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Forum Index : Microcontroller and PC projects : Silicon Chip picomiteVGA works but can't access SD card
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| frewie Newbie  Joined: 28/07/2022 Location: AustraliaPosts: 3 |
Just completed kit construction of the VGA Picomite (Design #1) by Geoff Graham published by Silicon Chip magazine in Australia. Kit worked from first power up but can't access SD card/reader. Have resoldered connections and tested various aspects, but no progress. See below: Saved 45 bytes 5.0704 PicoMiteVGA Not present 126000000 > list Print MM.Ver Print MM.Device$ Print MM.Info(sdcard) Print MM.Info(cpuspeed) > > option list OPTION COLOURCODE ON OPTION KEYBOARD US OPTION SDCARD GP13, GP10, GP11, GP12 > Any suggestions for what I could try? I can save programs to flash memory, but SD card gives greater flexibility, storage and exchange with other computers. Hope someone can help me - cheers Peter |
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| JohnS Guru  Joined: 18/11/2011 Location: United KingdomPosts: 4147 |
What tools ('scope etc) do you have to look at signals? John |
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Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3308 |
You seem to have the SD card configured correctly and because the interface is so simple there is not much left to go wrong. I would suggest: - Make sure the SD card is 32GB or less and formatted FAT32. - Try a few different SD cards, I have had a few that just did not work. - Is the SD card soldered flat to the PCB? This ensures that the card will mate with the connector's contacts. - Recheck soldering. Are all 16 pins soldered with no bridges (check each one). Geoff Geoff Graham - http://geoffg.net |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8304 |
First, your SD card has to be 32GB or smaller and formatted to FAT16 or FAT32. Windows 10 will want to format it to exfat by default and that format isn't recognised by the PicoMite. You may need to use a utility such as Rufus to get the correct format. Onto the hardware... Have you got a test meter of some sort, Peter? Even an LED, resistor & battery would do - you are only doing simple tests first. You'll need to refer to the schematic. With the PicoMite unplugged, check for shorts between pairs of adjacent pins from 13 to 19. Also test for continuity between pins 14-17 and the SD card socket. Still with the PicoMite unplugged, power up and check for 3.3V at the SDcard socket pins. There have been instances in the past when some SD cards simply won't work or are unreliable. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2832 |
Adding to Geoff's suggestions use a multimeter to check for continuity from the SD socket pins to the Pico pins and to 3.3V and both ground pins. Check that you don't have continuity between any adjacent pins. There have been suggestions that increasing the 100nF cap. near the socket to 10uF helps, though I haven't seen any difference. |
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| frewie Newbie Joined: 28/07/2022 Location: AustraliaPosts: 3 |
Hi Geoff, success. I used solder wick on the terminals of the SD card reader and resoldered them and it is working now. I had already resoldered them unsuccessfully, but the solder wick did the trick. Thanks a lot. Peter |
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| frewie Newbie Joined: 28/07/2022 Location: AustraliaPosts: 3 |
Thanks also to phil99 - had checked with multimeter for continuity and all okay, must have been a dry joint, which came good with heat and solder wick. Also thanks to Mixtel90 for your suggestions. Great community support to help me fix the problem. |
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