LostLess
Member
@gbulmer: I see. Thank you for the clarification.
I tried connecting Vcc to the low voltage pin of the logic level converter...still nothing. I suspect something may be wrong with the data (SCLK, MOSI) connections on the LPD8806...I will double check those. Otherwise, everything seems intact. Just to make sure, do I have to enable that port in my code, or is Vcc already outputting 3.3V?
gbulmer
Moderator
LostLess - "Just to make sure, do I have to enable that port in my code, or is Vcc already outputting 3.3V?"
If the Maple Mini is being powered then Vcc is providing 3.3V.
Vcc isn't connected to a port, but directly to a voltage regulator. Have you got a multimeter or something to double-check the voltage? You could wire an LED and current-limiting resistor across Vcc to ensure it's easy to see that something is happening.
I notice your pastebin code uses SPI at 18MHz, which is pretty quick.
I would be tempted to use simple bit-banging to drive the LED strip.
Use two ordinary pins and digitalWrite, to drive the clock and data.
Have you had the LEDs working at all?
Have you got an Arduino, so that you could use Adafruits code https://github.com/adafruit/LPD8806
I'd suggest dropping the SPI speed to SPI_281_250KHZ as you might be able to see if there is any changes!
Bit banging is also possible. From what I can see, with a few minor adjustments, you could actually use the library. I'd also try to simplify your code, just attempt to get a single colour written to the strip. Something like this:
http://www.crennsmind.com/Code/Maple/LEDstriptest.pde
LostLess
Member
Have you got a multimeter or something to double-check the voltage? You could wire an LED and current-limiting resistor across Vcc to ensure it's easy to see that something is happening.
Yes, I have a multimeter and I have verified that Vcc out is working (it is outputting around 3.6V, but that's ok...I don't expect it to be exact).
I notice your pastebin code uses SPI at 18MHz, which is pretty quick.
I would be tempted to use simple bit-banging to drive the LED strip.
Use two ordinary pins and digitalWrite, to drive the clock and data.Have you had the LEDs working at all?
I can try to slow down the speed, but I am not sure if it will make much difference. The LEDs do work, but only when the Maple Mini is connected to the PC. I don't have an Arduino unfortunately...
@crenn:I will try to drop the frequency down to the suggested frequency of SPI_281_250KHZ. I just find it strange that at 18Mhz, when the Maple Mini is connected to the PC, everything works fine. If that does not work, I will try the bit banging code you suggested.
gbulmer
Moderator
LostLess - The datasheet I eventually found (from Greeled Electronics) says the maximum speed for the LPD8806 clock/data signals is 20 MHz, but recommends 0~2 MHz, so speed might matter.
Also if it works with one power supply, yet not another, it might be close to an edge of some sort, so it is worth backing-off.
"... I have verified that Vcc out is working (it is outputting around 3.6V, but that's ok...I don't expect it to be exact)."
I wouldn't expect Vcc to be exactly 3.3V, but 3.6V is high for Vcc (the STM32F maximum operating voltage range is 2V to 3.6V). Also AFAIK the voltage regulators are usually within 100mV (or better) when operating within their spec, so 3.6V seems odd. Can you disconnect everything from the Maple Mini and check the voltage on Vcc again?
LostLess
Member
crenn, your code works! It even works with my 4.8V battery! I don't even need the logic level converter...it works fine without it!
So, it looks like the hardware situation is fine now. What I don't understand is why the code involving the opening of the serial port @ 115200 bps for the bluetooth modem causes a problem (by the way, the modem is still plugged in, so its power draw can't be an issue as far as I can see).
What I am going to do now is try to add in the serial port code into yours to make a modified version and see what happens from there.
The best solution I feel would be to port the library to allow easier coding for you. I'm not promising anything, but I'll take a look into it.
The problems I feel your code was having is it wasn't doing the right number of latches, and all colours need to be ORed with 0x80 to ensure the LEDs received the appropriate data.
Just finished porting the library, since I don't have the hardware to test, I can only confirm that the code compiles. Let me know if you have any problems with the library.
LostLess
Member
That's very kind of you crenn...thanks again! I will try out the ported library. I think I can take it from here. After trying out the library, I am going to look at re-integrating the serial port code so I can use bluetooth. If there are any problems from here, I will start a new thread, as the problem is no longer identified with hardware.
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