DM-15CC - a real HP 15C clone
dm15cc.jpg


Front view and its font

Smooth font
Firmware = DM15CC_MEM80_V8
Slim font
Firmware = DM15CC_S_V10
dm15cc-front.jpg dm15cc slim font

Internal view

dm15cc-mpu.jpg
(NXP LPC1115F/303 12MHz, SILABS CP2012DCL0Y5, C6=100uF)

Note *1 : There is a possibility of bare short circuit of the battery, caused by accidental contact of the outer terminal of the battery holder to the ground through the housing and the shield of the mini-USB inlet. It's recommended to use some insulation material such as Kapton(R) tapes between the battery holder and the housing.
Note *2 : The housing of the calculator is not electrically connected to the PCB. It's recommended to connect the housing to the ground of the PCB to prevent ESD and EMI problems.
Note *3 : It seems to correct dust easily by electro-static because both the keypad overlay and the paint of the housing are not treated nor made of anti-static materials. To make the things worse, its physical shape work as a scraper to gather the dust into the calculator through the large clearance between the housing and its front pannel. It's recommended to use anti-static materials for the calculator body, and preferably to use dust seal or at least dust preventing structures.

Current draw

Power off state (sleep) current Isleep ≤ 1.8uA (Vdd = 3.00V, Ta = 25C)

Test circuit (DUT = DM-15CC, firmware = DM15CC_MEM1B_V10)
Test circuit DM-15CC under test

Note *4 : Vdd of 3.00V is shown as 2.815V in the information displayed by [ON]+[E]


Standby current (Vdd = 3.00V, Ta = 25C)
mode = 12MHz ( 5mV/div ≡ 1mA/div) mode = 48MHz ( 5mV/div ≡ 1mA/div)
Istandby@12MHz Istandby@48MHz

Note *5 : There seems to be a problem in standby state of 12MHz mode. Its average standby current is much higher than that of 48MHz mode.

Operating current *6(Vdd = 3.00V, Ta = 25C)
mode = 12MHz ( 5mV/div ≡ 1mA/div) mode = 48MHz (20mV/div ≡ 4mA/div)
Irunning@12MHz Irunning@48MHz

Note *6 : while executing self test invoked by pressing [ON] and [×].

Key combinations

keysfunctiondescription
[ON]+[B]benchmarkevaluate benchmark compared with orig. calc
[ON]+[C]serial consoleswitch to serial console (38400, 8N1, without flow control)
[ON]+[E]show informationfirmware version & battery voltage
[ON]+[CHS]LCD settingschange LCD contrast
[ON]+[7]change fonttoggle from 7segment to smooth font and back again
[ON]+[9]change speedtoggle from 12MHz to 48MHz and back again
[ON]+[/]key testsame as on the original calculator
[ON]+[*]self testsame as on the original calculator
[ON]+[-]power resetsame as on the original calculator
[ON]+[+]same as on the original calculator
[ON]+[.]toggle . and ,same as on the original calculator

Serial console (38400bps, 8bit, parity none, 1 stop bit, no flow control)

serial console command help

VOYAGER >> ?
Firmware DM15CC_MEM1B_V10

?          Help
p          Key press
s          Dump memory
l          Load memory
t          Toggle display output to console
b          Read battery voltage

Type '<command> ?' for params
Uptime 72s
VOYAGER >> 

Benchmark result

N-queen benchmark : 3m16s (DM15CC MEM1B V9 48MHz), x = 876, y = 8

Memory dump (calculator model = DM15CC_MEM1B V14)

example1 - N-queen benchmark

example2 - Electrical Engineering library
Programs in the Engineering library
Entry
point
functioninputoutput
ASynthesize
Microstripline

Z→w
X = Zmicrostrip
R7 = εr
R8 = height
R9 = thickness
X = width

Y = 1/√εreff
BAnalyze
Microstripline

w→Z
X = width
R7 = εr
R8 = height
R9 = thickness
X = Zmicrostrip
Y = 1/√εreff
CRational
interpolation
X = xi
R1 = x1, R2 = x2, R3 = x3
R4 = y1, R5 = y2, R6 = y3
X = yi
DDifferential
Impedance
s→Zdiff
X = side gap
R0 = Z
R8 = height
X = Zdiff
EfactorX = positive integerE = factors
1Z→S11X = R + jXX = S11
Y = Return loss
Z = VSWR
2LCM
GCD
X = positive integer
Y = positive integer
X = LCM
Y = GCD
3Fractional
approximation
X = decimal numberX = denominator
Y = numerator

APPENDIX - Program library

SEE ALSO


EXTERNAL LINKS

DM swiss made calculators
The Museum of HP Calculators
Flash Magic Tool
Silicon labs, CP210x USB to UART Bridge VCP Drivers

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