Brad Robinson

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About Brad Robinson

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  1. Recording from Delta-Sigma DAC to PC

    Hey All, I'm trying to record audio from classic computing shield (which I think is basically the same as the arcade shield) but just getting terrible noise. The sound works fine when plugged into powered speakers, but plugging to sound card on my pc and recording/monitoring just gives buzzing/hissing noise. I've tried both mic in and line in on the sound card, same result. I'm guessing this is because of the way this kind of dac works, but wondering if there's some other reason. Has anyone else managed to get a clean recording into a PC from one of these shields? What am I missing? Brad
  2. Reset behaviour question

    Thanks Alvie... I've got something working well enough for now but I think I'll need to revisit it - sometime manual reset through the classic shield reset button doesn't work quite right. I guess because of the multiple clock domains. Brad
  3. Reset behaviour question

    OK, so I figured this out... silly amateur mistake on my part. For the record, the problem was caused by using synchronous resets and also connecting the reset signal to the coregen'd clock core. This of course caused the clock core to stop and therefore parts of the design weren't getting the reset (synchronous reset won't reset without running clock). Interestingly the slower clock circuits were getting reset while the faster ones weren't. Anyway, lesson learned.
  4. Reset behaviour question

    Hey All, I've got a problem with a design I'm working on for Papilio Duo as follows: Programming SPI flash works fine and starts up correctly on every power on. After power on if I program the FPGA directly there's some randomness in whether it starts correctly. Usually it fails. Basically the Z80 code executes in a way that can "never happen". Either the T80 core isn't getting reset correctly or there's some issues with ram/rom. It looks like a CALL instruction is simply skipped. After programing to FPGA, using the reset button on the classic computing shield resets correctly - everytime. So... I'm wondering if there's something different about the reset procedure after programming directly to FPGA vs programming to SPI Flash using the reset button. I'm sure this is an issue in my design, but not really sure what to look for - any hints greatly appreciated. Brad
  5. Issues reading SD Card on Classic Computing Shield

    Follow up... I finally figured it out. It was a combination of block number miscalculations and some timing errors in my design. The SD slot on classic computing shield works fine with both SD and SDHC cards (at least the ones I have). Thanks for the help.
  6. Hey all, Anyone know how much current I can safely draw from the 3.3 and 5V supplies on the Duo board. Looking to power 1x MAX7219 based 8x8 matrix module. Says max current draw is 2A, but I'm only going to be lighting a few leds and can dial down the brightness. Brad
  7. Issues reading SD Card on Classic Computing Shield

    Thanks! I'll look into some of these options. In the meantime I haven't had much time to play with it, but I've tried 3 or 4 other cards now and still no luck. I'll post back when I figure it out.
  8. Hi All, First post here... I'm in the process of porting my FPGA 80's home computer to Papilio Duo but currently stumped by the SD card. I'm using a Papilio Duo and a Classic Computing Shield. What I'm seeing is exactly like what's described in this post - http://electronics.stackexchange.com/questions/106667/microsd-card-wont-return-any-data-on-read-command. Basically the card initializes correctly as SDHC, a read command is issued, the read response returns success, the lead token on the data packet comes back as expected, but the data is all zeros. I've double checked the data on the card multiple times and it definitely contains data. The cause of the problem in the above post was related to voltage drops once the read starts. ie: the card initialization and most register related commands worked but any access to the actual memory resulted in zero data due to a 2v drop. So... I'm wondering if this might be a problem with the way I'm powering the board or with the shield itself. I'm powering it via USB port from my Macbook but have also tried USB plugged straight into a iPhone charger. Anyone else seen issues like this? Any help resolving this would be much appreciated including suggestions of other projects/designs that are known to work that I could use for testing the hardware side of things. Brad btw: here's the details on my project - http://fpgabee.toptensoftware.com - it's an FPGA emulation of a Microbee which was an 80's home computer designed and built here in Australia.