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Update mdb2pi-hat.md

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@ -95,5 +95,46 @@ mono MDBCashlessDeviceSimulatorConsole.exe /dev/serial0 115200
Hint: On newer raspbian releases, the serial port is available as /dev/serial0 - older releases may use dev/ttyAMA0.
## RTC
A PCF8563 I2C chip in conjunction with a SuperCapacitor is used for Real-Time-Clock capability (no battery required). This allows buffering of the time up to 7 days when fully charged (or even more, depending on temperature environment and chip/capacitor variance).
Read the RTC:
```bash
pi@raspberrypi:~ $ sudo hwclock -r
Thu 04 May 2017 06:22:13 UTC -0.310218 seconds
```
Write the RTC:
```bash
pi@raspberrypi:~ $ sudo hwclock -w
```
RTC Troubleshooting:
Check if the chip responds over I2C:
```bash
pi@raspberrypi:~ $ sudo i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- UU -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
```
Check dmesg for RTC
```bash
pi@raspberrypi:~ $ dmesg | grep rtc
[ 2.937443] rtc-pcf8563 1-0051: chip found, driver version 0.4.4
[ 2.943665] rtc-pcf8563 1-0051: rtc core: registered rtc-pcf8563 as rtc0
```
Hint: In case that the SuperCap has fully discharged, the daemon might be unable to talk to the RTC at first startup:
```bash
pi@raspberrypi:~ $ dmesg | grep rtc
[ 2.900119] rtc-pcf8563 1-0051: chip found, driver version 0.4.4
[ 2.900403] rtc-pcf8563 1-0051: pcf8563_write_block_data: err=-5 addr=0e, data=03
[ 2.900428] rtc-pcf8563 1-0051: pcf8563_probe: write error
[ 2.900459] rtc-pcf8563: probe of 1-0051 failed with error -5
```
In this case, please wait a few minutes to let the SuperCap being charged; then restart your pi to let the rtc daemon detect the chip again.