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Forum Index : PCB Manufacturing : small 100pin pic32mx board sn-5x
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| isochronic Guru  Joined: 21/01/2012 Location: AustraliaPosts: 689 |
I have had a go at designing a small 100 pin pic32mx board. ( sn-5x ) It is 2 x 3 inches (50 x 75 mm), and has the power supply, usb-serial bridge and direct usb connections. I assembled it with a pic32mx795L. The barrel connector for power and 6 pin ICSP/pickit3 plug show the scale. The IC pins are connected to the 4 25pin banks (apart from two pins ca. Vcap). So far (I have not tested the direct usb connect yet) it is going ok, polling a ds3234 rtc and running a f77 solar position calculation every second. it is the first time I soldered a 100 pin chip, and it survived that as well ! The intent is to go to a mx470 which shares the pinout. This has one usb and one 25pin bank in place on a purple pcb, (ed) the photo is a bit murky though. The pads and connections for the other usb socket are on the other side. 
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bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2916 |
Hi Chronic, That looks a pretty decent board. Is that an FTDI FT232RL chip bottom left? My only concern is there are so many fake versions of that chip floating around that you need to be careful that you get a good one. What do you intend to do with it? Kind Regards, Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| isochronic Guru Joined: 21/01/2012 Location: AustraliaPosts: 689 |
thanks, the serial bridge is a mcp2200 , I had a few from a long time ago so I used one ... I wanted a small board with all the ancilliary caps etc and the legacy serial and also direct usb. It is really a first step to using faster chips ... the aim is to run Colossal Cave (f77) on a MZ EF or better (sad! :)) ) It is a mental exercise for me, it is good to do something constructive instead of being stressed by the archipelagos of govt-paid quangos. It is basically a vanilla connection board, I will tweak it a little yet. Don't know if it will run the Colour MM to a console or not. Maybe I could flog a few, (ha) ! Makes me appreciate the UBW32 design a lot - amazing but a different aimpoint. |
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| isochronic Guru Joined: 21/01/2012 Location: AustraliaPosts: 689 |
I tried the Colour MMBasic interpreter on it, to test the USB connection, and it is running. So both the serial-legacy USB and native USB look ok. BUT What is the best way of connecting the IO fanout ? Dual-pin header sockets seem ok but groups of 25 are awkward.. Any 26-pin dual row plugs etc leave a pin dangling even if they can be sourced reasonably.. the single row 25pin connectors 20-per-inch are expensive.. ?? A good feature of the UBW32 etc is that the pin groups are sensibly bunched. The pic32mx 100pin port pin groups tend to be dispersed a bit and scattered. |
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| isochronic Guru Joined: 21/01/2012 Location: AustraliaPosts: 689 |
Connected up to the RTC, a small lcd and keypad with temporary cables etc, running solar position calculation once per second. Taken at dawn (just) in very dim midwinter light (in "shadow" of buildings, trees, clouds, etc) that the camera and browser do not handle well, sun approx. 0.7 degrees up but hidden. Azimuth 62.660 degrees from north changing to 62.662, Elevation 0.769 degrees from horizon. Plenty of connections still available but a bit congested. 
The RTC ( spi DS3234) has drifted approx. 7 seconds in 8 months, not bad at all. |
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| isochronic Guru Joined: 21/01/2012 Location: AustraliaPosts: 689 |
I have now tried this board with a (100 pin) pic32mx470L - looks like it is ok, at least it is programming with pickit3 without hassle. Now to alter the C to suit it 
The pinout is also shared by pic24 and dspic33 100 pin chips, so with a bit of luck maybe this will suffice as a sub-explorer16, as a cheap intro base. |
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| isochronic Guru Joined: 21/01/2012 Location: AustraliaPosts: 689 |
Eeeeha!.. Screenshot .. with a default format of nine decimal places...count 'em.... 
ELECTRIDE 2.0 © S. Oliver 2014, 2015, 2016
with content ©Microchip and ©GCC Trial PIC32MX470L versionX (G) Get (L) List (S) Save (A) Analyse (R) Run (C) Comp (res) >R PROGRAM double C DOUBLE a a = 1.123456789 PRINT *, "a = ", a END \ a = 1.123456789 But, I am wondering, it might be better to work on the MZ's now, as they have a better outlook. (?) |
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| isochronic Guru Joined: 21/01/2012 Location: AustraliaPosts: 689 |
OK the board is at the developed stage, now named Komodo as per lizard. The pins are in the same sequence as the processor for convenience. The fundamental layout is the sn-5x pcb above, slightly modified to keep it sensible, and trial usb2go wiring as well. My own software Electride runs well, I also got the Colour MM MMBasic prompt so I guess it could also be used (BYO peripherals). Trialled with a pic32mx795l (14x14mm), the processor, power supply, icsp, usb-serial and intrinsic usb connections are all working nicely, so a pic32mx470 should also be ok. I haven't tried the usb2go wiring yet. By design, some of the chip power supply pins are not brought out to the peripheral connectors, as the idea is that other ancilliary boards should have their own power connections, which also keeps the processor power cleaner. I will have a batch to distribute soon but am clobbered with work so it will have to be on the back-burner for a bit. |
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| isochronic Guru Joined: 21/01/2012 Location: AustraliaPosts: 689 |
Further trialled with pic32mx470L to test that the direct USB cient wiring was ok. Fitted it with 20 Mhz crystal and loaded Micromite Plus hex file no worries, was rewarded with the chevron prompt  So it should be OK for experimenting and development purposes, apart from using two pins for its own serial bridge. Current approx 100 mA which is ok. Pros : The IC pins ( ie the 100, apart from 4 power pins ) are brought out to the connectors, so it is good for ratnesting. Runs ok at 12 v, eg a old portable drill battery works well. A few pcb frreebies are still available Cons: The heatsinking is pretty ordinary at 12v but should be ok, maybe fit a copper flag of some sort for extended hot climates, especially if a '795 is used instead. A power spike clipper would be good. Not as fast as an MZ.. (finaled as mod a, so moved to mod - a topic in mcu thread ) |
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