Some time ago (about a year?) I started a project, kap-rx2 that I wanted to grow into a new KAP receiver. It didn’t get far before it went dormant but lately I’ve been putting it back on the front burner. At the moment, it runs FreeRTOS and an event manager with some degree of buffer management. It has a CLI that runs over a UART (USART2) and there’s an ESP8266 connected on USART6.
About the only thing the code actually does right now is act as a terminal between the console and the ESP8266. So one can manually type AT commands and see how the ESP8266 responds.
Since I want to resume work on this, I feel I need to review the software pieces already in place.
Software Architecture
The basic software architecture is based on FreeRTOS, which provides threading, and an event processor, which provides lightweight event-driven capabilities.
The application is written, primarily in C++.
main
Main (as well as the project file) were generated by STM32CubeMX.
A lot of MX subsystems get initialized.
serial_init() is called to initialize the two serial interfaces.
defaultTask is created. This task, in main.c, initializes FATFS, prints the “kap-rx2 controller” message, starts hardware PWM, then runs CLI.
evtMgrInit() is called to create event manager task.
Tasks
defaultTask, in main.c, runs the CLI loop after system initialization. etMgrTask, in EvtMgr.cpp, runs the event manager thread.
Event Manager
The event manager is implemented as a FreeRTOS task. So all events are dispatched in the context of this one thread.
EvtMgr class:
- issueEvent adds an event (with EventType and opaque data), to queue.
- issueEventIsr does the same in ISR context.
- registerHandler registers a handler to receive events of a particular type.
- registerFinalizer does the same for finalizers.
[ ] Why is EvtMgr an EventHandler and EventFinalizer? [ ] Why are separate EventHandler, EventFinalizer methods needed?
At present, it appears that the event manager is basically unused. The only the event manager itself registers for or issues any events. The implemented events include EVT_INIT, EVT_10MS, EVT_1S.
Buffer manager isn’t referenced in EvtMgr.
Buffer Manager
A buffer manager exists to support simple alloc/dealloc with reference counts of buffers. Memory allocation is based on a set of fixed size buffers that can be strung together, if necessary to store larger data sets. So the stored data is not continguous in memory. Currently 32 buffers of 64 bytes are managed.
Methods exist to read out a buffer chain as a continuous string, append data to a buffer and add and remove references.
API seems a bit odd. Buffers are allocated through BufMgr::alloc but freed by using Buffer::rmRef. (Would be better to add an alloc method to Buffer.)
Currently it seems there are no users of the Buffer Manager. Indeed, the Buffer Manager is not linked in to the current application.
Serial Driver
Supports getPort(), read(buf, len) and write(buf, len) on USART devices.
serial_init called by main to initialize ports. port id 0 is set as console port. (Becomes basis of stdio, printf calls)
CLI
There is a basic CLI. It uses stdio, (fgetc, printf, fflush), for input and output. It runs as a task when the default task calls cli_run().
A help command is built in to the command interpreter. A conStats command is supplied by the serial driver. ioTest command performs 1000 writes to the serial port. esp command runs an interactive terminal with ESP8266 until ^C is keyed.
Button
Button.c implements button polling.
Debug support
The debug module has functions to set, clear, pulse the debug GPIO signal. Generally, this is for observation with a logic analyzer.
Timers (BLDC and Servo controls)
(Unimplemented)
SD, FAT Filesystem
(Unimplemented)
Hardware Resources
TIM1 : CH1 - Servo PWM., CH3 input capture? TIM2 : CH1 - CH3 for BLDC drive TIM3 : CH1 - CH4 for BLDC drive TIM4 : CH3, CH4 - Input capture (BNO intn timing?) TIM5 : CH1, CH2 - BLDC drive TIM9 : Timebase source. TIM11 : Not enabled. USART2 : CLI USART6 : ESP8266 connection I2C1 : BNO080 (I2C option) PC0 : BNO_INTN PC1 : BNO_RSTN PC2 : BNO_BOOTN PC3 : BNO_PS1 PC13 : BNO_INTN2 (User button)
SDIO_SD : uSD interface SPI1 : BLDC Driver (old). PA4 : BLDC_EN PC4 : BLDC_CS0 PC5 : BLDC_CS1 USB : USB interface.
PC12 : Debug PA5 : Nucleo LED (is SPI SCLK)
Unallocated: PB2 PB12 PB13 PB14 PC14 PC15
BNO080 Connection (planned)
Changes, Enhancements needed.
[x] In button module, poll button via 10ms event and generate button events.
- Add LED module. [x] Abstract Serial public interface.
- Integrate buffer management with event processing. (Associate buffer with event at issue, rmRef at end of dispatch cycle.)
- Create WiFi process to manage comms with ESP8266.
- Create WiFi Mgr controlled by events.
- Create BNO080 module.