I've not done a lot today other than solder on the ws2812b leds. I ended up using low temperature Sn/Bi solder and still ended up slightly melting one of the LEDs with the hot air gun.
I decided to use WS2812b's as they only need 1 pin from the fpga for 8 LEDs. I quickly ran up memory mapped controller for the 8 leds each with 3x4 bits of colour.
It turns out the ones I have are painfully bright:
Even turning down the exposure to 1/2000s and iso of 50 I need to interpose a couple of index cards before it doesn't horribly overexpose on the phone camera!
This is with the LEDs only using the bottom quarter of their range (I roughly gamma correct the 0..15 values into a 0..63 range our of a possible 0..255)
Tomorrow I'm going to try adding some "extra" PWM whereby I clock out the wanted rgb colours, then pause for 1ms then clock out all black, pause for 10ms...I've no idea though what the pwm frequency is internally and whether this will beat with the 1ms window.
The LEDs aren't just a gimmick - I do frequently resort to LEDs for debugging, plus Hoglet's BeebFPGA firmware can show its boot status on LEDs which can be a big help.
D
I decided to use WS2812b's as they only need 1 pin from the fpga for 8 LEDs. I quickly ran up memory mapped controller for the 8 leds each with 3x4 bits of colour.
It turns out the ones I have are painfully bright:
Even turning down the exposure to 1/2000s and iso of 50 I need to interpose a couple of index cards before it doesn't horribly overexpose on the phone camera!
This is with the LEDs only using the bottom quarter of their range (I roughly gamma correct the 0..15 values into a 0..63 range our of a possible 0..255)
Tomorrow I'm going to try adding some "extra" PWM whereby I clock out the wanted rgb colours, then pause for 1ms then clock out all black, pause for 10ms...I've no idea though what the pwm frequency is internally and whether this will beat with the 1ms window.
The LEDs aren't just a gimmick - I do frequently resort to LEDs for debugging, plus Hoglet's BeebFPGA firmware can show its boot status on LEDs which can be a big help.
D
Statistics: Posted by dominicbeesley — Fri Jun 13, 2025 11:42 pm