There is no reply from the supplier (in Germany), nor any hit from my searches. The module has a simple RS232 connection which allows interrogation of the module to get 'atomic' date&time info, but details of the protocol are nowere to be found. I need the protocol documentation. https://www.hkw-shop.de/out/media/FMD01031R_FUM_DCF-U_DD.pdf
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The supplier now provided this information:
Data Exchange of Radio Controlled Clocks (RC Clocks) equipped with a PC serial interface
- Introduction
The serial interface consists of one data input line and one data output line. The data traffic speed of the serial interface is 300 bps. Because of the limited resources of the RC Clock micro-controller only an easy software protocol can be used. There are no hand shake lines. Synchronising to the host is by means of the character echo.
- Voltage supply of the serial interface
The RC Clocks with serial interface are battery operated radio controlled clocks which are powered by two 1.5V cells. This ensures a battery life of approximately two years. The voltage supply of the serial interface is independent of these batteries. The RS232 serial standard interface consists not only of the serial input (RxD) and output (TxD) lines but also some additional lines which are used in some applications for handshaking purposes, the RC Clock uses these additional lines to supply its internal serial interface circuit with the required electrical voltage. These additional lines are not needed for data exchange. The RC Clock requires both a positive and a negative voltage out of the PC's serial interface.
The positive voltage is supplied by the DTR line.
There are two ways of providing the negative voltage:
a) The PC "communicates" with the RC Clock by sending ASCII characters to the RC Clock as described below (see 5.). This allows the negative voltage to be provided by the TxD line. When the PC sends characters this line is toggled between a positive and negative voltage level. If the PC is waiting for the RC Clock to reply the TxD line is always low at a negative voltage. The RC Clock does not need the TxD negative voltage while receiving characters only while sending.
b) The RC Clock can be triggered to transmit the time/date information by pulling the data input line to high voltage level as described below (see 3.3). This line must be held high until the data transmission out of the RC Clock has begun. Therefore it cannot supply the negative voltage. The possibility exists to supply the negative voltage out of the RTS line. This line must be set to low level by the programmer who wants to cause the RC Clock to transmit the time/date information by holding TxD at high voltage level.
- Data word format
3.1. Data transmitted to the RC Clock
3.1.1. Interface parameters
a) MSF Version Speed: 300 bps Data Bit Count: 7 Parity: even, odd, mark, space (not checked by the RC Clock) Stop Bit Count: 2
b) DCF77 Version Speed: 300 bps Data Bit Count: 8 Parity: none Stop Bit Count: 2
3.1.2. Function of data input
The RC Clock accepts commands of up to three characters, including its parameters. The character carriage return (hex 0d) causes the RC Clock to execute the command. Only the four lower bits of each command and parameter character are used. For instance the characters "?", "O" and "o" have the same effect. The exception is the final carriage return which is completely decoded by considering the seven lower bits (MSF version) resp. all of the eight bits (DCF77 version).
3.2. Replies of the RC Clock
3.2.1. Interface parameters
Speed: 300 bps
Data Bit Count: 7
Parity Bit: even
Stop Bit Count: 2
3.2.2. Function of data output
The reply of the RC Clock consists of a sequence of ASCII characters terminated by a final carriage return character . The character set used by the RC Clock is limited to the numbers 0 ... 9 and the characters : ; < = > ?. The information is contained within the four lower bits. The bits 4 and 5 of every reply character are binary ones, the bit 6 is binary zero and the bit 7 contains the even parity bit. This results in the sixteen different characters transmitted by the RC Clock, as described above. The serial output of the RC Clock can not be interrupted during its reply. Therefore all characters must be taken by the host computer immediately.
3.3. Support of a simplified data exchange
A simplified data exchange is possible. The time/date information transmit command (( o ) see below 5.1.) is not the only way to initiate a sequence of ASCII characters. A simpler method is to pull the TxD (TxD of the PC) voltage level high. Normally TxD voltage level is low (inactive). If the TxD line is high at the start of a second then the RC Clock will transmit its time/date information. This can takes up to one second because the first start bit of the time/date information sets the beginning of a second. If the TxD line is held high continually then the RC Clock will transmit the time date information every second. But care must be taken: The current consumption of the RC Clock increases during the time/date information output (duration approximately. 600 ms) up to 200 ÊA.
- Handshaking
Every character received by the RC Clock is echoed. The next character must not be transmitted to the RC Clock before the echo of the preceding character and an additional duration of 10 ms. Recognising input characters is by checking the correct appearance both of the start bit and the two stop bits. The eight echoed data bits remain unchanged under all circumstances, regardless whether or not parity is even or odd.
- Description of commands
The commands 5.7. to 5.11. (set and read alarm times) are related to desktop alarm-clocks.
5.1. Transmit time/date information local time
syntax ASCII: o
Character "o" may be replaced if necessary by a character whose code contains the lowest four bits f(hex), e.g. also / ? O _
syntax binary: xxxx1111 00001101
The RC Clock replies to this command with a sequence of 15 characters which contain the complete time information and a final . Making 16 characters in total. The RC Clock will not reply immediately to this command because the start bit edge of the first reply character marks the beginning of the second. So the RC Clock will reply to this command at the start of the next second.
The characters have the following meaning: 1. hours tens 2. hours units 3. minutes tens 4. minutes units 5. seconds tens 6. seconds units 7. day of week 1 (Monday) ... 7 (Sunday) 8. day of month tens 9. day of month units 10. month tens 11. month units 12. year tens 13. year units 14. summer/winter status bit7 parity bit6 always 0 bit5 always 1 bit4 always 1 bit3 always 0 bit2 =1 if standard time is in effect bit1 =1 if summer time is in effect bit0 summer/winter time change impending bit =1 in case of change impending 15. status bit7 parity bit6 always 0 bit5 always 1 bit4 always 1 bit3 =1 if low battery voltage is detected bit2 MSF Version : don't care DCF77 Version: =1 if the first reception attempt failed and still no valid time information exists (bit0 = 0) The first succsessful reception attempt resets this bit. bit1 =1 if the latest reception attempt was successful =0 if the latest reception attempt was not successful bit0 =1 if the RC Clock contains a valid time information This bit is zero after reset and one after the first successful reception attempt.
5.2. Transmit time/date information UTC
syntax ASCII: u
Character "e" may be replaced if necessary by a character whose code contains the lowest four bits 5(hex), e.g. also e E
syntax binary: xxxx0101 00001101
The RC Clock replies to this command with a sequence of 15 characters which contain the complete UTC time information and a final . Making 16 characters in total. The RC Clock will not reply immediately to this command because the start bit edge of the first reply character marks the beginning of the second. So the RC Clock will reply to this command at the start of the next second.
The characters have the following meaning: 1. hours tens 2. hours units 3. minutes tens 4. minutes units 5. seconds tens 6. seconds units 7. day of week 1 (Monday) ... 7 (Sunday) 8. day of month tens 9. day of month units 10. month tens 11. month units 12. year tens 13. year units 14. BST/UTC status bit7 parity bit6 always 0 bit5 always 1 bit4 always 1 bit3 always 0 bit2 =1 if standard time is in effect bit1 =1 if summer time is in effect bit0 summer/winter time change impending bit =1 in case of change impending 15. status bit7 parity bit6 always 0 bit5 always 1 bit4 always 1 bit3 =1 if low battery voltage is detected bit2 MSF Version : don't care DCF77 Version: =1 if the first reception attempt failed and still no valid time information exists (bit0 = 0) The first succsessful reception attempt resets this bit. bit1 =1 if the latest reception attempt was successful =0 if the latest reception attempt was not successful bit0 =1 if the RC Clock contains a valid time information This bit is zero after reset and one after the first successful reception attempt.
5.3. Transmit clock status
syntax ASCII: f
Character "f" may be replaced by a character whose code contains the lowest four bits 6, e.g. also 6 F V v
syntax binary: xxxx0110 00001101
The reply to this command consists of four characters and the final . The characters have the following meaning:
1. tens of the count of hours since the latest successful signal pick up
2. ones of the count of hours since the latest successful signal pick up
3. status informations
bit7 parity
bit6 always 0
bit5 always 1
bit4 always 1
bit3 =1 for DCF77 version
=0 for MSF version
bit2 don't care
bit1 don't care
bit0 switching status,
alarm time 1 switches to 1
alarm time 2 switches to 0
4. ASCII "0"
5.4. Transmit reception status
syntax ASCII: g
Character "g" may be replaced by a character whose code contains the lowest four bits 7, e.g. also ' 7 G W w
syntax binary: xxxx0111 00001101
The reply to this command consists of two characters and the final . The characters have the following meaning: 1. Status of reception bit7 parity bit6 always 0 bit5 always 1 bit4 always 1 bit3 always 0 bit2 always 0 bit1 always 1 bit0 =0 if no reception attempt takes place at the moment =1 if a reception attempt takes place at the moment 2. reception quality characterising number from 0 to 5 5 indicates a good reception without any disturbances 0 indicates very poor reception conditions If the number is in the range from 0 to 2 no successful reception is to be expected normally. During reception pauses this number is always 0.
5.5. Start reception attempt
syntax ASCII: h
Character "h" may be replaced by any other character whose code contains the lowest four bits 8, e.g. also ( 8 H X x
syntax binary: xxxx1000 00001101
This command causes the RC Clock to activate the receiver IC and to start a reception attempt. If this attempt ends unsuccessfully bit 1 of the 15th time/date information character will be reset (see 5.1. and 5.2). This bit is set after completing the reception attempt successfully.
5.6. Start reception attempt
syntax ASCII: i
Character "i" may be replaced by any other character whose code contains the lowest four bits 9, e.g. also ) 9 I Y y
syntax binary: xxxx1001 00001101
This command is for compatibility reasons and does the same like "h" (see 5.5).
5.7. Transmit alarm times
syntax ASCII: j
Character "j" may be replaced by a character whose code contains the lowest four bits a(hex), e.g. also * : J Z z
syntax binary: xxxx1010 00001101
The RC Clock replies to this command with a sequence of 8 characters which contain both alarm times and a final . Time 1 corresponds to alarm time 1, time 2 corresponds to alarm time 2. The characters have the following meaning: 1. time 1, hours tens 2. time 1, hours units 3. time 1, minutes tens 4. time 1, minutes units 5. time 2, hours tens 6. time 2, hours units 7. time 2, minutes tens 8. time 2, minutes units
All characters contain the following bits: bit7 parity bit6 always 0 bit5 always 1 bit4 always 1 bit3 n3 bit2 n2 bit1 n1 bit0 n0
Bits n3...n0 contain the according numbers 0 ... 9 in BCD code. To deactivate one of the times bit 3 of the corresponding hours tens is to be set. Therfore the hours tens may contain not only 0, 1 or 2 but also 8, 9 and a(hex).
5.8. Set hours of alarm time 1
syntax ASCII: k
Character "k" may be replaced a character whose code contains the lowest four bits b(hex), e.g. also + ; K [
syntax binary: xxxxt3t2t1t0 xxxxu3u2u1u0 xxxx1011 00001101
This command causes the RC Clock to take over the two parameters which are the and into the hours register of alarm time 1. To deactivate alarm time 1 bit t3 is to be set. Attention: If parameters of this command are omitted the corresponding hours register will be undefined.
5.9. Set minutes of alarm time 1
syntax ASCII: l
Character "l" may be replaced by a character whose code contains the lowest four bits c(hex), e.g. also , < L \
syntax binary: xxxxt3t2t1t0 xxxxu3u2u1u0 xxxx1100 00001101
This command causes the RC Clock to take over the two parameters which are the and into the minutes register of alarm time 1. Attention: If parameters of this command are omitted the corresponding minutes register will be undefined.
5.10. Set hours of alarm time 2
syntax ASCII: m
Character "m" may be replaced by a character whose code contains the lowest four bits d(hex), e.g. also - = M ]
syntax binary: xxxxt3t2t1t0 xxxxu3u2u1u0 xxxx1101 00001101
This command causes the RC Clock to take over the two parameters which are the and into the hours register of alarm time 2. To deactivate alarm time 2 bit t3 is to be set. Attention: If parameters of this command are omitted the corresponding hours register will be undefined.
5.11. Set minutes of alarm time 2
syntax ASCII: n
Character "n" may be replaced by a character whose code contains the lowest four bits e(hex), e.g. also . > N ^
syntax binary: xxxxt3t2t1t0 xxxxu3u2u1u0 xxxx1110 00001101
This command causes the RC Clock to take over the two parameters which are the and into the minutes register of alarm time 2. Attention: If parameters of this command are omitted the corresponding minutes register will be undefined.
- Testing of the interface
By means of a simple terminal program the function of the serial interface can be tested. Here are parameters for Windows Terminal which are analogous to other terminal programs: - 300 Baud data speed - 7 data bits - Parity "space" - 2 stop bits - Protocoll none
- Interface: depends on the chosen serial interface (e.g. Com1:)
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