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Add more documentation for onewire.h

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This commit is contained in:
Alex Stewart 2016-03-17 19:24:29 -07:00
parent 9b49b426f6
commit 9c37da6834
2 changed files with 217 additions and 110 deletions
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53
extras/onewire/onewire.c
View file

@ -3,6 +3,10 @@
#include "task.h"
#include "esp/gpio.h"
#define ONEWIRE_SELECT_ROM 0x55
#define ONEWIRE_SKIP_ROM 0xcc
#define ONEWIRE_SEARCH 0xf0
// Waits up to `max_wait` microseconds for the specified pin to go high.
// Returns true if successful, false if the bus never comes high (likely
// shorted).
@ -48,9 +52,9 @@ bool onewire_reset(int pin) {
return r;
}
static bool _onewire_write_bit(int pin, uint8_t v) {
static bool _onewire_write_bit(int pin, bool v) {
if (!_onewire_wait_for_bus(pin, 10)) return false;
if (v & 1) {
if (v) {
taskENTER_CRITICAL();
gpio_write(pin, 0); // drive output low
sdk_os_delay_us(10);
@ -94,7 +98,7 @@ bool onewire_write(int pin, uint8_t v) {
uint8_t bitMask;
for (bitMask = 0x01; bitMask; bitMask <<= 1) {
if (!_onewire_write_bit(pin, (bitMask & v)?1:0)) {
if (!_onewire_write_bit(pin, (bitMask & v))) {
return false;
}
}
@ -142,28 +146,36 @@ bool onewire_read_bytes(int pin, uint8_t *buf, size_t count) {
return true;
}
// Do a ROM select
//
void onewire_select(int pin, onewire_addr_t rom) {
bool onewire_select(int pin, onewire_addr_t addr) {
uint8_t i;
onewire_write(pin, 0x55); // Choose ROM
if (!onewire_write(pin, ONEWIRE_SELECT_ROM)) {
return false;
}
for (i = 0; i < 8; i++) {
onewire_write(pin, rom & 0xff);
rom >>= 8;
if (!onewire_write(pin, addr & 0xff)) {
return false;
}
addr >>= 8;
}
return true;
}
// Do a ROM skip
//
void onewire_skip_rom(int pin) {
onewire_write(pin, 0xCC); // Skip ROM
bool onewire_skip_rom(int pin) {
return onewire_write(pin, ONEWIRE_SKIP_ROM);
}
void onewire_power(int pin) {
bool onewire_power(int pin) {
// Make sure the bus is not being held low before driving it high, or we
// may end up shorting ourselves out.
if (!_onewire_wait_for_bus(pin, 10)) return false;
gpio_enable(pin, GPIO_OUTPUT);
gpio_write(pin, 1);
return true;
}
void onewire_depower(int pin) {
@ -175,9 +187,6 @@ void onewire_search_start(onewire_search_t *search) {
memset(search, 0, sizeof(*search));
}
// Setup the search to find the device type 'family_code' on the next call
// to search(*newAddr) if it is present.
//
void onewire_search_prefix(onewire_search_t *search, uint8_t family_code) {
uint8_t i;
@ -209,8 +218,8 @@ onewire_addr_t onewire_search_next(onewire_search_t *search, int pin) {
int rom_byte_number;
uint8_t id_bit, cmp_id_bit;
onewire_addr_t addr;
unsigned char rom_byte_mask, search_direction;
unsigned char rom_byte_mask;
bool search_direction;
// initialize for search
id_bit_number = 1;
@ -230,7 +239,7 @@ onewire_addr_t onewire_search_next(onewire_search_t *search, int pin) {
}
// issue the search command
onewire_write(pin, 0xF0);
onewire_write(pin, ONEWIRE_SEARCH);
// loop to do the search
do {
@ -259,14 +268,14 @@ onewire_addr_t onewire_search_next(onewire_search_t *search, int pin) {
}
// if 0 was picked then record its position in LastZero
if (search_direction == 0) {
if (!search_direction) {
last_zero = id_bit_number;
}
}
// set or clear the bit in the ROM byte rom_byte_number
// with mask rom_byte_mask
if (search_direction == 1) {
if (search_direction) {
search->rom_no[rom_byte_number] |= rom_byte_mask;
} else {
search->rom_no[rom_byte_number] &= ~rom_byte_mask;

274
extras/onewire/onewire.h
View file

@ -4,134 +4,232 @@
#include <espressif/esp_misc.h> // sdk_os_delay_us
#include "FreeRTOS.h"
// 1 for keeping the parasitic power on H
#define ONEWIRE_DEFAULT_POWER 1
/** @file onewire.h
*
* Routines to access devices using the Dallas Semiconductor 1-Wire(tm)
* protocol.
*/
// Maximum number of devices.
#define ONEWIRE_NUM 20
// You can exclude certain features from OneWire. In theory, this
// might save some space. In practice, the compiler automatically
// removes unused code (technically, the linker, using -fdata-sections
// and -ffunction-sections when compiling, and Wl,--gc-sections
// when linking), so most of these will not result in any code size
// reduction. Well, unless you try to use the missing features
// and redesign your program to not need them! ONEWIRE_CRC8_TABLE
// is the exception, because it selects a fast but large algorithm
// or a small but slow algorithm.
// Select the table-lookup method of computing the 8-bit CRC
// by setting this to 1. The lookup table enlarges code size by
// about 250 bytes. It does NOT consume RAM (but did in very
// old versions of OneWire). If you disable this, a slower
// but very compact algorithm is used.
/** Select the table-lookup method of computing the 8-bit CRC
* by setting this to 1 during compilation. The lookup table enlarges code
* size by about 250 bytes. By default, a slower but very compact algorithm
* is used.
*/
#ifndef ONEWIRE_CRC8_TABLE
#define ONEWIRE_CRC8_TABLE 0
#endif
/** Type used to hold all 1-Wire device ROM addresses (64-bit) */
typedef uint64_t onewire_addr_t;
/** Structure to contain the current state for onewire_search_next(), etc */
typedef struct {
uint8_t rom_no[8];
uint8_t last_discrepancy;
bool last_device_found;
} onewire_search_t;
// The following is an invalid ROM address that will never occur in a device
// (CRC mismatch), and so can be useful as an indicator for "no-such-device",
// etc.
/** ::ONEWIRE_NONE is an invalid ROM address that will never occur in a device
* (CRC mismatch), and so can be useful as an indicator for "no-such-device",
* etc.
*/
#define ONEWIRE_NONE ((onewire_addr_t)(0xffffffffffffffffLL))
// Perform a 1-Wire reset cycle. Returns 1 if a device responds
// with a presence pulse. Returns 0 if there is no device or the
// bus is shorted or otherwise held low for more than 250uS
/** Perform a 1-Wire reset cycle.
*
* @param pin The GPIO pin connected to the 1-Wire bus.
*
* @returns `true` if at least one device responds with a presence pulse,
* `false` if no devices were detected (or the bus is shorted, etc)
*/
bool onewire_reset(int pin);
// Issue a 1-Wire rom select command, you do the reset first.
void onewire_select(int pin, const onewire_addr_t rom);
/** Issue a 1-Wire rom select command to select a particular device.
*
* It is necessary to call onewire_reset() before calling this function.
*
* @param pin The GPIO pin connected to the 1-Wire bus.
* @param addr The ROM address of the device to select
*
* @returns `true` if the "ROM select" command could be succesfully issued,
* `false` if there was an error.
*/
bool onewire_select(int pin, const onewire_addr_t addr);
// Issue a 1-Wire rom skip command, to address all on bus.
void onewire_skip_rom(int pin);
/** Issue a 1-Wire "skip ROM" command to select *all* devices on the bus.
*
* It is necessary to call onewire_reset() before calling this function.
*
* @param pin The GPIO pin connected to the 1-Wire bus.
*
* @returns `true` if the "skip ROM" command could be succesfully issued,
* `false` if there was an error.
*/
bool onewire_skip_rom(int pin);
// Write a byte. The writing code uses open-drain mode and expects the pullup
// resistor to pull the line high when not driven low. If you need strong
// power after the write (e.g. DS18B20 in parasite power mode) then call
// onewire_power() after this is complete to actively drive the line high.
// Returns true if successful, false on error.
/** Write a byte on the onewire bus.
*
* The writing code uses open-drain mode and expects the pullup resistor to
* pull the line high when not driven low. If you need strong power after the
* write (e.g. DS18B20 in parasite power mode) then call onewire_power() after
* this is complete to actively drive the line high.
*
* @param pin The GPIO pin connected to the 1-Wire bus.
* @param v The byte value to write
*
* @returns `true` if successful, `false` on error.
*/
bool onewire_write(int pin, uint8_t v);
/** Write multiple bytes on the 1-Wire bus.
*
* See onewire_write() for more info.
*
* @param pin The GPIO pin connected to the 1-Wire bus.
* @param buf A pointer to the buffer of bytes to be written
* @param count Number of bytes to write
*
* @returns `true` if all bytes written successfully, `false` on error.
*/
bool onewire_write_bytes(int pin, const uint8_t *buf, size_t count);
// Read a byte.
// Returns the read byte on success, negative value on error.
/** Read a byte from a 1-Wire device.
*
* @param pin The GPIO pin connected to the 1-Wire bus.
*
* @returns the read byte on success, negative value on error.
*/
int onewire_read(int pin);
/** Read multiple bytes from a 1-Wire device.
*
* @param pin The GPIO pin connected to the 1-Wire bus.
* @param buf A pointer to the buffer to contain the read bytes
* @param count Number of bytes to read
*
* @returns `true` on success, `false` on error.
*/
bool onewire_read_bytes(int pin, uint8_t *buf, size_t count);
// Actively drive the bus high to provide extra power for certain operations of
// parasitically-powered devices.
void onewire_power(int pin);
/** Actively drive the bus high to provide extra power for certain operations
* of parasitically-powered devices.
*
* For parasitically-powered devices which need more power than can be
* provided via the normal pull-up resistor, it may be necessary for some
* operations to drive the bus actively high. This function can be used to
* perform that operation.
*
* The bus can be depowered once it is no longer needed by calling
* onewire_depower(), or it will be depowered automatically the next time
* onewire_reset() is called to start another command.
*
* Note: Make sure the device(s) you are powering will not pull more current
* than the ESP8266 is able to supply via its GPIO pins (this is especially
* important when multiple devices are on the same bus and they are all
* performing a power-intensive operation at the same time (i.e. multiple
* DS18B20 sensors, which have all been given a "convert T" operation by using
* onewire_skip_rom())).
*
* Note: This routine will check to make sure that the bus is already high
* before driving it, to make sure it doesn't attempt to drive it high while
* something else is pulling it low (which could cause a reset or damage the
* ESP8266).
*
* @param pin The GPIO pin connected to the 1-Wire bus.
*
* @returns `true` on success, `false` on error.
*/
bool onewire_power(int pin);
// Stop forcing power onto the bus. You only need to do this if
// you previously called onewire_power() to drive the bus high and now want to
// allow it to float instead. Note that onewire_reset() will also
// automatically depower the bus first, so you do not need to call this first
// if you just want to start a new operation.
/** Stop forcing power onto the bus.
*
* You only need to do this if you previously called onewire_power() to drive
* the bus high and now want to allow it to float instead. Note that
* onewire_reset() will also automatically depower the bus first, so you do
* not need to call this first if you just want to start a new operation.
*
* @param pin The GPIO pin connected to the 1-Wire bus.
*/
void onewire_depower(int pin);
// Clear the search state so that if will start from the beginning again.
/** Clear the search state so that it will start from the beginning on the next
* call to onewire_search_next().
*
* @param search The onewire_search_t structure to reset.
*/
void onewire_search_start(onewire_search_t *search);
// Setup the search to find the device type 'family_code' on the next call
// to search(*newAddr) if it is present.
/** Setup the search to search for devices with the specified "family code".
*
* @param search The onewire_search_t structure to update.
* @param family_code The "family code" to search for.
*/
void onewire_search_prefix(onewire_search_t *search, uint8_t family_code);
// Look for the next device. Returns the address of the next device on the bus,
// or ONEWIRE_NONE if there is no next address. ONEWIRE_NONE might mean that
// the bus is shorted, there are no devices, or you have already retrieved all
// of them. It might be a good idea to check the CRC to make sure you didn't
// get garbage. The order is deterministic. You will always get the same
// devices in the same order.
/** Search for the next device on the bus.
*
* The order of returned device addresses is deterministic. You will always
* get the same devices in the same order.
*
* @returns the address of the next device on the bus, or ::ONEWIRE_NONE if
* there is no next address. ::ONEWIRE_NONE might also mean that the bus is
* shorted, there are no devices, or you have already retrieved all of them.
*
* It might be a good idea to check the CRC to make sure you didn't get
* garbage.
*/
onewire_addr_t onewire_search_next(onewire_search_t *search, int pin);
// Compute a Dallas Semiconductor 8 bit CRC, these are used in the
// ROM and scratchpad registers.
/** Compute a Dallas Semiconductor 8 bit CRC.
*
* These are used in the ROM address and scratchpad registers to verify the
* transmitted data is correct.
*/
uint8_t onewire_crc8(const uint8_t *data, uint8_t len);
// Compute the 1-Wire CRC16 and compare it against the received CRC.
// Example usage (reading a DS2408):
// // Put everything in a buffer so we can compute the CRC easily.
// uint8_t buf[13];
// buf[0] = 0xF0; // Read PIO Registers
// buf[1] = 0x88; // LSB address
// buf[2] = 0x00; // MSB address
// WriteBytes(net, buf, 3); // Write 3 cmd bytes
// ReadBytes(net, buf+3, 10); // Read 6 data bytes, 2 0xFF, 2 CRC16
// if (!CheckCRC16(buf, 11, &buf[11])) {
// // Handle error.
// }
//
// @param input - Array of bytes to checksum.
// @param len - How many bytes to use.
// @param inverted_crc - The two CRC16 bytes in the received data.
// This should just point into the received data,
// *not* at a 16-bit integer.
// @param crc_iv - The crc starting value (optional)
// @return True, iff the CRC matches.
/** Compute the 1-Wire CRC16 and compare it against the received CRC.
*
* Example usage (reading a DS2408):
* @code
* // Put everything in a buffer so we can compute the CRC easily.
* uint8_t buf[13];
* buf[0] = 0xF0; // Read PIO Registers
* buf[1] = 0x88; // LSB address
* buf[2] = 0x00; // MSB address
* onewire_write_bytes(pin, buf, 3); // Write 3 cmd bytes
* onewire_read_bytes(pin, buf+3, 10); // Read 6 data bytes, 2 0xFF, 2 CRC16
* if (!onewire_check_crc16(buf, 11, &buf[11])) {
* // TODO: Handle error.
* }
* @endcode
*
* @param input Array of bytes to checksum.
* @param len Number of bytes in `input`
* @param inverted_crc The two CRC16 bytes in the received data.
* This should just point into the received data,
* *not* at a 16-bit integer.
* @param crc_iv The crc starting value (optional)
*
* @returns `true` if the CRC matches, `false` otherwise.
*/
bool onewire_check_crc16(const uint8_t* input, size_t len, const uint8_t* inverted_crc, uint16_t crc_iv);
// Compute a Dallas Semiconductor 16 bit CRC. This is required to check
// the integrity of data received from many 1-Wire devices. Note that the
// CRC computed here is *not* what you'll get from the 1-Wire network,
// for two reasons:
// 1) The CRC is transmitted bitwise inverted.
// 2) Depending on the endian-ness of your processor, the binary
// representation of the two-byte return value may have a different
// byte order than the two bytes you get from 1-Wire.
// @param input - Array of bytes to checksum.
// @param len - How many bytes to use.
// @param crc_iv - The crc starting value (optional)
// @return The CRC16, as defined by Dallas Semiconductor.
/** Compute a Dallas Semiconductor 16 bit CRC.
*
* This is required to check the integrity of data received from many 1-Wire
* devices. Note that the CRC computed here is *not* what you'll get from the
* 1-Wire network, for two reasons:
* 1. The CRC is transmitted bitwise inverted.
* 2. Depending on the endian-ness of your processor, the binary
* representation of the two-byte return value may have a different
* byte order than the two bytes you get from 1-Wire.
*
* @param input Array of bytes to checksum.
* @param len How many bytes are in `input`.
* @param crc_iv The crc starting value (optional)
*
* @returns the CRC16, as defined by Dallas Semiconductor.
*/
uint16_t onewire_crc16(const uint8_t* input, size_t len, uint16_t crc_iv);
#endif