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Forum Index : Microcontroller and PC projects : Altronics Colour Maximite - Mystery Cap
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Nick Guru  Joined: 09/06/2011 Location: AustraliaPosts: 512 |
My Altronics Colour Maximite kit arrived and I wasted no time in getting it built up. I'm very impressed with board, a black board, double sided (4 layer?). The case is nice, much like the version in the Silicon Chip magazine. But one word of warning... *** Mount the tiny SMD 10mf capacitor FIRST! *** In the kit is a small bag with a tiny SMD capacitor. It's tiny at only 1mm wide and 1.5mm long. Dead easy to lose if you drop it. There is no mention of this part in the instructions and I didn't even see it in the schematics. I could't even see where it fitted on the PCB. I assumed it was accidently put in the kit and ignored it. That is, until I finished building the kit and the unit didn't fire up. I did a good job of soldering, checked power voltages, everything looked fine. That's when I turned my attention back to the SMD. There is nothing about this comoponent in the instructions but I eventually found a spot where it's meant to go on the PCB. It's barely marked and very tiny. It's almost like an aftermath "mod" added in later in the PCB manufacturing. Now, unless your hands are steady and eyesight good, you will struggle mounting this. This is why I say, *mount this part FIRST* while you have plenty of space around it and nothing hindering your progress. I found this to be the hardest part to put in. I've never done SMD soldering before so it was challenge putting this on as the LAST part. I can see this part being a problem area that Altronics should address to make what is almost a perfect kit. For some, this may be the downfall of the kit, ruining the fine tracks at this location and blowing their hard earned cash out the door. Why not use a normal sized cap, just make the pads larger and allow the constructor to solder a conventional "human sized" component here? Lucky for me, I got it mounted fine in the end and my Maximite booted first pop after that. Nick |
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Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3165 |
Ah, all excellent points and I think that you will have to blame me for that. Firstly, it had to be an SMD capacitor. That particular capacitor (connected to Vcap on the PIC32) is critical to the smooth running of the PIC32 and has caused a lot of grief for constructors. Microchip originally specified it as 10uF tantalum or ceramic so in the original Maximite I used a 10uF tantalum. You might remember that it did not work for some constructors and there was a debate on this forum about adding extra capacitors (some wired to +3.3V) to get the PIC32 running. In the mini Maximite I tried a higher valued tantalum but the real solution is to use a ceramic as they have a much lower internal impedance. The trouble is that 10uF ceramics are only available in SMD packages - so that was why the Colour Maximite has an SMD capacitor. I should have made a bigger point on soldering that cap in the article but, because I assumed that the constructor had soldered the PIC32, I thought that the cap would be easy. The other point is, if Altronics soldered the PIC32 why did they not solder the 10uF cap? A few years ago I was leery of SMD components but I have no problems now, in fact I find them easy (http://geoffg.net/SurfaceMount.html). Obviously I need to keep in mind that SMD is still new to some. Your comments are interesting in another way. I am currently designing a GPS tracking device which will probably find its way into Silicon Chip and I have been debating the package to use for a low Rdson FET. The SMD version costs about 20 cents while a thru hole version (in a huge TO-220 package) costs $2.80. After your comments I think that I will design the board to suit either. It must have been a thrill when you got the Colour Maximite going and your logo came up on the screen. I hope that you enjoy colour and I bet that there will be a lot of people looking forward to MaxMan in colour and other stuff. Geoff Geoff Graham - http://geoffg.net |
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| Keith W. Senior Member  Joined: 09/10/2011 Location: AustraliaPosts: 118 |
I also have built the Altronics Colour Maximite. I was looking for the 10uf capacitor because of previous discussions about requiring a special cap but thought it missing, nearly threw out the tiny smd. My unit worked immediately and displayed colour and ran programs. Although I was able to update the MMBasic via USB I experienced trouble when attempting to use TeraTerm via USB. I discovered that I had only 4.51 volts from the USB connection post the supplied 1N5819 Schottky diode, 3.3 volt supply OK. I was using 2 (short) USB cables in series. Removing 1 cable lifted the supply a little and it then worked. Using a computer USB port that is mounted directly on the motherboard raises the voltage another 0.01 volts. During software update the power LED is turned off and the voltage rises by 0.01 Volts. With my original SM1 Maximite I originally achieved 4.57 volts and have no problems with the cables in series. My Gigabyte motherboard and computer supply are about 1 year old. Using a DC supply all works OK with the diode dropping 0.32 volts from the regulated 5 volts. Perhaps with some computers the Colour Maximite MAY be marginal for USB communications when powered from the USB only. The USB port and cable used seem a factor when powering the Colour Maximite. An interesting question for GeoffG is that I think it possible for USB devises to specify the current to be supplied to them. What is the case with the Maximite? Regardless of the above my Colour Maximite with MMBasic V4.1 is fantastic. Keith W. |
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| Nick Guru Joined: 09/06/2011 Location: AustraliaPosts: 512 |
Thanks Geoff. That clarifies the SMD cap mystery. I had a look at the original Silicon Chip article and there, on the board layout diagram, the cap is more visible due to the colour print on the page. Maybe Altech should distribute the kits with colour photocopies of the original magazine articles instead of monochrome? Luckily, I had bought the magazines but what if someone only buys the kit? I've waited long enough for my Colour Maximite. It's time to write some software!! Halo 5 for Maximite? (Tell him he's dreamin'!!) Nick |
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| Nick Guru Joined: 09/06/2011 Location: AustraliaPosts: 512 |
Found 1 problem with my newly built Altronics Maximite. The clock doesn't run. I set the time and date with Time$/Date$ and it did store this but everytime I turn on the Maximite, it still is set to that time. Could this be the crystal? Nick |
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| Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3165 |
Yes, the Maximite tells the host that it needs a maximum of 200mA. However I think that most hosts ignore that and give you the full 500mA anyway. The Colour Maximite should work with USB voltages as low as 4.3V. I don't know what it is with USB power but it has affected many people (it could be high speed spikes on the USB 5V). Moving to a plug pack nearly always fixes the issue. That is a strange one and I have not seen it. I guess that it could be the crystal but check your soldering around there first. Geoff Geoff Graham - http://geoffg.net |
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| Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3165 |
By the way Nick, try running the COPYRIGHT command. You are listed there. Geoff Geoff Graham - http://geoffg.net |
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Bill.b Senior Member Joined: 25/06/2011 Location: AustraliaPosts: 225 |
Hi Nick I have CGs colour maxi and I use Ian Quirk's i2ctime.bas to set the external clock. I have dad no problems with the time date since. Bill In the interests of the environment, this post has been constructed entirely from recycled electrons. |
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| Nick Guru Joined: 09/06/2011 Location: AustraliaPosts: 512 |
I can set the clock using TIME$= and it stores this setting. If I let the maximite run for awhile and periodically PRINT TIME$, I can see that the time is changing correctly. If I turn the Maximite off, wait a few seconds then turn it on again, the time shown is the original time that I originally set it to. I can set it to something else then this becomes the time the Maximite always boots to. Any ideas? |
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| Bill.b Senior Member Joined: 25/06/2011 Location: AustraliaPosts: 225 |
Hi Nick How is the battery on the RTC Bill In the interests of the environment, this post has been constructed entirely from recycled electrons. |
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| Nick Guru Joined: 09/06/2011 Location: AustraliaPosts: 512 |
Yep. Full battery and it definately holds the set time. Pull it out and it loses the time. |
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BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935 |
As Geoff has already said, check the solder work around the crystal and the two connections from the crystal to the RTC. Check for bad joints or solder bridges. |
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| isochronic Guru Joined: 21/01/2012 Location: AustraliaPosts: 689 |
If I remember it correctly, the ds1307 has to have a bit set in a particular register before it's oscillator/clock will run, ie it has to be initialized. Maybe try the i2ctime.bas mentioned above. |
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| Nick Guru Joined: 09/06/2011 Location: AustraliaPosts: 512 |
Ok. Where do I get this program for my Maximite? Hopefully, that's what it is. Nick |
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| Bill.b Senior Member Joined: 25/06/2011 Location: AustraliaPosts: 225 |
Hi Nick the file i2ctime.bas is in the library files on Geoffs website. Bill In the interests of the environment, this post has been constructed entirely from recycled electrons. |
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| Nick Guru Joined: 09/06/2011 Location: AustraliaPosts: 512 |
I checked my soldering for shorts or dry joints... all looked good. I ran the I2CTIME.BAS program... problem still remains. Maybe I got a bad crystal? Nick |
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| ajkw Senior Member Joined: 29/06/2011 Location: AustraliaPosts: 290 |
Nick, From what I have been led to believe the CMM only reads from the RTC on boot and can only be set with the TIME$ command. I do not believe the i2ctime program will be able to communicate with the RTC on PIC32 pins RA2 and RA3. If I am not mistaken the i2c commands will only try communicate with a device on Pins 12&13. Anthony. |
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| Bill.b Senior Member Joined: 25/06/2011 Location: AustraliaPosts: 225 |
[quote] From what I have been led to believe the CMM only reads from the RTC on boot and can only be set with the TIME$ command. I do not believe the i2ctime program will be able to communicate with the RTC on PIC32 pins RA2 and RA3. If I am not mistaken the i2c commands will only try communicate with a device on Pins 12&13.[/quote] I do not know if the CGCOLORMAXI is different from the Altronics colour maxi, but I ran I2CTime.bas to set the time and date. It has been displaying the correctly time and date ever since. Bill In the interests of the environment, this post has been constructed entirely from recycled electrons. |
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| ajkw Senior Member Joined: 29/06/2011 Location: AustraliaPosts: 290 |
Bill, Well that is interesting. I would have thought the CGCOLORMAXI has the RTC wired to the same pins as the CMM, I haven't been able to find a schematic of the CGCOLORMAXI to confirm. Anthony. |
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| paceman Guru Joined: 07/10/2011 Location: AustraliaPosts: 1326 |
Nick, Guessing a bit here but voltage might still be the problem - here's some extracts from the 1307 datasheet: DETAILED DESCRIPTION .....Access to the DS1307 is obtained by implementing a START condition and providing a device identification code followed by a register address. Subsequent registers can be accessed sequentially until a STOP condition is executed. When VCC falls below 1.25 x VBAT, the device terminates an access in progress and resets the device address counter. Inputs to the device will not be recognized at this time to prevent erroneous data from being written to the device from an out-of-tolerance system. When VCC falls below VBAT, the device switches into a low-current battery-backup mode. Upon power-up, the device switches from battery to VCC when VCC is greater than VBAT +0.2V and recognizes inputs when VCC is greater than 1.25 x VBAT. Pin 3 (Vbat) Min 2.0v Max 3.5v ....Battery voltage must be held between the minimum and maximum limits for proper operation. Diodes in series between the battery and the VBAT pin may prevent proper operation. If a backup supply is not required, VBAT must be grounded. The nominal power-fail trip point (VPF) voltage at which access to the RTC and user RAM is denied is set by the internal circuitry as 1.25 x VBAT nominal. A lithium battery with 48mAh or greater will back up the DS1307 for more than 10 years in the absence of power at +25°C. Pin 8 (Vcc) Min 4.5v Max 5.5v (Ground is Pin 4) Primary Power Supply. When voltage is applied within normal limits, the device is fully accessible and data can be written and read. When a backup supply is connected to the device and VCC is below VTP, read and writes are inhibited. However, the timekeeping function continues unaffected by the lower input voltage. It's very specific about when it allows read/writes, updates, etc. What is the Vcc supply voltage and the Vbat voltage you have at the chip? Also, when you removed the battery and put it back, was the board powered or not? If it was powered then the 1307 should have ignored that anyway. As I understand it, the RTC clock is only read once, immediately on power-up and then MMBasic keeps time from that - but it does somehow know if the RTC isn't running on power-up because it comes up with the "Clock Not Set" message under the logo to remind you to issue a Time/Date command. I assume that subsequent to that, if a new Time/Date MMBasic command is issued then it would also be written to the RTC, not just MMBasic. Anyone else with some comments on this? Greg |
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