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111 lines
2.8 KiB
111 lines
2.8 KiB
8 years ago
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SBMP library, v1.3
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==================
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This is a reference implementation of SBMP, which should be usable in embedded
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environment.
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The library cosists of a **Framing layer**, **Datagram middleware** and a **Session layer**.
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How to use
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----------
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The framing layer is isolated in the `sbmp_frame` module, and can be used on it's own,
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if sessions are not needed. That gives you reliable data transfer with error detection.
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If you want to *get the most out of SBMP*, use the session layer. Session layer functions are
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namespaced `sbmp_ep_` ("ep" stands for endpoint).
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All header files are included in `sbmp.h`, which is the only file you should
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`#include` in your application.
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Read comments in the examples to see how to use the library.
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Configuration & porting
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-----------------------
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You can customize a lot of aspects of SBMP in `sbmp_config.h`.
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If you included the library as a submodule, and want to avoid manual edits, you can set
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the options using compiler flags (eg. to disable CRC32: `-DSBMP_HAS_CRC32=0`).
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**What to change for Arduino**
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Basically disable all you can in the config file.
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- You don't want `malloc()`
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- Logging is useless if there's only one USART anyway
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- CRC32 can be replaced with XOR if you don't care about reliability that much.
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This gains you a huge size reduction, and the whole library will take only around
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2.5 kB flash and 150 B ram (of course, not including your Rx buffer).
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It works really well for ATmega328P - the usual Arduino chip.
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Example for AVR
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---------------
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This example uses the [AVR C boilerplate](https://github.com/MightyPork/avr-c-boilerplate).
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It's here just to show how to set up SBMP in your AVR application.
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**NOTE:** This example uses static allocation of the struct and buffer.
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If you pass NULLs to the init function, it will `malloc()` it for you
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and return a pointer to the Endpoint.
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```c
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#include <avr/io.h> // register definitions
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#include <avr/interrupt.h> // interrupt vectors
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#include <stdint.h>
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#include <stdbool.h>
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// AVR C boilerplate libs
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#include "lib/iopins.h"
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#include "lib/usart.h"
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// SBMP
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#include "sbmp/sbmp.h"
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// SBMP globals
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#define RXBUF_LEN 128
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static uint8_t rxbuf[RXBUF_LEN];
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static SBMP_Endpoint ep;
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/** USART receive handler */
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ISR(USART_RX_vect)
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{
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// Get the byte and pass it to SBMP
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uint8_t b = usart_rx();
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sbmp_ep_receive(&ep, b); // WARN: This can fail. Should check retval.
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}
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/** Message received from SBMP */
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void message_received(SBMP_Datagram *dg)
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{
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// ...
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}
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int main()
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{
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usart_init(BAUD_115200);
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usart_isr_rx_enable(true); // enable the interrupt
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// init SBMP
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sbmp_ep_init(&ep, rxbuf, RXBUF_LEN, message_received, usart_tx);
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// ...additional SBMP configuration if needed...
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// enable rx, tx
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sbmp_ep_enable(&ep, true);
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// globally enable interrupts (for the USART_RX handler)
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sei();
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while (1) {
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// ... do stuff
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}
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}
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```
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