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Version 1.0 of the board contains the following bugs:
The changes are documented in version 1.1 and 1.2, however no such new PCB has been produced.
1. TWI
Problem: TWI misses the ~2k pull up resistors on both signals.
Workaround: Use TWI with internal 20k pull-up resistors. This will only work on very low clock frequencies.
2. Light sensor
To measure the full dynamic of the surrounding, different values for R2 are needed.
Workaround: Use R2 = 1MOhm, and connect PE4 with 100kOhm and PE7 with 4.7kOhm to the photo transistor.
Note: Due connection of R2 with R5, measurements with PE4 or PE7 as high, must remove the effects of T1 by measuring T1 and do some math.
3. JTAG
The connector is too close to J4.
Workaround: Use PDI for programming or do not equip J4.
Note: JTAG has never been tested.
4. Jumpers J1, J2, J3, J4
4.1 The jumpers are lager than expected. Text in front can't be read. Workaround: None
4.2 D4 has too less space. Workaround: Solder D4 from the bottom
5. LED Voltage regulator
5.1 Disconnecting the power supply by opening SV9, results in VCC as VCCLED. TOO HIGH VOLTAGE! Workaround: Never open SV9 unless all matrix LEDs are off. Only open tesing purpose (eg measuring current consumptions).
5.2 C18 makes regulation bad. Workaround: Don't equip C18.
5.3 Regulation swings. Workaround: Connect 100nF from VCCLED to the positive input of IC2.
5.4 Regulation swings. C20 is too small. Use at least 150µF. Connect an additional electrolyte in parallel.
5.5 The planned 30Ohm as resistor for the LEDs cant be bought easily. Workaround: Use 27Ohm.
6. Touch
Do not equip C23 ... C30.
Sensitivity too low. Make PCB sensing field larger. Or better use IR distance sensors (other .brd file)
7. Level converter for PDI bad.
Workaround: Do not equip SV8, D1, D2. Lower R3, R4 to 200Ohm. Use 3.3V programmer.
8. Too high power consumption
Do not equip D3.
9. Screw holes
The screw holes are too close to some pads.
Workaround: Do not use or use isolated screws.
10. Crystals
10.1 There are vias below Q1 ans Q2 which may result in a short circuit if the crystal touches these.
Workaround: Solder pins of Q1 with some distance to the PCB. Add some isolating tape below Q2.
10.2 C10 and C11 are not needed. Do not equip.
11. SV4
The holes only allow soldering female header and are too small for male header.
Workaround: Use female header.
12. RFM12:
12.1 There are vias below the RFM12 module wich might result in short circuit
Workaround: Put a piece of paper between pcb and RFM12 while soldering, remove later -> results in some space between PCBs
12.2 RFM12 needs external reset for proper operation
Woraround: Connect pin PE5 from PIR detector to reset (do not use PIR detector)
13. PIR Detector does not work
Workaround: Do not solder PIR detector and R39
14. R42 and R43 are too low, resulting in a maximum voltage measurement range of 3.2V -> not enough for charger
Workaround: Solder 360kOhm for both resistors
15. Charging current cant be measured very well
Use 2.2Ohm for R46.
==ir-sensor==
16. The ir-sensor board uses SG2-BC photointerrupters as contact-free keys. However direct sunlight results in accidential key presses and intentional key presses become impossible.
Workaround: Only use clock in the shadow from the sun or with artifical light.
==touch-sensor==
17. The Diodes D1-D8 in the PCB are difficult to solder when C1-C4 are already soldered.
Workaround: Solder D1-D8 before soldering C1-C4.
==Voltage limit==
18. The 75k potentiometer is difficult to buy.
Workaround: Use 100k
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