Raspberry Pi DV

The design of the Raspberry Pi version of the GMSK board is very similar to the one for the Arduino. The main difference is that the Arduino runs at 5V compared to the 3.3V for the Pi.

Broadcom kernel driver bugs

There are some problems with the Broadcom device drivers supplied for the Pi. The issue is that while the Broadcom chip can handle hardware interrupt queuing, the device driver doesn't do any queuing. This means that when the software is in an interrupt service routine, any other interrupt will be lost. Since there are a number of interrupt sources the interrupts from the RasPi DV board are often lost. In practice if only transmit or receive mode is turned on, about one out of every 50 interrupts is lost. This is WAY too many bits to lose in a D-Star stream. When contacted about the bugs, Broadcom declined to help fix the drivers. There have been a few posts in the Pi online forums here and here about the problem and what things have already been tried to fix it. So far nothing has worked.

Raspberry Pi DV adapter board

After spending months working on a custom device driver to support the RasPi DV board and to try and find workarounds for the Broadcom bugs, it was decided to try to build an adapter board to give the functionality of an Arduino to handle the interrupts. This adapter board works well with the existing RasPi DV boards that have already been built. The design was then combined to create the RasPi DV AVR board.

GPIO Connector pinout

The RasPi DV board connects directly to the GPIO pins of the Raspberry Pi.

Pin Number	Pin Name Rev1	Pin Name Rev2	RasPi DV Pin Name
01	3.3 V	3.3 V
02	5V0	5V0	5V0
03	GPIO 0	GPIO 2
04	5V0	5V0	5V0
05	GPIO 1	GPIO 3
06	GND	GND	GND
07	GPIO 4	GPIO 4	PLLACQ
08	GPIO 14	GPIO 14
09	GND	GND	GND
10	GPIO 15	GPIO 15
11	GPIO17	GPIO17	COS
12	GPIO 18	GPIO 18
13	GPIO21	GPIO27	COS_LED
14	GND	GND	GND
15	GPIO22	GPIO22	PTT
16	GPIO23	GPIO23	RX_SN
17	3.3 V	3.3 V
18	GPIO24	GPIO24	TXCLK
19	GPIO10	GPIO10
20	GND	GND	GND
21	GPIO9	GPIO9
22	GPIO25	GPIO25	RXCLK
23	GPIO11	GPIO11
24	GPIO08	GPIO08	RXDATA
25	GND	GND
26	GPIO07	GPIO07	TXDATA

Schematics

The schematic diagrams and PCB layouts were done using Eagle CAD. They offer a limited free version of the software available for Windows, Mac and Linux. The PDFs of the schematic diagrams can be found on the downloads page.

Ordering components

For the most part, all the parts are available from either Mouser and/or Tayda Electronics. The PCBs can come from a service such as OSH Park or Seeed Studio.The prices below are based on purchasing enough parts in bulk to make kits for at least 10 boards. Buying the parts for just a single board would cost quite a few dollars more. The pricing for the resistors and capacitors is based on buying at least multiples of 100 at a time. The pricing for parts at Tayda assumes using 15% discount they regularly post on their Facebook page.

RasPi DV Bill of Materials

Category	Description	Qty	Designators	Price	Ext	Vendor link
Semiconductors
	CMX589AE2	1	U1	$3.700	$3.700	eBay
	MCP6002-I/MS	1	U2	$0.330	$0.330	Mouser
	LD1117-33	1	U3	$0.271	$0.271	Mouser
	IRLML2060	1	Q3	$0.149	$0.149	Mouser
	2N7002	1	Q5	$0.034	$0.034	Tayda
LEDs
	LED G	1	D1	$0.051	$0.051	eBay
	LED Y	1	D2	$0.054	$0.054	eBay
	LED R	1	D3	$0.051	$0.051	eBay
Crystals
	4.9152MHz	1	Y1	$0.330	$0.330	Mouser
Capacitors
	22pF (22)	1	C6	$0.008	$0.008	Tayda
	30pF (30)	2	C2, C3	$0.071	$0.142	Mouser
	470pF (471)	3	C1, C9, C16, C17	$0.008	$0.024	Tayda
	27nF (273)	2	C7, C8	$0.100	$0.200	Mouser
	.1uF (104)	5	C4, C10, C12, C14	$0.008	$0.040	Tayda
	1uF (105)	4	C5, C11, C13, C15	$0.037	$0.148	Mouser
Resistors
	200K potentiometer	1	Rx	$0.162	$0.162	Tayda
	50K potentiometer	1	Rx (alternate)	$0.162	$0.162	Tayda
	500K potentiometer	1	Tx	$0.162	$0.162	Tayda
	100K potentiometer	1	Tx (alternate)	$0.162	$0.162	Tayda
	330	2	R21, R23	$0.008	$0.016	Tayda
	2.7k	3	R22, R26, R27	$0.008	$0.024	Tayda
	47k	5	R5, R6, R8, R9, R10, R14	$0.008	$0.040	Tayda
	100k	6	R1, R3, R4, R12, R13, R25	$0.008	$0.048	Tayda
	1M	2	R2, R24	$0.008	$0.016	Tayda
Connectors
	2x3 conn	1	JP2	$0.025	$0.025	Tayda
	2x13 conn	1	JP1	$0.187	$0.187	Tayda
PCB
	2 sided PCB	1		$0.825	$0.83	Seeed Studio
	2 sided PCB - Qty 3	1		$9.95	$9.95	OSHPark
Shipping
	Mouser	1		$0.675	$0.68
	Seeed	1		$1.000	$1.00
	Tayda	1		$0.280	$0.28
Total					$6.91

RasPi DV I/F Adapter Bill of Materials

Category	Description	Qty	Designators	Price	Ext	Vendor link
Semiconductors
	BS108ZL1G	2	Q5, Q6	$0.345	$0.690	Mouser
	ATMEGA328P-PU	1	U1	$2.940	$2.940	Mouser
LEDs
	LED Yellow	1	D1	$0.017	$0.017	Tayda
	LED Green	1	D2	$0.017	$0.017	Tayda
Crystals
	16.000MHz	1	Y1	$0.085	$0.085	Tayda
Capacitors
	30pF (30)	2	C6, C7	$0.008	$0.016	Tayda
	27nF (273)	2	C4, C5	$0.008	$0.016	Tayda
	.1uF (104)	1	C1	$0.008	$0.008	Tayda
	1uF (105)	1	C2	$0.088	$0.088	Mouser
Resistors
	1.5K	1	R21	$0.009	$0.009	Tayda
	2.7K	3	R1, R6, R17	$0.009	$0.027	Tayda
	3.3K	1	R22	$0.009	$0.009	Tayda
	10K	4	R19, R20, R23, R24	$0.009	$0.036	Tayda
	1M	1	R13	$0.008	$0.009	Tayda
Connectors
	2x13 conn (M)	1	JP2	$0.130	$0.130	Tayda
	2x13 conn (F)	1	JP1	$0.180	$0.180	Tayda
	28 pin DIP socket	1	U1	$0.187	$0.187	Tayda
PCB
	2 sided PCB	1		$0.825	$0.825	Seeed Studio
	2 sided PCB - Qty 3	1		$6.067	$6.067	OSHPark
Shipping
	Mouser	1		$0.675	$0.680
	Seeed	1		$1.000	$1.000
	Tayda	1		$0.280	$0.280
Total					$7.249