) | |||
| 0x4: Light speed |
Default values:
- POTC: 0
- LIGHTC: 0
- LEDSC: 0
- CFREQ: 0X01
- LEDSMODE: 0x1 (Pot value)