DS1921-Thermochron(3)

🦋 DS1921-Thermochron — the temperature-logging iButton 💖

okay so bestie, welcome to DS1921-Thermochron(3) from the One-Wire File System ✨ This is part 1 of 2, so don't go anywhere, there's more coming.

DS1921 — Thermochron temperature logging iButton. that's the whole name, that's the whole vibe 🎀

---

🌸 SYNOPSIS

Temperature logging iButton. that's it, that's the summary 💅

21 [.]XXXXXXXXXXXX[XX][/[
about/[measuring| resolution| samples| templow| temphigh| version] |
clock/[date| running| udate] |
histotgram/[counts[0-62|ALL]| gap| temperature[counts[0-62|ALL]] |
log[date[0-2047|ALL]| elements| temperature[0-2047|ALL]|
udate[0-2047|ALL]] |
memory |
mission/[date| delay| easystart| frequency| rollover| running| samples|
sampling| udate] |
overtemp/[date[0-11|ALL]| elements| end[0-11|ALL]| count[0-11|ALL]|
temperature[0-11|ALL]| udate[0-11|ALL]] |
pages/page.[0-15|ALL] |
temperature |
undertemp/[date[0-11|ALL]| elements|end[0-11|ALL]| count[0-11|ALL]|
temperature[0-11|ALL]| udate[0-11|ALL]] | address | crc8 | id | locator
| r_address | r_id | r_locator | type ]]

---

👑 FAMILY CODE

21

that's the family code, no cap. it's literally how you know it's a Thermochron and not some other iButton out here living its life 🌈

---

✨ SPECIAL PROPERTIES ✨

these are the ones that make the DS1921 do its little temperature-logging thing. so much main character energy, honestly 🫶

💜 about/

about/measuring

read-only, yes-no

Is this DS1921 currently measuring a temperature? yes or no, that's the whole question bestie 💀

about/resolution

read-only, floating point

What is the resolution of the temperature measurments (in the current temperature scale). tiny little steps, that's what resolution is ✨

about/samples

read-only, unsigned integer

How many total temperature measurements has this DS1921 performed? it's been keeping count the whole time, obsessed 😭

about/temphigh

read-only, floating point

Highest temperature this DS1921 can measure (in the current temperature scale). it has a ceiling, it's not gonna do everything for you 🥵

about/templow

read-only, floating point

Lowest temperature this DS1921 can measure (in the current temperature scale). and it has a floor too, boundaries are healthy 💅

about/version

read-only, ascii

Specific version of this DS1921. every girlie has a version number and hers is in here 🌸

🕰️ clock/

clock/date

read-write, ascii

26 character date representation of the internal time stored in this DS1921. Increments once per second while clock/running.

Setting date to a null string will put the current system time.

Accepted date formats are:

Sat[urday] March 12 12:23:59 2001
Apr[il] 4 9:34:56 2002
3/23/04 23:34:57
current locale setting (your system's format)

pick your fave, they all work, it's giving flexible 💖

clock/running

read-write, yes-no

Whether the internal clock is running. This can be explicitly set, and is automatically started by setting clock/date or clock/udate or by starting a mission with mission/easystart or mission/frequency.

The main reason to stop the clock is to conserve the internal battery. The clock cannot be stopped during a mission, and the clock is essential for a mission.

so like, clock = whole entire point of a mission. do not come for her 💀

clock/udate

read-write, unsigned integer

A numeric representation of clock/date. The number of seconds in UNIX time (since Jan 1, 1970). numbers girlies rise up 🔥

📊 histogram/

histogram/counts.0 ... histogram/counts.62 histogram/counts.ALL

read-only, unsigned integer

The number of samples in the current mission whose temperature fell within the histogram/temperature to histogram/temperature+histogram/gap range. it's counting, that's the job ✨

histogram/elements

read-only, unsigned integer

The number of bins in the histogram. Always 63. always. 63. no notes 🎀

histogram/gap

read-only, floating point

The size of the histogram bin. Depends on the Thermochron version ( about/version ) and is usually 4 times about/resolution.

Given in the current temperatature scale.

histogram/temperature.0 ... histogram/temperature.62 histogram/temperature.ALL

read-only, floating point

Lower limit of the temperature range for the corresponding histogram bin. In the current temperature scale. that's the floor of each lil bin 💜

📓 log/

log/date.0 ... log/date.2047 log/date.ALL

read-only, ascii

Date that the corresponding log/temperature was taken, in ascii format. (See clock/date for more on the format). The number of valid entries is actually log/elements since the log may not be full.

mission/samples gives the total number of samples that have been taken but there is only room in the log for 2048 entries. Once the log is full, mission/rollover determines the Thermochron's behavior.

• If mission/rollover is false(0), the log will hold the first 2048 samples and log/date.0 will always be the same as mission/date
• If mission/rollover is true (1) then the log will hold the last 2048 samples and the entries will be shifted down with each new sample.

Note the OWFS code "untwists" the rollover behavior. The data will always be a linear array of earliest to latest.

ALL is the all data elements comma separated.

log/elements

read-only, unsigned integer

Number of valid entries in the log. OWFS offers the full 2048 values in the log memory, but not that many samples may yet have been taken. log/elements will range from 0 to 2048 and always be less than or equal to mission/samples. math is mathing 📐

log/temperature.0 ... log/temperature.2047 log/temperature.ALL

read-write, floating point

The temperature readings (in the current temperature scale) that correspond to the log/date sample. See log/date for details on the indexing scheme and rollover behavior. 🌡️

log/udate.0 ... log/udate.2047 log/udate.ALL

read-write, unsigned integer

A numeric representation of log/date. The number of seconds in UNIX time (since Jan 1, 1970).

💾 memory

read-write, binary

User available storage space. 512 bytes. Can also be accessed as 16 pages of 32 bytes with the pages/page.x properties. yes bestie you get 512 whole bytes, spend them wisely 🫶

🥵 overtemp/ and 🥶 undertemp/

overtemp/count.0 ... overtemp/count.11 overtemp/count.ALL

undertemp/count.0 ... undertemp/count.11 undertemp/count.ALL

read-only, unsigned integer

Number of sampling periods that the Thermochron stayed out of range during a mission. Each sampling period is mission/frequency minutes long. she's counting every single time you left her hanging 😭

overtemp/end.0 ... overtemp/end.11 overtemp/end.ALL

undertemp/end.0 ... undertemp/end.11 undertemp/end.ALL

read-only, ascii

End of time that the Thermochron went out of range during the current mission. See clock/date for format.

Each period can be up to 255 samples in length, and span the time overtemp/date to overtemp/end ( or undertemp/date to undertemp/end ). ⏳

overtemp/date.0 ... overtemp/date.11 overtemp/date.ALL

undertemp/date.0 ... undertemp/date.11 undertemp/date.ALL

read-only, ascii

Time that the Thermochron went out of range during the current mission. See clock/date for format. the moment it all went wrong, timestamped 💀

overtemp/elements

undertemp/elements

read-only, unsigned integer

Number of entries (0 to 12) in the overtemp or undertemp array.

overtemp/temperature

undertemp/temperature

read-write, floating point

Temperature limit to trigger alarm and error log. overtemp/temperature gives upper limit and undertemp/temperature gives lower limit.

In current temperature scale. set your boundaries bestie, boundaries are self care 💅

overtemp/udate.0 ... overtemp/udate.11 overtemp/udate.ALL

undertemp/udate.0 ... undertemp/udate.11 undertemp/udate.ALL

read-only, unsigned integer

A numeric representation of overtemp/date or undertemp/date. The number of seconds in UNIX time (since Jan 1, 1970).

📄 pages/

pages/page.0 ... pages/page.15 pages/page.ALL

read-write, binary

Memory is split into 16 pages of 32 bytes each. User available. The log memory, register banks and histogram data area are all separate from this memory area.

ALL is an aggregate of the pages. Each page is accessed sequentially. 16 pages, 32 bytes, all yours 🎀

🌡️ temperature

read-only, floating point

Last temperature explicitly requested. Only available when the mission is not in progress. Value returned in in the current temperature scale. she's only available when she's not busy, respect the schedule ✨

---

⭐ STANDARD PROPERTIES ⭐

every 1-wire deviceie has these, it's the shared lore 🦋

address, r_address

read-only, ascii

The entire 64-bit unique ID. Given as upper case hexadecimal digits (0-9A-F).

address starts with the family code.

r_address is the address in reverse order, which is often used in other applications and labeling. backwards but make it iconic 👑

crc8

read-only, ascii

The 8-bit error correction portion. Uses cyclic redundancy check. Computed from the preceding 56 bits of the unique ID number. Given as upper case hexadecimal digits (0-9A-F). she checks herself before she wrecks herself 💅

family

read-only, ascii

The 8-bit family code. Unique to each type of device. Given as upper case hexadecimal digits (0-9A-F).

id, r_id

read-only, ascii

The 48-bit middle portion of the unique ID number. Does not include the family code or CRC. Given as upper case hexadecimal digits (0-9A-F).

r_id is the id in reverse order, which is often used in other applications and labeling.

locator, r_locator

read-only, ascii

Uses an extension of the 1-wire design from iButtonLink company that associated 1-wire physical connections with a unique 1-wire code. If the connection is behind a Link Locator the locator will show a unique 8-byte number (16 character hexadecimal) starting with family code FE.

If no Link Locator is between the device and the master, the locator field will be all FF.

r_locator is the locator in reverse order. 📍

present (DEPRECATED)

read-only, yes-no

Is the device currently present on the 1-wire bus?

ngl bestie this one is DEPRECATED. it's giving legacy, it's giving old money, but the manual says deprecated so we're saying deprecated 🙈

type

read-only, ascii

Part name assigned by Dallas Semi. E.g. DS2401 Alternative packaging (iButton vs chip) will not be distiguished. a chip and an iButton are the same girl in different outfits, we don't discriminate 🌈

---

🚨 ALARMS

None.

that's right bestie. no alarms. she's chill like that 😌💖

---

DESCRIPTION 💖

1-Wire ⚡

okay so 1-wire is a wiring protocol and a whole series of devices designed and manufactured by Dallas Semiconductor, Inc. The bus is a low-power, low-speed, low-connector scheme where the data line can also provide power. No cap.

Every device gets a unique and unalterable number during manufacture. There's a wide variety of devices, including memory, sensors (humidity, temperature, voltage, contact, current), switches, timers and data loggers. More complex devices (like thermocouple sensors) can be built with these basic devices. There are also 1-wire devices that have encryption included. 💅

The 1-wire scheme uses a single bus master and multiple slaves on the same wire. The bus master initiates all communication. The slaves can be individually discovered and addressed using their unique ID.

Bus masters come in a variety of configurations including serial, parallel, i2c, network or USB adapters. ✨

OWFS design 🌈

OWFS is a suite of programs that's designed to make the 1-wire bus and its devices easily accessible. The underlying principle is to create a virtual filesystem, with the unique ID being the directory, and the individual properties of the device are represented as simple files that can be read and written.

Details of the individual slave or master design are hidden behind a consistent interface. The goal is to provide an easy set of tools for a software designer to create monitoring or control applications. There are some performance enhancements in the implementation, including data caching, parallel access to bus masters, and aggregation of device communication. Still the fundamental goal has been ease of use, flexibility and correctness rather than speed. Periodt.

DS1921 Thermochron 🌡️

The DS1921 (3) is an iButton device with many intriguing functions. Essentially it monitors temperature, giving both a log of readings, and a histogram of temperature ranges. The specification is somewhat complex, but OWFS hides many of the implementation details. 🙈

While on a mission the DS1921 (3) records temperature readings in a 2048-sample log and adds them to a 62-bin histogram. Obsessed.

ADDRESSING 📬

All 1-wire devices are factory assigned a unique 64-bit address. This address is of the form:

• Family Code — 8 bits
• Address — 48 bits
• CRC — 8 bits

Addressing under OWFS is in hexadecimal, of form:

01.123456789ABC

where 01 is an example 8-bit family code, and 12345678ABC is an example 48 bit address.

The dot is optional, and the CRC code can be included. If included, it must be correct. fr fr, it has to be correct.

DATASHEET 📄

• http://pdfserv.maxim-ic.com/en/ds/DS2438.pdf
• http://pdfserv.maxim-ic.com/en/an/humsensor.pdf

SEE ALSO 👀

Programs 💻

• owfs (1), owhttpd (1), owftpd (1), owserver (1), owdir (1), owread (1), owwrite (1), owpresent (1), owtap (1)

Configuration and testing 🧪

• owfs (5), owtap (1), owmon (1)

Language bindings 🗣️

• owtcl (3), owperl (3), owcapi (3)

Clocks ⏰

• DS1427 (3), DS1904 (3), DS1994 (3), DS2404 (3), DS2404S (3), DS2415 (3), DS2417 (3)

ID 🆔

• DS2401 (3), DS2411 (3), DS1990A (3)

Memory 💾

• DS1982 (3), DS1985 (3), DS1986 (3), DS1991 (3), DS1992 (3), DS1993 (3), DS1995 (3), DS1996 (3), DS2430A (3), DS2431 (3), DS2433 (3), DS2502 (3), DS2506 (3), DS28E04 (3), DS28EC20 (3)

Switches 🔘

• DS2405 (3), DS2406 (3), DS2408 (3), DS2409 (3), DS2413 (3), DS28EA00 (3), InfernoEmbedded (3)

Temperature 🌡️

• DS1822 (3), DS1825 (3), DS1820 (3), DS18B20 (3), DS18S20 (3), DS1920 (3), DS1921 (3), DS1821 (3), DS28EA00 (3), DS28E04 (3), EDS0064 (3), EDS0065 (3), EDS0066 (3), EDS0067 (3), EDS0068 (3), EDS0071 (3), EDS0072 (3), MAX31826 (3)

Humidity 💧

• DS1922 (3), DS2438 (3), EDS0065 (3), EDS0068 (3)

Voltage ⚡

• DS2450 (3)

Resistance 🔌

• DS2890 (3)

Multifunction (current, voltage, temperature) 🔥

• DS2436 (3), DS2437 (3), DS2438 (3), DS2751 (3), DS2755 (3), DS2756 (3), DS2760 (3), DS2770 (3), DS2780 (3), DS2781 (3), DS2788 (3), DS2784 (3)

Counter 🔢

• DS2423 (3)

LCD Screen 🖥️

• LCD (3), DS2408 (3)

Crypto 🔐

• DS1977 (3)

Pressure 🌬️

• DS2406 (3), TAI8570 (3), EDS0066 (3), EDS0068 (3)

Moisture 💦

• EEEF (3), DS2438 (3)

AVAILABILITY 🛒

• http://www.owfs.org

AUTHOR 👑

Paul Alfille (paul.alfille@gmail.com)

---

💖 That's the tea from the OWFS Manpage, 2005 edition — DS1921-Thermochron(3), out. Byeee! 💅✨