Communication with OBC

The UART_3 serial port is used to implement payload communication with OBC. The logic and structure of the communication frame are described below.

Communication frame structure

Communication between the payload and OBC is based on two types of frames: read/write frame and ACK/NACK frame. Read/write frame is used to send or request data. ACK/NACK informs about successful or unsuccessful transaction. There is also one special type of frame - log frame.

Read/write frame

#	Description	Size	Value
1	preambule	5b	0b11010
2	data size	2b
3	read/write flag	1b	0b1-read 0b0-write
4	register address	8b
5	data word 1	16b
6	data word 2	16b
7	data word 3	16b
8	CRC	16b

Data: 16b data words are sent split into 2 bytes in the following order: 1. Least significant byte 2. Most significant byte. CRC: 16b CRC word is sent split in the same way as data words. CRC is calculated from the first 8 bytes, which includes swapped bytes of data words.

ACK/NACK frame

#	Description	Size	Value
1	preambule	5b	0b10101
2	data size	2b	00
3	correct/incorrect	1b	0b1-ok 0b0-not
4	register address	8b

Log frame

#	Description	Size	Value
1	preambule	5b	0b11010
2	data size	2b	0b11
3	read/write flag	1b	0b0
4	log type	8b	0x82-normal log / 0xF8-special log
5	timestamp	16b	​
6	data id	16b	​
7	data value	16b	​
8	CRC	16b

Communication commands logic

Communication - write flowchart

Communication - read flowchart

Payload commands

Name	Add	Description	Size	Values
REG_ADD_SR_ADCS_COIL_X	66 67	Set PWM of coil X to a given value.	int16	-100 to 100
REG_ADD_SR_ADCS_COIL_Y	68 69	Set PWM of coil Y to a given value.	int16	-100 to 100
REG_ADD_SR_ADCS_PWM	208 209	Confirm setting PWM of coils X and Y to given values.	X: int8 Y: int8	-100 to 100 -100 to 100
REG_ADD_SR_ADCS_STATUS	206	lnform payload OBC about status of SatRevolution detumbling process.	uint16	0 - unknown /in progress 1 - success 2 - error
REG_ADD_ADCS_COIL X_VALUE	160 161	Set in manual mode PWM of coil X to a given value.	int16	-100 to 100
REG_ADD_ADCS_COIL Y_VALUE	162 163	Set in manual mode PWM of coil Y to a given value.	int16	-100 to 100
REG_ADD_ADCS_COIL Z_VALUE	164 165	Set in manual mode PWM of coil Z to a given value.	int16	-100 to 100
REG_ADD_MODE_TIME	180 181	Set the current mode’s timer_1s value to a given value multiplied by the current mode’s timer_prescaler.	uint16	0 - default ($2^{16}$ - 1) - infinity
REG_ADD_MODE	178	Set mode with id equal to the given value as the current mode	uint8	0 to 8
REG_ADD_MODE_NEXT	179	Set mode with id equal to the given value as the next mode after current.	uint8	0 to 9 9 - current as next
REG_ADD_LOG1MIN_ CONFIG_ADD_REG	184 185	Add register of given value to the log list in 1min period log mode.	uint16	136 to 255
REG_ADD_LOG1S_ CONFIG_ADD_REG	188 189	Add register of given value to the log list in 1s period log mode.	uint16	136 to 255
REG_ADD_LOG200MS_ CONFIG_ADD_REG	192 193	Add register of given value to the log list in 200ms period log mode.	uint16	136 to 255
REG_ADD_LOG1MIN_ CONFIG_DLT_REG	186 197	Delete register of given value from the log list in 1min period log mode.	uint16	136 to 255 1 - clear list
REG_ADD_LOG1S_ CONFIG_DLT_REG	190 191	Delete register of given value from the log list in 1s period log mode.	uint16	136 to 255 1 - clear list
REG_ADD_LOG200MS_ CONFIG_DLT_REG	194 195	Delete register of given value from the log list in 200ms period log mode.	uint16	136 to 255 1 - clear list
REG_ADD_STOP_LOGS	246 247	Stop or start logging data.	uint16	0 - START 1 - STOP
REG_ADD_SPECIAL_ LOG_BUFF	254 255	Inform whether the special log buffer is full. If so - log to normal buffer.	uint16	0 - FULL 1 - NOT FULL

Setting calibration parameters

To set any of constant parameters in the equations mentioned above, there is a need to define the address and value of the designated coefficient. This is done by writing the following registers:

• REG_ADD_FLASH_CONFIG_PARAM_<ID> - ID of the parameter from the table below

• REG_ADD_FLASH_CONFIG_VALUE_<1 or 2> - float value of the parameter

Param ID	Description
0	Gyro matrix $A_t$ component $A_{t_{1,1}}$
1	Gyro matrix $A_t$ component $A_{t_{2,2}}$
2	Gyro matrix $A_t$ component $A_{_{t3,3}}$
3	Gyro vector$b_t$ component $b_{t_1}$
4	Gyro vector$b_t$ component $b_{t_2}$
5	Gyro vector$b_t$ component $b_{t_3}$
6	Gyro matrix $A$ component $A_{1,1}$
7	Gyro matrix $A$ component $A_{2,1}$
8	Gyro matrix $A$ component $A_{3,1}$
9	Gyro matrix $A$ component $A_{1,2}$
10	Gyro matrix $A$ component $A_{2,2}$
11	Gyro matrix $A$ component $A_{3,2}$
12	Gyro matrix $A$ component $A_{1,3}$
13	Gyro matrix $A$ component $A_{2,3}$
14	Gyro matrix $A$ component $A_{3,3}$
15	Gyro vector$o$ component $o_1$
16	Gyro vector$o$ component $o_2$
17	Gyro vector$o$ component $o_3$
18	Mag matrix $A_t$ component $A_{t_{1,1}}$
19	Mag matrix $A_t$ component $A_{t_{2,2}}$
20	Mag matrix $A_t$ component $A_{t_{3,3}}$
21	Mag vector $b_t$ component $b_{t_1}$
22	Mag vector $b_t$ component $b_{t_2}$
23	Mag vector $b_t$ component $b_{t_3}$
24	Mag matrix $A$ component $A_{1,1}$
25	Mag matrix $A$ component $A_{2,1}$
26	Mag matrix $A$ component $A_{3,1}$
27	Mag matrix $A$ component $A_{1,2}$
28	Mag matrix $A$ component $A_{2,2}$
29	Mag matrix $A$ component $A_{3,2}$
30	Mag matrix $A$ component $A_{1,3}$
31	Mag matrix $A$ component $A_{2,3}$
32	Mag matrix $A$ component $A_{3,3}$
33	Mag vector $o$ component $o_1$
34	Mag vector $o$ component $o_2$
35	Mag vector $o$ component $o_3$
36	Temperature regression coefficient (IMU) $t_k$
37	Temperature regression coefficient (IMU) $t_o$
38	Temperature regression coefficient ($\mu C$) $t_a$
39	Temperature regression coefficient ($\mu C$) $t_b$
40	Temperature regression coefficient (FRW) $t_a$
41	Temperature regression coefficient (FRW) $t_b$

Logging logic

By default, payload logs data by sending log frames with log type 0x82 (normal log). There is also a second log type 0xF8 (special log) used in modes: Diagnostic, Detumbling and F.R.W. experiment. Special logs are high value data and are stored in non-shift buffer. The attached sheet describes the logged data and its frequency in every mode.

71KB

KRAKsat payload logs.pdf

pdf

KRAKsat OBC has implemented logic, which supports the storage of various types of logs. Logs are stored in different memory spaces depending on their type and memory space availability.

Logging logic flowchart