Expansion header and hardware test/access points

DXF of board layout for mechanical dims

PIC32MX1xx datasheet

PIC32MX1xx errata

Expansion header pins

Pin	Function	Comments. See Datasheet section 11.3 for pin remapping details. Only functions that don't clash with existing badge functionality are listed below. IC - input capture, OC = Output compare (e.g.  PWM)
1	0V	Ground. Also on ISP header pin 3 and TTL232 header pin 1 Also available on several pads around prototype area
2	I2C SDA	2.8v levels. Used onboard by accelerometer and camera Also available at edge of prototyping area
3	I2C SCL	2.8v levels Used onboard by accelerometer and camera Also available at edge of prototyping area
4	+2.8V	Logic supply. Also on ISP header pin 2 Also available at edge of prototyping area
5	RA2/RPA2	PIC pin 30. I/O or mappable peripheral RPA2 Set to output by default RPA2 can be mapped to inputs INT2,T4CK,IC1,IC5,OCFB, and outputs SDO1,SDO2,OC4,OC5,REFCLKO
6	RB4/RPB4	PIC Pin 33. I/O or mappable peripheral RB4 Set to output by default. RPB4 can be mapped to inputs INT4,T2CLK,IC4,REFCLKI and outputs U1TX,OC1,C2OUT
7	RB0/RPB0/PGD1/AN2	PIC pin 21. I/O or remappable peripheral Configured as UART2 TXD by default. Also on ISP header pin 4 and TTL232 header pin 5 Shared with ISP, so add at least 2K2 in series if driving pin to avoid interfering withe programming functionality. RPB0 can be mapped to inputs INT1,T5CK,IC2,OCFA and outputs U2TX,OC3,C1OUT Analogue channel 2 ( need to set ANSELB bit 0)
8	RC5/RPC5	PIC pin 38. I/O or remappable peripheral. 5V Tolerant. Configured as output by default. Reconfigured as UART1 TXD the first time u1txbyte() is called. Note as this pin is shared with PMA3, it is subject to device errata. TL;DR : no problems if used as mappable peripheral or input, but to use as output you need to set the corresponding bit in PMAEN and write the output value to PMADDR instead of LATC  RPC5 can be mapped to inputs INT4,T2CK,IC4,REFCKI and outputs U1TX,OC1,C2OUT
9	+3.3V	Output of 3.3v boost regulator. Note that if the incoming supply is >3.3v, this pin will rise to the input voltage!
10	RC3/RPC3	PIC pin 36 Configured as input with pullup by default. UART1 RXD by default. Reconfigured as UART1 RXD the first time u1txbyte() is called. RPC3 can be mapped to inputs INT2,T4CK,IC1,IC5,U1RX,SDI2 and outputs SDO1,SDO2,OC4,OC5,REFCLKO
11	VBAT	Unswitched battery supply
12	RB1/RPB1/PGC1/AN3	PIC pin 22 Configured as UART2 RXD by default. Also on ISP header pin 5 and via 2k2 resistor R10 to TTL232 pin 4 Shared with ISP, so add at least 2K2 in series if driving pin to avoid interfering with  programming functionality. RPB1 can be mapped to inputs INT3,T3CK,IC3,U2RX,SDI1 and outputs SDO1,SDO2,OC2,C3OUT. Analogue channel 3 ( need to set ANSELB bit 1)

Power
Sugested maximum draw from +3.3v or +2.8v is 200mA, maybe 300mA for brief periods.
If the OLED starts dimming, you're pulling too much!
Power may be fed into VBAT if batteries are not fitted, however note that if the supplied voltage exceeds 3.3v, the 3.3v rail will output the incoming supply voltage. This is not a problem for the badge up to about 5V, but be aware of possible dissipation issues in the 2.8v regulator if you are also pulling a lot from 2.8v.
If you have 3.3v -only devices and want to supply from >3.3v ( e.g. lipo), you should use your own 3.3v regulator. You can use the 2.8V rail as an enable to switch your local 3.3v supply if needed.

Firmware support for hardware

All I/O used by the badge is intialised in inithardware() in hardware.c

UARTs :

u1txbyte(c) and u2txbyte(c) Send 1 byte to UART1 and UART2 respectively. Baudrates are initialised with values in cambadge.h
UART1 is not mapped to pins at startup, but is mapped, and the UART configured, on the first call to u1txbyte()
A simple receive handler is set up for UART2 - this is in serial.c - see code for more details.

I2C :

On-board I2C device addresses : Camera 0x60 Accelerometer 0x3A (8  bit addresses).

The accelerometer is read on every 20mS tick period. 

The following routines are provided for I2C access. See globals.h for more info

unsigned int iistart(unsigned char iiadr)  Starts I2C command, iiadr - device address ( 8 bit). Returns zero if device does't acknowledge
unsigned int iisend(unsigned char byte) Sends 1 byte, returns zero if no acknowledge
void iirestart(unsigned char iiadr) Send Restart condition for read operationunsigned
int getiic(unsigned int ack) Read 1 byte, ack=1 to acknowledge ( set to 0 for last byte ).
void iistop(void)   Send I2C stop condition

Accessing hardware directly

I/O ports :

Set bit 2 on PORTA : LATASET=1<<2
Clear bit 2 on PORTA : LATACLR=1<<2
Invert bit 2 on PORTA : LATAINV=1<<2
Read bit 2 on PORTA : a=PORTAbits.RA2
Set bit 2 on PORTA to input ( output) TRISAbits,TRISA2=1 (0)
Write bit<value> to PORTA bit 2 : LATAbits.LATA2=<value>

Some peripheral functions can be mapped to RxP pins - see the "Peripheral Pin Select" section in the PIC datasheet.
e.g. to put Output Compare 4 on RA2 : 

RPA2Rbits.RPA2R=5;  // 5 is OC4 from Table 11-2 in datasheet

To set input capture 1 on RA2 : 

IC1Rbits.IC1R=0; // 0 is RA2 from Table 11-1 in datasheet

See hardware.c for more examples.

PIC resources used by badge firmware

Items marked * are used within the main polling loop. Others are only used by applications and may be used by other applications with care if their other functions are not being used.

ADC* : battery read.
Parallel Master Port : Camera.
I2C2* : Camera and accelerometer
Timer 1 : Used for delays via delayus()
Timer 2 : Used by camera and browser applications for frame-rates
Timer 3 : Used by camera capture task to count pixel clocks
Timer 4* : Used for system tick
REFO : Used to clock camera ( do not disable - camera will screw up I2C bus)
SPI1 : Display
SPI2 : SD card and SRAM
UART1 : Can be used for debug output
UART2 : Debug output and serial remote control