Kart/serial link

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== Serial link protocol ==
 
== Serial link protocol ==
  
This section defines the serial link protocol used to communicate between the Kart and the BLE module / PC.
+
This section defines the serial link protocol used to communicate between the Kart and the BLE module / PC / Android Smartphone.
  
 
=== General principle ===
 
=== General principle ===
The system using a [[Kart/Bluetooth|BLE]] module, the throughput is limited by design to a payload of 27 bytes each connection interval (from 7.5 ms to 4 s).
+
The system is using a [[Kart/Bluetooth|BLE]] module.
  
 
To avoid congesting the line, data are sent from the Kart to the User on specific '''events''' or if '''requested''' by the User.
 
To avoid congesting the line, data are sent from the Kart to the User on specific '''events''' or if '''requested''' by the User.
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** The FPGA will '''respond to a request''' with the exact same address when W = '0'
 
** The FPGA will '''respond to a request''' with the exact same address when W = '0'
 
** The FPGA will '''save incoming data in the targeted register''' when W = '1'
 
** The FPGA will '''save incoming data in the targeted register''' when W = '1'
** The FPGA will '''send data on predefined events''' with the W bit set to '1'
+
** The FPGA will '''send data on predefined events''' with the W bit set to '0'
 
* RRRRR : targeted register
 
* RRRRR : targeted register
  
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| 0x74
 
| 0x74
 
|}
 
|}
 
 
When the stepper end switch is pressed, imagining that the desired position is reached in the meantime, the FPGA will send the following:
 
{| cellpadding="8" cellspacing="0" border="1"
 
! SoF (1 byte)
 
! Address (1 byte)
 
! Data High (1 byte)
 
! Data Low (1 byte)
 
! EoF (1 byte)
 
|-
 
| 0xAA
 
| 0b01100011
 
| 0b00000000
 
| 0b00000011
 
| 0x47
 
|}
 
 
  
 
If the BLE module wants to read the current battery voltage, supposing we have 4 LEDs, the frame is such as:
 
If the BLE module wants to read the current battery voltage, supposing we have 4 LEDs, the frame is such as:
Line 93: Line 76:
 
| CRC
 
| CRC
 
|}
 
|}
The FPGA will then respond with something like (for a 11.998V reading):
 
{| cellpadding="8" cellspacing="0" border="1"
 
! SoF (1 byte)
 
! Address (1 byte)
 
! Data High (1 byte)
 
! Data Low (1 byte)
 
! EoF (1 byte)
 
|-
 
| 0xAA
 
| 0b10000101
 
| 0x18
 
| 0x09
 
| 0x3D
 
|}
 
 
  
 
== Registers ==
 
== Registers ==
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| Actual steering angle, in motor steps (0 = end switch)
 
| Actual steering angle, in motor steps (0 = end switch)
 
| Kart -> Smartphone
 
| Kart -> Smartphone
| When a delta of at least STP_ANGLE_DELTA_DEG (10°) from the last registered value happens
+
| When a delta of at least STP_ANGLE_DELTA_DEG () from the last registered value happens
 
|-
 
|-
 
| 3
 
| 3
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| Bit 0: stepper end
 
| Bit 0: stepper end
 
Bit 1: position reached
 
Bit 1: position reached
 +
 
Bits 15 - 2 : actual steering angle
 
Bits 15 - 2 : actual steering angle
 
| Kart -> Smartphone
 
| Kart -> Smartphone
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|  
 
|  
 
|-
 
|-
| 3
+
| 7
| LED4
+
| LED8
 
| Bit + Uint15
 
| Bit + Uint15
 
| ''See LED1''
 
| ''See LED1''
Line 222: Line 191:
 
|  
 
|  
 
|-
 
|-
| 4
+
| 8
 
| Voltage
 
| Voltage
 
| Uint16
 
| Uint16
 
| Battery voltage, U = register * 250*e-6 * 7.8 [V]
 
| Battery voltage, U = register * 250*e-6 * 7.8 [V]
 
| Kart -> Smartphone
 
| Kart -> Smartphone
| When a delta of at least SENS_BATT_DELTA_MV (100) from the last registered value happens
+
| When a delta of at least SENS_BATT_DELTA_MV (50) from the last registered value happens
 
|-
 
|-
| 5
+
| 9
 
| Current
 
| Current
 
| Uint16
 
| Uint16
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| When a delta of at least SENS_CURR_DELTA_MA (50) from the last registered value happens
 
| When a delta of at least SENS_CURR_DELTA_MA (50) from the last registered value happens
 
|-
 
|-
| 6
+
| A
 
| Range finder
 
| Range finder
 
| Uint16
 
| Uint16
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Register zeroed if less than 152 mm (sensor min distance) or greater than 1500 mm (arbitrary max distance), event not sent in such case
 
Register zeroed if less than 152 mm (sensor min distance) or greater than 1500 mm (arbitrary max distance), event not sent in such case
 
| Kart -> Smartphone
 
| Kart -> Smartphone
| When a delta of at least SENS_RANGEFNDR_MM (100) from the last registered value happens
+
| When a delta of at least SENS_RANGEFNDR_MM (60) from the last registered value happens
 
|-
 
|-
| 7
+
| B
 
| End switches
 
| End switches
 
| Vector(16)
 
| Vector(16)
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| On any edge change of any sensor
 
| On any edge change of any sensor
 
|-
 
|-
| 8
+
| C
 
| Hall1
 
| Hall1
 
| Uint16
 
| Uint16
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| Each 100 ms if value changed from last time
 
| Each 100 ms if value changed from last time
 
|-
 
|-
| 9
+
| D
 
| Hall2
 
| Hall2
| Uint5 + Uint11
+
| Uint16
 
| ''See Hall1''
 
| ''See Hall1''
 
| Kart -> Smartphone
 
| Kart -> Smartphone
| ''See Hall1''
+
| Each 101 ms if value changed from last time
 
|}
 
|}
  
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Writing range : 0xE0 to 0xFF
 
Writing range : 0xE0 to 0xFF
{{WarningBox|content=
 
The control registers module is '''WRITE ONLY''' for now !
 
}}
 
  
 
{| cellpadding="4" cellspacing="0" border="1"
 
{| cellpadding="4" cellspacing="0" border="1"
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! Description
 
! Description
 
! Direction
 
! Direction
! Event
+
! Comment
 
|-
 
|-
 
| 0
 
| 0
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Bit 4: restart the stepperMotor module, stops the DC motor while '1'
 
Bit 4: restart the stepperMotor module, stops the DC motor while '1'
 
Bit 5: when '1', the BLE connection has been established (otherwise, the Kart should not be able to move)
 
 
| Smartphone -> Kart
 
| Smartphone -> Kart
 
| The end sensor always defines angle 0. Angles are always positive numbers in registers.
 
| The end sensor always defines angle 0. Angles are always positive numbers in registers.
 
If bits 1 and 2 are different, the stepper motor phase sequence has to be inverted.
 
If bits 1 and 2 are different, the stepper motor phase sequence has to be inverted.
 
If the Bluetooth connection is lost, the DC motor has to be stopped.
 
If the Bluetooth connection is lost, the DC motor has to be stopped.
|}
 
 
 
 
 
==== Sequence control register ====
 
 
''The sequence control register is not yet re-implemented.
 
The old behavior, kept for reference, is the following:''
 
 
The sequence control register is used to load a new sequence from start of memory as well as to start and stop a sequence.
 
 
{| cellpadding="4" cellspacing="0" border="1"
 
! Bit
 
! Meaning
 
! Description
 
|-
 
| 0
 
| Reset sequence
 
| sets the sequence RAM write and read addresses back to 0
 
 
|-
 
|-
 
| 1
 
| 1
| Run / stop
+
| BT Status
| starts or stops a sequence
+
| Vector1
|}
+
| Bit 0: when '0', the smartphone is disconnected
 
+
| NRF -> Kart
===== Sequence operations register =====
+
| The register is set by the NRF itself, since it is not possible to foresee the disconnection.
 
+
The sequence memory is made out of 16-bit controls and the sequence can range up to 2<sup>10</sup> operations.
+
From the communication point of view, the sequence memory is seen as a FIFO&nbsp;:
+
the sequence operations are pushed one after the other into the sequence register,
+
starting at the first one of the list after the <code>reset sequence</code> bit
+
has been set in the [[#Control register|control register]]
+
 
+
The sequence operations are split into 2&nbsp;parts: a 4-bit command and optional parameters.
+
A sequence register has been defined in order to build loops:
+
the <code>goto</code> operation is only carried out if the register is not zero.
+
The register is initialised with all bits to&nbsp;'1'.
+
 
+
{| cellpadding="4" cellspacing="0" border="1"
+
|
+
! colspan = "2" | command
+
! parameter
+
| comment
+
|-
+
| Bits
+
! colspan = "2" | 15 ÷ 12
+
! 11 ÷ 0
+
|
+
|-
+
| rowspan = "13" | || 0 || nop || ||
+
|-
+
| 1 || set speed || speed || set the propulsion motor speed
+
|-
+
| 2 || set angle || angle || set the direction motor angle
+
|-
+
| 3 || drive LEDs || pattern || specify a given pattern for turning the LEDs on or off
+
|-
+
| 4 || set LEDs || mask || set bits from '1's of mask
+
|-
+
| 5 || clear LEDs || mask || clear bits from '1's of mask
+
|-
+
| 6 || blink LEDs || period, mask || ''not implemented yet''
+
|-
+
| 8 || run distance || hall ticks || run until the Hall counter has augmented by at least a given tick number
+
|-
+
| 9 || run for || milliseconds || run for a specified time span
+
|-
+
| A || run until || event || ''not implemented yet''
+
|-
+
| D || modify register || operation, operand || bits 11÷10 : 00 = set, 10 = add, 11 = sub / bits 9÷0 : operand
+
|-
+
| E || goto nz || address || jumps to the specified sequence step as long as the register is not zero
+
|-
+
| F || end || || the sequence controller in the FPGA stops and the <code>running</code> status bit is cleared, announcing that the sequence is terminated
+
|}
+
 
+
===== Sequence status register =====
+
 
+
The sequence status register tells what operation is currently active.
+
 
+
{| cellpadding="4" cellspacing="0" border="1"
+
! Bit
+
! Meaning
+
! Description
+
|-
+
| 15 ÷ 12
+
| Current command
+
| indicates which command is currently being processed
+
|-
+
| 0
+
| Running
+
| indicates that a sequence is currently running
+
 
|}
 
|}
  
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* Write '''DC Motor | Prescaler''' to '''31''' (around 21 kHz PWM frequency)
 
* Write '''DC Motor | Prescaler''' to '''31''' (around 21 kHz PWM frequency)
 
* Write '''Stepper Motor | Prescaler''' to '''400''' (250 Hz coil switching frequency)
 
* Write '''Stepper Motor | Prescaler''' to '''400''' (250 Hz coil switching frequency)
* Write '''Control Registers | Hardware Control''' to restart the system while telling the BLE client is connected (0b110xxx)
+
* Tell the smartphone is connected by writing '''Control Registers | BT status''' to 1
 +
* Write '''Control Registers | Hardware Control''' to restart the system (0b10xxx)
 
** The stepper should turn until hitting the end switch, except if already on it
 
** The stepper should turn until hitting the end switch, except if already on it
 
* Read '''Stepper Motor | Stepper HW''' and check the last bit
 
* Read '''Stepper Motor | Stepper HW''' and check the last bit
 
** If is '1', it means we are already zeroed
 
** If is '1', it means we are already zeroed
 
** If not, wait for an event from this register to tell the reset is complete
 
** If not, wait for an event from this register to tell the reset is complete
* Write '''Control Registers | Hardware Control''' to deassert the reset (0b100xxx)
+
* Write '''Control Registers | Hardware Control''' to deassert the reset (0b00xxx)
  
 
The Kart is now ready to function !
 
The Kart is now ready to function !
 +
 +
Note that the '''Control Registers | restart''' bit is automatically reset back to 0 when the
 +
''stepper_end'' input is activated.
  
 
== Testing through USB ==
 
== Testing through USB ==
 
[[File:Kart_kci.jpg|450px|right|Kart Command Interpreter]]
 
[[File:Kart_kci.jpg|450px|right|Kart Command Interpreter]]
 
To test the Kart from a PC directly, one can do as follows:
 
To test the Kart from a PC directly, one can do as follows:
* Remove the [[Kart/Bluetooth|BLE]] from the [[Kart/Motherboard|motherboard]]
+
* Remove the [[Kart/Bluetooth|BLE]] from the [[Kart/Motherboard|motherboard]] (or, at least, do not connect to a smartphone)
 
* Power the [[Kart/Motherboard|motherboard]] with a DC voltage regulator (+12V)
 
* Power the [[Kart/Motherboard|motherboard]] with a DC voltage regulator (+12V)
 
* Wire the USB-C present on the daughterboard to your PC
 
* Wire the USB-C present on the daughterboard to your PC
Line 418: Line 300:
 
* Download and open the '''Kart Command Interpreter''' utility (available in the VHDL project -> CommandInterpreter)
 
* Download and open the '''Kart Command Interpreter''' utility (available in the VHDL project -> CommandInterpreter)
 
** [https://github.com/hei-synd-2131-eln/eln-kart/blob/master/CommandInterpreter/KartCommandInterpreter_WIN.exe Windows 10]
 
** [https://github.com/hei-synd-2131-eln/eln-kart/blob/master/CommandInterpreter/KartCommandInterpreter_WIN.exe Windows 10]
** [https://github.com/hei-synd-2131-eln/eln-kart/blob/master/CommandInterpreter/KartCommandInterpreter_MAC Mac]
 
 
** [https://github.com/hei-synd-2131-eln/eln-kart/blob/master/CommandInterpreter/KartCommandInterpreter_LIN Linux]
 
** [https://github.com/hei-synd-2131-eln/eln-kart/blob/master/CommandInterpreter/KartCommandInterpreter_LIN Linux]
 +
** [https://github.com/hei-synd-2131-eln/eln-kart/blob/master/CommandInterpreter/commandInterpreter.py Source code]
 
* In the top menu '''Serial -> Port''', select the correct COM port (should be the biggest of the two new ports)
 
* In the top menu '''Serial -> Port''', select the correct COM port (should be the biggest of the two new ports)
** You can also change the baudrate, by default '''115'200''' (the correct one if it was not modified in the VHDL '''Kart_pkg.vhd'''
+
** You can also change the baudrate, by default '''115'200''' (the correct one if it was not modified)
  
 
To test the connection, click the '''Read''' button. The '''Tx''' and '''Rx''' values should change, and a text added to the text area.
 
To test the connection, click the '''Read''' button. The '''Tx''' and '''Rx''' values should change, and a text added to the text area.
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* '''Init Kart''' button
 
* '''Init Kart''' button
 
** Will set the DC prescaler, stepper prescaler, and execute the restart sequence. '''Must be clicked first.'''
 
** Will set the DC prescaler, stepper prescaler, and execute the restart sequence. '''Must be clicked first.'''
** You may need to modifiy the [[Kart/serial_link#Control_Registers|'''CReg -> HW Control''']] register to correspond to your Kart design. Only change x in the following value: '''0b100xxx'''
+
** Answer the 4 prompts following your hardware configuration.
 
* '''DC Motor''' button
 
* '''DC Motor''' button
 
** Will set the DC speed to full for 2s, quickly 0, then reversed full speed for 2s
 
** Will set the DC speed to full for 2s, quickly 0, then reversed full speed for 2s

Revision as of 12:15, 6 September 2022

Contents

Serial link protocol

This section defines the serial link protocol used to communicate between the Kart and the BLE module / PC / Android Smartphone.

General principle

The system is using a BLE module.

To avoid congesting the line, data are sent from the Kart to the User on specific events or if requested by the User.

Serial port

Communication is done with:

  • Resting state : HIGH
  • Data bits : 8
  • Parity : none
  • Stop bits : 1
  • Handshake : none
  • Baudrate : 115'200

Message Format

SoF (1 byte) Address (1 byte) Data (2 bytes) EoF (1 byte)
0xAA UINT8 UINT16/INT16/VECTOR16 (MSB first) CRC8/ITU

The address is decomposed as follows: 0bMMWRRRRR

  • MM : targeted module
    • 0b00 : DC Motor
    • 0b01 : Stepper Motor
    • 0b10 : Sensors
    • 0b11 : Control Registers
  • W : defines if the data is saved to ('1') or read from ('0') the FPGA
    • The FPGA will respond to a request with the exact same address when W = '0'
    • The FPGA will save incoming data in the targeted register when W = '1'
    • The FPGA will send data on predefined events with the W bit set to '0'
  • RRRRR : targeted register

Frame example

For the BLE module to light LED1 with it changing each 500 ms, the following frame is sent:

SoF (1 byte) Address (1 byte) Data High (1 byte) Data Low (1 byte) EoF (1 byte)
0xAA 0b10100001 0b10000001 0b11110100 0x74

If the BLE module wants to read the current battery voltage, supposing we have 4 LEDs, the frame is such as:

SoF (1 byte) Address (1 byte) Data High (1 byte) Data Low (1 byte) EoF (1 byte)
0xAA 0b10000101 Any Any CRC

Registers

DC Motor

Reading range : 0x00 to 0x1F

Writing range : 0x20 to 0x3F

Address Name Type Description Direction Event
0 Prescaler Uint16 DC PWM frequency, as fclk / (PWMsteps * prescaler) = 10M / (16 * prescaler) Smartphone -> Kart
1 Speed Int5 Desired speed, from -15 (0xFFF1) to 15 (0x000F) (negative = backward) Smartphone -> Kart


Stepper Motor

Reading range : 0x40 to 0x5F

Writing range : 0x60 to 0x7F

Address Name Type Description Direction Event
0 Prescaler Uint16 Stepper switching frequency, as 100k / prescaler Smartphone -> Kart
1 Target angle Uint16 Desired steering angle, in motor steps (0 = end switch) Smartphone -> Kart
2 Actual angle Uint16 Actual steering angle, in motor steps (0 = end switch) Kart -> Smartphone When a delta of at least STP_ANGLE_DELTA_DEG (3°) from the last registered value happens
3 Stepper HW Uint14 + Vector2 Bit 0: stepper end

Bit 1: position reached

Bits 15 - 2 : actual steering angle

Kart -> Smartphone Sent when stepper end is pressed (rising edge) or position reached (rising edge)

Sensors

Reading range : 0x80 to 0x9F

Writing range : 0xA0 to 0xBF

Address Name Type Description Direction Event
0 LED1 Bit + Uint15 Bit 15: on / off/

Bits 14 -> 0: half-period in ms (if 0, led status = bit 15)

Smartphone -> Kart
...
7 LED8 Bit + Uint15 See LED1 Smartphone -> Kart
8 Voltage Uint16 Battery voltage, U = register * 250*e-6 * 7.8 [V] Kart -> Smartphone When a delta of at least SENS_BATT_DELTA_MV (50) from the last registered value happens
9 Current Uint16 Consumed current, I = register * 250*10*e-6 / (100 * 5*10*e-3) [A] Kart -> Smartphone When a delta of at least SENS_CURR_DELTA_MA (50) from the last registered value happens
A Range finder Uint16 Distance to sensor, register * 25.4 / (147*10*e-6 * (10M / 10)) [mm]

Register zeroed if less than 152 mm (sensor min distance) or greater than 1500 mm (arbitrary max distance), event not sent in such case

Kart -> Smartphone When a delta of at least SENS_RANGEFNDR_MM (60) from the last registered value happens
B End switches Vector(16) Sensors current values, right justified (sensor 1 is bit 0) Kart -> Smartphone On any edge change of any sensor
C Hall1 Uint16 Hall pulses count, zeroed on overflow of the register Kart -> Smartphone Each 100 ms if value changed from last time
D Hall2 Uint16 See Hall1 Kart -> Smartphone Each 101 ms if value changed from last time

Control Registers

Reading range : 0xC0 to 0xDF

Writing range : 0xE0 to 0xFF

Address Name Type Description Direction Comment
0 Hardware Control Vector6 Bit 0: when '0', the Kart goes backwards when the motor turns foward

Bit 1: when '1', the Kart turns to the right as the stepper coils go from 1 to 4

Bit 2: when '1', the angles are measured clockwise

Bit 3: emulates the end switch contact for the stepper motor

Bit 4: restart the stepperMotor module, stops the DC motor while '1'

Smartphone -> Kart The end sensor always defines angle 0. Angles are always positive numbers in registers.

If bits 1 and 2 are different, the stepper motor phase sequence has to be inverted. If the Bluetooth connection is lost, the DC motor has to be stopped.

1 BT Status Vector1 Bit 0: when '0', the smartphone is disconnected NRF -> Kart The register is set by the NRF itself, since it is not possible to foresee the disconnection.

Kart init

To init the Kart, the following sequence should be sent to the Kart:

  • Write DC Motor | Prescaler to 31 (around 21 kHz PWM frequency)
  • Write Stepper Motor | Prescaler to 400 (250 Hz coil switching frequency)
  • Tell the smartphone is connected by writing Control Registers | BT status to 1
  • Write Control Registers | Hardware Control to restart the system (0b10xxx)
    • The stepper should turn until hitting the end switch, except if already on it
  • Read Stepper Motor | Stepper HW and check the last bit
    • If is '1', it means we are already zeroed
    • If not, wait for an event from this register to tell the reset is complete
  • Write Control Registers | Hardware Control to deassert the reset (0b00xxx)

The Kart is now ready to function !

Note that the Control Registers | restart bit is automatically reset back to 0 when the stepper_end input is activated.

Testing through USB

Kart Command Interpreter

To test the Kart from a PC directly, one can do as follows:

  • Remove the BLE from the motherboard (or, at least, do not connect to a smartphone)
  • Power the motherboard with a DC voltage regulator (+12V)
  • Wire the USB-C present on the daughterboard to your PC
    • Two new COM ports should be detected
  • Download and open the Kart Command Interpreter utility (available in the VHDL project -> CommandInterpreter)
  • In the top menu Serial -> Port, select the correct COM port (should be the biggest of the two new ports)
    • You can also change the baudrate, by default 115'200 (the correct one if it was not modified)

To test the connection, click the Read button. The Tx and Rx values should change, and a text added to the text area.

Simple operation

The simplest way to test both motors are the three button at the bottom.

  • Init Kart button
    • Will set the DC prescaler, stepper prescaler, and execute the restart sequence. Must be clicked first.
    • Answer the 4 prompts following your hardware configuration.
  • DC Motor button
    • Will set the DC speed to full for 2s, quickly 0, then reversed full speed for 2s
  • Stepper Motor button
    • Will set the stepper to 400 (30°) then 0

Custom operation

Each register can be read and/or written by hand following their data description.

For this, select the Module first, then which Register.

Read

To read, simply click the Read button. Successful read will be shown in green (CRC is ok) and logged, with extra info (e.g. for the DC prescaler, will give the motor frequency).

Write

To write, enter a value in the value box such as:

  • Direct integer (only DC speed should be negative)
  • 0bxxxx binary values
  • 0xxxxx hexadecimal values
  • Other values will throw an error

Then click on the Write button.

Reset

In case of problem, you can simply power-cycle the FPGA board to reset the registers.

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