So, I would replace the 32K eeprom with 64k eeprom;
3x 100nF ceramic caps
3x 33uF electrolytic caps
1x 64kx8 EEPROM
1x 5Mhz crystal
1x L1117-3.3v voltage regulator (assuming you will power from ~5V)
add a 5v regulator;
1x L1xxx-5v voltage regulator (to power from external battery etc)
And maybe a switch to ensure USB power and external battery are not connected at the same time.
1x 40pin dip socket
1x 8pin dip socket
1x strip/proto board
... and remove the propplug and use the FTDI chip directly. Instead of a mini USB, maybe we could hack the end off surplus USB cable and wire it directly.
While the one-off price would be higher than $4 (I'll check the exact numbers next), I'm thinking it could still be less than the $30 for a quickstart or $24 for a mini.
The bulk has been about half of the on-off price. Since its a kit, it could be doable.
Not that my eyes could do much for hand soldering on to surface mount parts, I'm just looking at the prices for now.
Of course it does not use a crystal, limiting the speed... and using a crystal on a breadboard may not be very precise (due to the extra capacitance of the long bus bars)
The Propeller Simple Spin Board is more minimal than Bill Henning's good list. It should be easy for students to assemble in about 5 minutes. The concept is to load and run programs from the prop's RAM using a host. It could use another prop and EEPROM to load a specific program, or you could add a preprogrammed EEPROM.
... and using a crystal on a breadboard may not be very precise (due to the extra capacitance of the long bus bars)
The extra capacitance from the layered bus bars (which form capacitors) may actually contribute more effectively to the decoupling capacitance requirements of the Propeller chip.
The extra capacitance from the layered bus bars (which form capacitors) may actually contribute more effectively to the decoupling capacitance requirements of the Propeller chip.
You're not gonna get anywhere near 0.1uF that way. You still need the bypass caps.
And yes, the stray capacitance will affect crystal loading and pull the frequency some -- but not by much.
Maybe, maybe not. I forgot to mention, the chip was on a solder-less breadboard. The bus strips act like capacitors. In the case of each side of the propeller chip, four sandwiched and equally spaced bus bars create a capacitor which may contribute to the chip's decoupling.
Edit: I was looking at the Wiki which states a single bus strip can have capacitance ranging from 2 to 25 pf per contact point. There are four sandwiched layers of bus bars on each side of the prop chip on the solder-less breadboard making a larger capacitor. I won't know how close this is to the recommended 100 nf until measuring it.
See my comment above. 0.1 uF = 100,000 pF. You won't get that from contact strips. BTW, one of the Propeller's known failure modes (bricked PLL) is associated with inadequate bypassing. -Phil
You are right. Somehow I changed PF to NF in my mind! Lack of sleep I guess. My bad.
I ordered 3 PCB, this product should be mass produced to get cost down,
Prop $5 + PCB $6 + breadboard $3 + LEDs (built in resistors) $1 = $15 cost (sell for $19)
Comments
L1117-5.0 is the 5V version.
Of course it does not use a crystal, limiting the speed... and using a crystal on a breadboard may not be very precise (due to the extra capacitance of the long bus bars)
The extra capacitance from the layered bus bars (which form capacitors) may actually contribute more effectively to the decoupling capacitance requirements of the Propeller chip.
Source
And yes, the stray capacitance will affect crystal loading and pull the frequency some -- but not by much.
There's a way around that: http://forums.parallax.com/showthread.php/148997
-Phil
have a prop chip running off and on for a couple years without the bypass capacitors. Pure luck?
Maybe, maybe not. I forgot to mention, the chip was on a solder-less breadboard. The bus strips act like capacitors. In the case of each side of the propeller chip, four sandwiched and equally spaced bus bars create a capacitor which may contribute to the chip's decoupling.
Sources
Edit: I was looking at the Wiki which states a single bus strip can have capacitance ranging from 2 to 25 pf per contact point. There are four sandwiched layers of bus bars on each side of the prop chip on the solder-less breadboard making a larger capacitor. I won't know how close this is to the recommended 100 nf until measuring it.
BTW, one of the Propeller's known failure modes (bricked PLL) is associated with inadequate bypassing.
-Phil
You are right. Somehow I changed PF to NF in my mind! Lack of sleep I guess. My bad.
Prop $5 + PCB $6 + breadboard $3 + LEDs (built in resistors) $1 = $15 cost (sell for $19)