Two of the pins in header J401 can be used for external voltage measurements, however only one at the time. The possible voltage ranges are 0 to VCC or via a voltage divider giving an approximate range of 0 to five times VCC. A simple voltage divider is implemented to scale the measurement voltage. A diode bridge is also used to prevent reverse polarity and to protect the ATmega3290P's ADC channel 3.
GPIO
Both the ATmega3290P and ATmega1284P are high pin count devices, and a number of these are not used. These pins are available through the user IO headers; J401, J201, J202 and J203. See Table 3-2 and Table 3-3 for further details.
Be aware that these pins do not have level converters and should thus not be connected directly to an application board running on a different voltage level than the AVRRAVEN.
| ATMega3290P port pin | PCB Connection | Comment |
|---|---|---|
| PE3 | J401-8 | Via 470Ω series resistor and 10kΩ pull-up |
| PE4 | J401-9 | Via 470Ω series resistor and 10kΩ pull-up |
| PE5 | J401-10 | Via 470Ω series resistor and 10kΩ pull-up |
| PE6 | J401-11 | Via 470Ω series resistor and 10kΩ pull-up |
| ATMega1284P port pin | PCB Connection | Comment |
|---|---|---|
| PC0 | J201-1 | TWI SCL. Connected to serial EEPROM |
| PC1 | J201-2 | TWI SDA. Connected to serial EEPROM |
| PC2 | J201-3 | JTAG TCK. |
| PC3 | J201-4 | JTAG TMS. |
| PC4 | J201-5 | JTAG TDO. |
| PC5 | J201-6 | JTAG TDI. |
| N.C. | J201-7 | Populate R204 to connect to PC6. RTC Xtal XC202 must then be removed. |
| N.C. | J201-8 | Populate R205 to connect to PC6. RTC Xtal XC202 must then be removed. |
| PD0 | J202-1 | RXD0 Inter processor communication. |
| PD1 | J202-2 | TXD0 Inter processor communication. |
| PD2 | J202-3 | DIO or RXD1. |
| PD3 | J202-4 | DIO or TXD1. |
| PD4 | J202-5 | DIO. |
| PD5 | J202-6 | DIO. |
| PB2 | J202-7 | DIO. NB: NOT PD6! |
| PD7 | J202-8 | DIO. |
| PA0 | J203-1 | DIO or ADC Channel 0. |
| PA1 | J203-2 | DIO or ADC Channel 1. |
| PA2 | J203-3 | DIO or ADC Channel 2. |
| PA3 | J203-4 | DIO or ADC Channel 3. |
| PA4 | J203-5 | DIO or ADC Channel 4. |
| PA5 | J203-6 | DIO or ADC Channel 5. |
| PA6 | J203-7 | DIO or ADC Channel 6. |
| PA7 | J203-8 | DIO or ADC Channel 7. |
| Additional interfaces | PCB Connection | Comment |
| External power | J201-10 J202-10 J203-10 | Connected to J401-1 |
| 0V | J201-9 J202-9 J203-9 | Connected to J401-2 |