description for new board added

README.md

@@ -5,14 +5,11 @@ the motoserial is a phone controller
 it is used to power, flash, and communicate with Motorola C1XX phones
 the purpose is to use it for osmocomBB
 
-the USB interface will offer 4 UART ports, do communicate with 4 phones
-provide external power (4.5-5.0 V, ~2 A) so to be able to power the phone, but also be able to flash them
-
 purpose
 -------
 
 I used the osmocom baseaband software on Motorola C118 phones to monitor GSM networks
-to communicate with them, I used USB to UART converters (CP2102) on the 2.5 mm TRS jack
+to communicate with them, I used USB to UART converters (PL2302, CP2102, …) on the 2.5 mm TRS jack
 to flash the phone with the osmocomBB firmware, remove and reinstall the battery, start osmocon (or leave it running), and press on the ON button to start the bootloader
 but sometimes the software gets stuck, and for monitoring GSM networks, an automatic way to reflash the phones had to be found
 
@@ -22,10 +19,11 @@ technology
 instead of the ON button, a pin on the back of the phone can be used
 but I noticed that plugin the charger had the same effect
 and instead of the battery, a 5V power source can also be used
-so the trick is to use 2 transistors: 1 to simulate battery re-plug, and 1 to simulate charger replug; by switch off and on both power sources
+so the trick is to use 2 transistors: 1 to simulate battery re-plug, and 1 to simulate charger replug; and switch off and on both power sources
 since they share the ground pin, p-MOSFET on the positive side had to be used
 actually the order and switching timing is not too important
-thus one transistor, switching both the battery and charger power sources, is enough (and a n-MOSFET can be used)
+thus one transistor, switching both the battery and charger power sources, is enough
+this way a more common n-channel MOSFET can be used, but the groung pin of serial should then also ne switched
 
 the battery can be replaced by a regular 5 V power source, the same as the one used for charging
 if the voltage is above 4.2 V, the battery should not be charged
@@ -45,53 +43,63 @@ hardware
 files
 -----
 
-motoserial-phone:
-the battery replacement
-provide 5 V (~1 A) input power
-the other port is to forward this power to the charger
-the PCB will replace and provide power instead of the battery
-a diode is used to prevent revers current when charging
-capacitors are necessary to cope with the peak power usage when the phone transmits
-
-motoserial-spare:
-this is the USB to 4 UART + power controller board
-it uses spare parts from my component stock (mainly the expensive FT4232H)
+motoserial:
+after several prototypes (see versions), this was the best solution
+the PCB replaces the battery
+I had too many missing or dead batteries (which will start charging only after 30 minutes, and only lasts 10 minutes)
+large capacitors compensate for the large but brief power surges during transmition bursts
+connect the PCB to the computer through a USB to UART converter with the following pins: 5V, TX, RX, DTR, GND
+a good USB to UART converter would be the Silicon Labs CP2102 (or CP2104)
+they handle baudrates slightly different from standard values (which the Mototola C1XX have) better than Prolific PL2303, but not as good than FTDI FT2232R
+they are more expensive than Prolific PL2303 converters, but cheaper than FTDI FT2232R, and work quite fine
+good and cheap converters are BAITE (betemcu.cn) BTE13-007, CNT-003, or B75937 (solder pin DTR)
+the DTR (or RTS) signal is used control the power switch
+CP2102 resets this signal when the serial connection is closed
+FT2232R can only reset RTS once the option is set in EEPROM, but DTR goes and stays low the first time the serial port is opened
+CP2102 also includes a 700 mA resetable switch on the 5V pin which will prevent draining too much power on the USB port
+connect the UART port to a 2.5mm TRS stereo jack and plug it in the headphone to be able to flash and communicate with the phone
+connect the CHG port to a jack barrel (1.1mm inner diameter and 3.0 mm outer diameter) and plug it in the charger port to able to start the phone
+some phones also provides these pind on the back, but not all
+only though hole components have been used because it could not be all SMD (large capacitors are very expensive, and header connections to weak)
+this allows to have a single sided PCB which can also be produced in amateur labs
 
 version
 -------
 
 0:
-working version
+current working version
+
+E:
+now motoserial-phone version prototype built (also provides a UART port)
+bugs:
+- resistors are in the way of connections
+- pull-up/limiting resistor misplaced. the nMOS gate oscillates around Vgs
+
+D:
+4 motoserial-phone prototypes built to work with the motoserial-cape
+bugs:
+- the central tab is a bit too long. it's hard to remove the battery
+
+C:
+second motoserial-cape prototype built
+bugs:
+- one ground copper connection in the plane cut because too thin
+- 100nF dim the UART signals and should be removed
+
+B:
+first motoserial-cape (for BeagleBoard BeagleBone Black) prototype built
+bugs:
+- I used nMOS instead of pMOS, which won't work because the power connection on the phone shares ground with UART
+
 
 A:
-first scrape prototype built using CircuitPro + ProtoMat S63
+first motoserial-scrape prototype built using CircuitPro + ProtoMat S63
 bugs:
-- the hole for the USB and header pins are too wide. I hope it would create some through hole plating thanks to capillarity, but it didn't
+- the hole for the USB and header pins are too wide. I hoped it would create some through hole plating thanks to capillarity, but it didn't
 - wider vias annulus would be a good idea
 - DTR it set (to low) when the serial port is opened, but is no reset (to high) when closed (FT4232H specific)
 - RTS can be reset to high on close, but that need to be programmed in the FT4232H's EEPROM
 - the 3.3 V on DTR can not drive the pMOS because it's switching 5.0 V, but V_GS < 1.1 V
 - decoupling capacitors on the serial lines should improve the quality
 - try if with less feritte beads and decoupling capacaitors PLL still works
-
-B:
-first cape prototype built using CircuitPro + ProtoMat S63
-bugs:
-- I used nMOS instead of pMOS, which won't work because the power connection on the phone shares ground with UART
-
-C:
-second cape prototype built, using CircuitPro + ProtoMat S63
-bugs:
-- one ground copper connection in the plane cut because too thin
-- 100nF dim the UART signals and should be removed
-
-D:
-4 phone prototypes built to work with the cape
-bugs:
-- the central tab is a bit too long. it's hard to remove the battery
-
-E:
-now phone version prototype built
-bugs:
-- resistors are in the way of connections
-- pull-up/limiting resistor misplaced. the nMOS gate oscillates around Vth
+- Silabs CP2108 would be cheaper and easier to use than FT4232H