half-duplex-protocol

A low level communication protocol, using a single IO/pin for sending data, and another IO/pin for receiving data.

Bitrate/Frequency

At the current state the protocol can only read 500hz to 1MHz (depending on how precise the timers on the device can be). This is because the program uses milliseconds as base time. May be upgraded in the future.

Usage

Send data

#include "protocol.h"
...
hdp_initialize();

/* You can set a bitrate manually but it's 
 * prefered to use this in case more bitrates get added */
hdp_bitrate = hdp_get_nearest_bitrate(500);

hdp_data_set_byte(hdp_send_data, DATA_BYTES_RESERVED, 0, 'h');
hdp_data_set_byte(hdp_send_data, DATA_BYTES_RESERVED, 1, 'e');
hdp_data_set_byte(hdp_send_data, DATA_BYTES_RESERVED, 2, 'l');
hdp_data_set_byte(hdp_send_data, DATA_BYTES_RESERVED, 3, 'l');
hdp_data_set_byte(hdp_send_data, DATA_BYTES_RESERVED, 4, 'o');

hdp_transmit();

You can also modify hdp_send_data directly or use hdp_data_set_bit where you can set bits through the entire transmit data. e.g.

/* Set bit index 12 (from left) to 1. 
 * 00000000|00001000|000000... */
hdp_data_set_bit(hdp_send_data, DATA_BYTES_RESERVED, 12, 1);

Recieve data

To recieve data, the code below can be used:

#include "protocol.h"
...
hdp_initialize();
hdp_recieve();
printf("Data: %s\n", hdp_recieve_data);

The code will stall until it gets a response. A timeout timer may be added in the future.