12/25/2023 0 Comments 24 hour utc clock ebayIn October, on first Sunday, is DST after 2 am If (month = 4 & day firstSundayInOctober) In April, if not yet first Sunday, still DST start it up)įor (int digit = 0 digit = 5 & month = 11) SendByte (MAX7219_REG_SHUTDOWN, 1) // not in shutdown mode (ie. SendByte (MAX7219_REG_INTENSITY, 10) // character intensity: range: 0 to 15 SendByte (MAX7219_REG_DISPLAYTEST, 0) // no display test SendByte (MAX7219_REG_DECODEMODE, 0xFF) // use digits (not bit patterns) SendByte (MAX7219_REG_SCANLIMIT, 7) // show 6 digits set the data rate for the SoftwareSerial port Open serial communications and wait for port to open: Void sendByte (const byte reg, const byte data) send a digit or other data to the MAX7219 how much serial data we expect before a newline codes 1 to 8 are digit positions 1 to 8Ĭonst byte MAX7219_REG_DISPLAYTEST = 0xF The decimal point in the “blank” digit (next to the P) is on if we have a GPS fix, otherwise off. The time is shown as a 12-hour clock with the final digit being “P” for PM. Then the time is adjusted by the time-zone, and then daylight saving based on the date from the GPS. I use a regular expression to parse the GPS data because I was too lazy to work out a more sophisticated way. The main loop is simply the standard “get data from serial and buffer it” stuff. For us right now, from the first Sunday in April to the first Sunday in October, it is not daylight savings time. You may need to adjust the calculations depending on the local rules. The code is below, if you want to reproduce it.Ī fair bit of code is working out whether it is daylight savings time or not. They put out around 3.2V, which is enough for the processor (which is running at 8 MHz on the internal oscillator) and apparently sufficient for the GPS. The whole thing is powered by 2 x AA alkaline batteries. (1.5K and 10K and divides 3.2V into 2.8V at the join of the resistors, with 10K being the one going to Gnd). The Rx line on the GPS is supposed to be held high, so I used a voltage divider (two resistors) to get around 2.8V from the Vcc line on the RBBB. Inside is a Real Bare Bones Board (from Modern Device): The photo doesn’t do the digits justice, they look higher contrast in a normal room: Then I grabbed the MAX7219 8-digit LED module that recently arrived from eBay for $10.Ĭonnected together and assembled into a lunch box it looks like this: And then if the processor was run at around 3.3V then anything over around 1.65V would be HIGH, which was even better. Here are its pinouts:Ī lot of time was wasted trying to find suitable level-converters for it, since it outputs at 2.85V (at 4800 baud) until I realized that 2.85V would count as HIGH on a serial port, without needing a level converter. I had a EM-406a GPS module lying around, purchased for a day like this. (Just joking, but there are a lot, once you allow for clocks in ovens, microwaves, VCRs, etc.). Time is shown in hours and minutes since midnight.As daylight savings ends here (in Australia) this Sunday, I thought it would be a good time to make up a GPS clock I could take around with me as I reset the 1000 or so clocks we have here. The day runs from midnight to midnight and is divided into 24 hours from 0 (midnight) to 23. The abbreviations AM and PM are from Latin: The day is split into two 12 hour periods running from midnight to noon (AM hours), and noon to midnight (PM hours). The table below shows the conversion between the 12 hour and 24 hour clock systems: 12 hour clock In the 12 hour clock method, it is 12:00 twice a day at midnight (AM) and noon (PM). Most countries prefer the 24 hour clock method, but the 12 hour clock is widely used in Latin America and English-speaking countries. First there's the 12 hour clock that uses AM and PM, and then there's the 24 hour clock. There are two primary methods of showing the time.
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