eDrum - FAQ

Frequently Asked Questions

Q. It doesn't work! HELP!
A. Try this:
1. Check voltage on PIC pins 11 and 32: must be +5v
2. Check voltage on PIC pins 12 and 31: must be 0v
3. Check voltage on pin 1: must be +5v
4. Check LCD cabling, then check it again. This is by far the most common failure!
5. Check that connection exists between GND and AGND.
6. You don't need MAX232 at all, you can leave it out.
7. If the MIDI LED doesn't blink on startup, check crystal and try to flash PIC again.
8. Check PIC EEPROM values.

Q. Aren't 100nF same thing as 0.1uF?
A. 100nF = 0.1uF

Q. What is the b40c500? Please give me more info.
A. b40c500 is a standard bridge rectifier (4 diodes). Use any equivalent, b40 means 40 Volts max, c500 means it supports up to 500mA.

Q. What is the '10k lin'?
A. '10k lin' is a 10k linear potentiometer.

Q. What is the '20MHz X1'?
A. 20MHz X1 is a crystal with frequency of 20MHz.

Q. Resistors marked as 100, 220 etc, are these means Ohms?
A. All resistors with values without suffix letter are in ohms and capacitors are in pF, this is kinda "default" in electronics.

Q. What programmer should I use to flash my PIC. Could someone advise me?
A. I'm using this one:

Q. What is the most simple way to built e-drum?
A. The most simple way to build eDrum is using eDrum24 PCB.

Q. Firmware is the same for all PCBs in the site?
A. No. There are 3 different firmwares: 16, 22 and 24 channels

Q. How hard is it to make this (I have no experience)?
A. It is not easy to put it together - this DIY project is not meant for the begginers in electronics. Try to get someone with more experience to help you.

Q. What LCD Display I must buy? With backlight?
A. You can use every Hitachi-compatible LCD - it usually has the HD44780 controller chip. Just make sure the module has 14 pins interface (or 16 pins if it has backlight).

Q. Where I can find the 16x2 LCD display (the cheaper the better)?
A. There are many, for example 73-1039-ND from

Q. J4 connector is for a pedal switch. How does this pedal works?
A. All digital switches works connecting related input to GND.

Q. How much would it cost to make this?
A. The final cost depends on the number of pads you are going to have: roughly 36 euro per pad. The eDrum controller would cost about 60 euro, box included.

Q. If I don't connect piezo to op-amps, do I have to do something else? I'll begin with only four drum pads.
A. If you don't connect piezo to an input, don 't worry, nothing happens. But, if you don't have analog board connected to J3, then connect unused inputs to AGND.

Q. The programmer you suggested have only 18-pin slot, how can I program your PIC that has 40 pins?
A. You only need to connect 5 wires, pins: Vdd, Vss, MCLR, RB6, RB7

Q. What is the role of the LED?
A. LED is on while eDrum is sending MIDI data.

Q. I donít have to buy C6,C3,U2 (max232) C5, J2,C4 even if pcb has got tracks for them. Is it correct?
A. Yes, you don't need those components. But, with new firmware, it will function as serial MIDI output (ie. for connecting to a laptop without MIDI input).