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Forum Index : Microcontroller and PC projects : DS3231 woes.
| Author | Message | ||||
| Bowden_P Senior Member  Joined: 20/03/2019 Location: United KingdomPosts: 162 |
Hi everyone, I am trying to use the 1Hz output ("SQW") from a DS3231 RTC module. I have the module plugged into the sockets on an MM+ E100 board, and intend to trigger a 1Hz interrupt - using the SETPIN instruction for a +ve edge interrupt - on pin 50. ( My MM+ E100 is a V1D, running MMBasic v5.05.03.) Using MMBasic's I2C instructions :- PIN(66)=0 SETPIN 66,DOUT I2C OPEN 100,500 ' I2C 100KHz, timeout 500ms. I2C WRITE &B1101000,0,2,&H0E,&H00 ' I2C Write, Address D0 hex, Option 0, 2 Bytes, 0E and 00 Hex. I2C CLOSE ' I2C close. There is a burst of activity on the clock and data lines, but no required o/p. ( The read variable MM.I2C = 0, showing the Write to be successful? ) The code should address the chip's Control register 0E hex, writing all zeros, which should enable the Square wave o/p at 1Hz. I don't get the RTC's SQW pin to output, which is stuck HIGH. I have a 10KOhm pull-up on this open drain pin. The RTC module has 4.7KOhm pull-ups on SCL and SDA, and the MM+ E100 gets its time and date reliably at switch-on. I also have an AM2302 Humidity/Temp module and a BMP180 Pressure/Temp module on the I2C bus - both also read reliably. Please can anyone suggest what I might be missing here ? With regards, Paul. Nothing so constant as change. |
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TassyJim Guru  Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
This is code I used a while ago: ' rtc as pulse dim n, interval, config1 interval = 30 RTC GETREG &h0E, config1 'print bin$(config1,8) config1 = config1 and &b11100011 RTC SETREG &h0E, config1 setpin 9, dout pin(9) = 0 setpin 10, intl, tick, pullup do loop sub tick if n mod interval = 1 then pulse 9, 50 print "*" endif n = n + 1 end sub I am sending &b11100011 plus whatever was already set. This is different to your bits. RTC pulse out connected to pin 10 on the MM pin 9 on the MM used to output a pulse for the CRO to monitor. You may need to change the pins to suit the Exp100 Jim VK7JH MMedit |
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| Bowden_P Senior Member Joined: 20/03/2019 Location: United KingdomPosts: 162 |
Hi TassyJim, Many thanks for your code. I patched the GETREG/SETREG section into mine - but without success unfortunately. The commented PRINT bin$(config1,8) reports 00000000 - as expected from the spec. I have a GUI LED onscreen, which flashes via the interrupt call on pin 50. This works - as proved by shorting pin 50 to 0V. With regards, Paul. Nothing so constant as change. |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2642 |
Hi Bowden_P Here is what I got from a "fresh" RTC module. > rtc gettime :? time$ 11:45:03 > RTC GETREG &h0E, config1 : print bin$(config1,8) 00011100 > Put that value for config1 in the second half of TassyJim's code and see what happens. If the magic smoke doesn't escape let me know, I could use the 1 pps o/p too. |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
I can confirm that pin-50 on the E100 board, is directly connected to the RTC module SQW pin, so once you get the register bits set correctly, that pin should indeed be the pin getting pulsed, so you have the correct pin. Keep us posted. It's been a LONG time since I used the SQW output on one of those RTC modules, but I know I did used to use that feature, and would have just set address &h0E to zero with RTC SETREG &h0E, 0 - which simply sets all eight bits to zero, then it should enable the SQW output, but as I say - its been years since I played with the 1Hz output on those modules. Smoke makes things work. When the smoke gets out, it stops! |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2642 |
Yes of course, I'm as thick as two planks. Adding the numbers:- > ? bin$((&b00011100 and &b11100011),8) 00000000 > Tried it and now have 1Hz o/p. > RTC SETREG &h0E, 0 'for 1Hz SQW > |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
Does the RTC module have the square-wave pin actually wired? I have some modules that I have had to add a jumper to get the output. I don't have an Exp100 so not sure which module it normally uses. Jim VK7JH MMedit |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
YAY!  Well done, phil99.  @ Jim: THIS is the module that the E100 uses, less the right-angled pin-header. Smoke makes things work. When the smoke gets out, it stops! |
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| Bowden_P Senior Member Joined: 20/03/2019 Location: United KingdomPosts: 162 |
Hi everyone, Many thanks for all your replies. There's an ancient saying dating back to the dawn of electronics that "Things TEND to work better when they're plugged in.", and this is a related failure - full marks to TassyJim. I had checked continuity from the module SQW pin to the PIC, and indeed had my 'scope connected to the same module pin. I guess you have spotted my error now - not checking continuity right up to the chip's actual pin 3. It's not connected on this module! Patching in the connection has the 1Hz outputting now. Sad to say I bought 2 modules together some time back - they look remarkably similar, but the other as yet unused one DOES have the SQW connection! Just sod's law I guess, that I picked out the one I did. I'll play with the I2C or SETREG ways of addressing the DS3231, to see if they both work - hopefully they both do. Many thanks again for your interest and replies - I'm relieved it's now working, Paul. Nothing so constant as change. |
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| Bowden_P Senior Member Joined: 20/03/2019 Location: United KingdomPosts: 162 |
Hi everyone, I can confirm that either the GETREG/SETREG or I2C commands work for this module - as you would expect! It's just a bit more bother when reading, to use 4 x I2C commands than the single GETREG one! All the best, Paul. Nothing so constant as change. |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
The joys of eBay shopping! VK7JH MMedit |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2642 |
If you ever need to get back to 'Factory Fresh' here is the lot. > for N=&H00 to &H12 : rtc getreg N,M% : ? N,hex$(N,2),M%,hex$(M%,2),bin$(M%,8) :next Address DATA 0 00 48 30 00110000 1 01 57 39 00111001 2 02 16 10 00010000 3 03 4 04 00000100 4 04 33 21 00100001 5 05 4 04 00000100 6 06 33 21 00100001 7 07 0 00 00000000 8 08 253 FD 11111101 9 09 255 FF 11111111 10 0A 255 FF 11111111 11 0B 255 FF 11111111 12 0C 254 FE 11111110 13 0D 255 FF 11111111 14 0E 28 1C 00011100 <set this one to 0 for 1Hz 15 0F 139 8B 10001011 16 10 0 00 00000000 17 11 11 0B 00001011 18 12 64 40 01000000 |
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| Bowden_P Senior Member Joined: 20/03/2019 Location: United KingdomPosts: 162 |
Hi Phil99, Thanks for the listing and output. I have pasted it into a file, and am keeping it with the datasheet for future reference. This device is the first I2C bus one I have tried using own-written code with, so am pleased to have gotten over that "hurdle", albeit simple, although the cause of the problem wasn't with me at all!! The other devices on the bus are an AM2302 Humidity/Temp module and a BMP180 Pressure/Temp module, but for those two I "lifted" the code from other sources, so didn't learn too much from them. Quite some time back I looked at both SPI and I2C for a multi-micro assembler-coded project - up to some 30 micros could be catered for - and chose SPI as it appeared simpler than I2C. However, realizing that each micro might need its own CS line, I instead opted for an address-based comms scheme, and really ended up with a sort of "I2C-over-SPI" protocol! It was a good coding challenge! With regards, Paul. Nothing so constant as change. |
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