a379eb7bf6
This commit introduces support for Dallas Semiconductor (DS) 1-wire compliant device support using an available UART device. The principle of operation is described in the following Application note by Maxim Electronics: https://www.maximintegrated.com/en/app-notes/index.mvp/id/214 with help (1-wire search) from: https://www.maximintegrated.com/en/app-notes/index.mvp/id/187 It has been tested on Galileo 2 and Edison, with 2 DS 1-wire devices, the DS18B20 and DS2413 connected to the bus. A UPM driver for the DS2413 is already complete and a PR will be submitted after this one. It is important that you use a UART with CMOS/TTL level voltages (3.3v/5v) RX and TX lines. DO NOT use standard RS232 level voltages or you are going to have a bad day. In order for this to work, a simple interface circuit, using a single diode must be constructed: (forgive my "Asciihematic" :) -| U| A| TX---|<--+ R| | T| RX-------o--------o 1-wire data bus -| The diode on TX is a 1N4148 (cheap and common), with the cathode connected to TX, and the anode connected to RX and the 1-wire data line. The 1-wire data line requires a pull-up resistor, as the DS 1-wire spec requires. 4.7-5K is typical for DS 1-wire buses. NOTE: DHT-type (temp/humidity sensor) 1-wire devices ARE NOT DS 1-wire compliant, and will not work with this code/circuit unfortunately. Also note, this will use up one of your UARTs, which cannot be used for any other purpose (ie: to access true UART-type serial devices). You can however, connect as many DS 1-wire devices as feasible to this UART, as it will function as a DS 1-wire bus master. Signed-off-by: Jon Trulson <jtrulson@ics.com> Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
94 lines
3.0 KiB
C
94 lines
3.0 KiB
C
/*
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* Author: Jon Trulson <jtrulson@ics.com>
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* Copyright (c) 2016 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include "stdio.h"
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//! [Interesting]
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#include "mraa.h"
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int
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main(int argc, char** argv)
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{
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mraa_uart_ow_context uart;
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uart = mraa_uart_ow_init(0);
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if (!uart) {
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printf("mraa_uart_ow_init() failed\n");
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return 1;
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}
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// Reset the ow bus and see if anything is present
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mraa_result_t rv;
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if ((rv = mraa_uart_ow_reset(uart)) == MRAA_SUCCESS) {
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printf("Reset succeeded, device(s) detected!\n");
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} else {
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printf("Reset failed, returned %d. No devices on bus?\n", rv);
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return 1;
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}
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printf("Looking for devices...\n");
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uint8_t id[MRAA_UART_OW_ROMCODE_SIZE];
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/* we are essentially doing a binary tree search through the 64
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* bit address space. id is modified during this search, and will
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* be set to the valid rom code for each device found.
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*/
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uint8_t count = 0;
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// start the search from scratch
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uint8_t result = mraa_uart_ow_rom_search(uart, 1, id);
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if (result == MRAA_ERROR_UART_OW_NO_DEVICES) {
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printf("No devices detected.\n");
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return 1;
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}
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if (result == MRAA_ERROR_UART_OW_DATA_ERROR) {
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printf("Bus/Data error.\n");
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return 1;
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}
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while (result == MRAA_SUCCESS) {
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/* The first byte (id[0]]) is the device type (family) code.
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* The last byte (id[7]) is the rom code CRC value. The
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* intervening bytes (id[1]-id[6]) are the unique 48 bit
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* device ID.
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*/
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printf("Device %02d Type 0x%02x ID %02x%02x%02x%02x%02x%02x CRC 0x%02x\n", count, id[0],
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id[6], id[5], id[4], id[3], id[2], id[1], id[7]);
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count++;
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// continue the search with start argument set to 0
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result = mraa_uart_ow_rom_search(uart, 0, id);
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}
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printf("Exiting...\n");
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mraa_uart_ow_stop(uart);
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return 0;
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}
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//! [Interesting]
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